Java IdentityHashMap - put() Method

The java.util.IdentityHashMap.put() method is used to map the specified key to the specified value in the identity hash map. If the key is already present in the map, the old value is replaced.

Syntax

public V put(K key, V value)

Here, K and V are the type of key and value respectively maintained by the container.

Parameters

Return Value

Returns the previous value associated with key, or null if there was no mapping for key. (A null return can also indicate that the map previously associated null with key.)

Exception

NA

Example:

In the example below, the java.util.IdentityHashMap.put() method is used to map the specified key to the specified value in the given identity hash map.

import java.util.*;

public class MyClass {
  public static void main(String[] args) {
    //creating a identity hash map
    IdentityHashMap<Integer, String> MyMap = new IdentityHashMap<Integer, String>();

    //populating the map
    MyMap.put(101, "John");
    MyMap.put(102, "Marry");
    MyMap.put(103, "Kim");
    MyMap.put(104, "Jo");

    //printing the map
    System.out.println("MyMap contains: " + MyMap);    

    //change a key-value pair
    MyMap.put(103, "Ramesh"); 

    //printing the map
    System.out.println("MyMap contains: " + MyMap);  
  }
}

The output of the above code will be:

MyMap contains: {102=Marry, 104=Jo, 103=Kim, 101=John}
MyMap contains: {102=Marry, 104=Jo, 103=Ramesh, 101=John}