Add PathUtils.getExtension(Path)

apache · Dec 23, 2023 · ce52198 · ce52198
1 parent b059cd3
commit ce52198
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diff --git a/src/changes/changes.xml b/src/changes/changes.xml
@@ -90,6 +90,7 @@ The <action> type attribute can be add,update,fix,remove.
       <action dev="ggregory" type="add"                due-to="Gary Gregory">Add FileTimes.isUnixTime(long).</action>
       <action dev="ggregory" type="add"                due-to="Gary Gregory">Add FileTimes.toUnixTime(FileTime).</action>
       <action dev="ggregory" type="add"                due-to="Gary Gregory">Add BrokenInputStream.Builder.</action>
+      <action dev="ggregory" type="add"                due-to="Gary Gregory">Add PathUtils.getExtension(Path).</action>
       <!--  UPDATE -->
       <action dev="ggregory" type="fix"                due-to="Gary Gregory">Bump commons.bytebuddy.version from 1.14.10 to 1.14.11 #534.</action>
     </release>

diff --git a/src/main/java/org/apache/commons/io/file/PathUtils.java b/src/main/java/org/apache/commons/io/file/PathUtils.java
@@ -867,6 +867,32 @@ public static DosFileAttributeView getDosFileAttributeView(final Path path, fina
         return Files.getFileAttributeView(path, DosFileAttributeView.class, options);
     }
 
+    /**
+     * Gets the extension of a Path.
+     * <p>
+     * This method returns the textual part of the Path after the last dot.
+     * </p>
+     * <pre>
+     * foo.txt      --&gt; "txt"
+     * a/b/c.jpg    --&gt; "jpg"
+     * a/b.txt/c    --&gt; ""
+     * a/b/c        --&gt; ""
+     * </pre>
+     * <p>
+     * The output will be the same irrespective of the machine that the code is running on.
+     * </p>
+     * <p>
+     *
+     * @param path the path to query.
+     * @return the extension of the file or an empty string if none exists or {@code null}
+     * if the fileName is {@code null}.
+     * @since 2.16.0
+     */
+    public static String getExtension(final Path path) {
+        final String fileName = getFileNameString(path);
+        return fileName != null ? FilenameUtils.getExtension(fileName) : null;
+    }
+
     /**
      * Gets the Path's file name and apply the given function if the file name is non-null.
      *

diff --git a/src/test/java/org/apache/commons/io/file/PathUtilsTest.java b/src/test/java/org/apache/commons/io/file/PathUtilsTest.java
@@ -246,6 +246,32 @@ public void testCreateDirectoriesSymlinkClashing() throws IOException {
         assertEquals(symlinkedDir, PathUtils.createParentDirectories(symlinkedDir.resolve("child")));
     }
 
+    @Test
+    public void testGetExtension() {
+        assertNull(PathUtils.getExtension(null));
+        assertEquals("ext", PathUtils.getExtension(Paths.get("file.ext")));
+        assertEquals("", PathUtils.getExtension(Paths.get("README")));
+        assertEquals("com", PathUtils.getExtension(Paths.get("domain.dot.com")));
+        assertEquals("jpeg", PathUtils.getExtension(Paths.get("image.jpeg")));
+        assertEquals("", PathUtils.getExtension(Paths.get("a.b/c")));
+        assertEquals("txt", PathUtils.getExtension(Paths.get("a.b/c.txt")));
+        assertEquals("", PathUtils.getExtension(Paths.get("a/b/c")));
+        assertEquals("", PathUtils.getExtension(Paths.get("a.b\\c")));
+        assertEquals("txt", PathUtils.getExtension(Paths.get("a.b\\c.txt")));
+        assertEquals("", PathUtils.getExtension(Paths.get("a\\b\\c")));
+        assertEquals("", PathUtils.getExtension(Paths.get("C:\\temp\\foo.bar\\README")));
+        assertEquals("ext", PathUtils.getExtension(Paths.get("../filename.ext")));
+
+        if (File.separatorChar == '\\') {
+            // Special case handling for NTFS ADS names
+            final IllegalArgumentException e = assertThrows(IllegalArgumentException.class, () -> PathUtils.getExtension(Paths.get("foo.exe:bar.txt")));
+            assertEquals("NTFS ADS separator (':') in file name is forbidden.", e.getMessage());
+        } else {
+            // Upwards compatibility:
+            assertEquals("txt", PathUtils.getExtension(Paths.get("foo.exe:bar.txt")));
+        }
+    }
+
     @Test
     public void testGetFileName() {
         assertNull(PathUtils.getFileName(null, null));