Home » Java programming language

Java IdentityHashMap putAll() Method with Example

IdentityHashMap Class putAll() method: Here, we are going to learn about the putAll() method of IdentityHashMap Class with its syntax and example.
Submitted by Preeti Jain, on March 06, 2020

IdentityHashMap Class putAll() method

• putAll() method is available in java.util package.
• putAll() method is used to copy all of the entry (key-value pairs) that exists from the given map (m) and paste it into this IdentityHashMap.
• putAll() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• putAll() method may throw an exception at the time of copying key-value pairs.
  NullPointerException: This exception may throw when the given parameter is null exists.

Syntax:

    public void putAll(Map m);

Parameter(s):

• Map m – represents the Map object that contains key-value pairs to be copied from.

Return value:

The return type of the method is void, it returns nothing.

Example:

// Java program to demonstrate the example 
// of void putAll(Map m) method of IdentityHashMap 

import java.util.*;

public class PutAllOfIdentityHashMap {
    public static void main(String[] args) {
        // Instantiates a IdentityHashMap object
        Map < Integer, String > map = new IdentityHashMap < Integer, String > ();
        Map < Integer, String > put_map = new IdentityHashMap < Integer, String > ();

        // By using put() method is to add
        // key-value pairs in a IdentityHashMap
        map.put(10, "C");
        map.put(20, "C++");
        map.put(50, "JAVA");
        map.put(40, "PHP");
        map.put(30, "SFDC");

        // Display IdentityHashMap
        System.out.println("IdentityHashMap: " + map);

        // By using putAll() method is to
        // copy all of the elements of the given
        // object and paste it in an another object

        put_map.putAll(map);

        // Display put_map IdentityHashMap
        System.out.print("put_map.putAll(map): " + put_map);
    }
}

Output

IdentityHashMap: {20=C++, 40=PHP, 50=JAVA, 30=SFDC, 10=C}
put_map.putAll(map): {20=C++, 40=PHP, 50=JAVA, 30=SFDC, 10=C}