java.util.IdentityHashMap.putAll() Method


The putAll(Map<? extends K,? extends V> t) method is used to copy all of the mappings from the specified map to this map.


Following is the declaration for java.util.IdentityHashMap.putAll() method.

public void putAll(Map<? extends K,? extends V> t)


t − This is the mappings to be stored in this map.

Return Value

The method call returns the previous value associated with key, or null if there was no mapping for key.


NullPointerException − This is thrown if the specified map is null.


The following example shows the usage of java.util.IdentityHashMap.putAll()

package com.tutorialspoint;

import java.util.*;

public class IdentityHashMapDemo {
   public static void main(String args[]) {

      // create 2 identity hash maps
      IdentityHashMap ihmap1 = new IdentityHashMap();
      IdentityHashMap ihmap2 = new IdentityHashMap();

      // populate the ihmap1
      ihmap1.put(1, "java");
      ihmap1.put(2, "util");
      ihmap1.put(3, "package");

      System.out.println("Value of ihmap1 before: " + ihmap1);
      System.out.println("Value of ihmap2 before: " + ihmap2);

      // put all values from ihmap1 to ihmap2

      System.out.println("Value of ihmap2 after: " + ihmap2);

Let us compile and run the above program, this will produce the following result.

Value of ihmap1 before: {2=util, 3=package, 1=java}
Value of ihmap2 before: {}
Value of ihmap2 after: {2=util, 3=package, 1=java}
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