HashMap.java

import java.util.*;
import java.util.Map.Entry;

public class HashMaped {
    public static void main(String[] args) {
        HashMap<String, Integer> mymap = new HashMap<>();

        // Insertion or addition in hashmap
        mymap.put("CSE", 455055);
        mymap.put("ece", 2000);
        System.out.println(mymap); // {CSE=455055, ece=2000}

        // Accessing the value from the hashmap
        int data = mymap.get("CSE");
        System.out.println(data);

        // Find the particular key exist or not
        if (mymap.containsKey("CSE")) {
            System.out.println("Key Exist:: " + mymap.get("CSE"));
        } else {
            System.out.println("There is no key exist");
        }

        // Find the particular value exist or not
        if (mymap.containsValue(455055)) {
            System.out.println("Value Exist:: ");
        } else {
            System.out.println("There is no value exist");
        }

        // NEW KEY WILL BE NOT CREATED IF KEY ALREADY EXIST IT WILL REPLACE THE VALUE
        mymap.put("CSE", 12345);
        System.out.println(mymap);


        // delete the key
        mymap.remove("ece");
        System.out.println(mymap);

        // keySet

        mymap.put("mec", 12122);
        mymap.put("bio", 1232);;
        mymap.put("pharma", 122122);;
        mymap.put("civil", 1232);;
        System.out.println(mymap.keySet());

        // Iterate get(key)
        // for( String key: mymap.keySet()) {
        //     System.out.println(key+ "  "+ mymap.get(key));
        // }
         
        // iterate entry set
        // Entry<String , Integer> it : mymap.entrySet();
         for(Entry<String, Integer> it: mymap.entrySet()) {
            System.out.println(it);

         }
          

         // Iterate through value
         for(int value: mymap.values()) {
            System.out.println(value);
         }

    }
}

// HashMap does not support duplicate key.
// Hash map support duplicate value
// time complexity 
// faster 
// it store the key value pair