HashMap putIfAbsent(K, V) in Java

putIfAbsent(K, V): This method is available in java.util.HashMap class of Java.

Syntax:

V java.util.HashMap.putIfAbsent(K key, V value)

This method takes two arguments. If the specified key is not already associated with a value associates it with the given value and returns null, else returns the current value.

Parameters: Two parameters are required for this method.

key: key with which the specified value is to be associated.

value: value to be associated with the specified key.

Returns: the previous value associated with the specified key, or null if there was no mapping for the key.

Exceptions: NA

Approach

Java

import java.util.HashMap;

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

        hashMap.put("Hello", 1);
        hashMap.put("World", 2);

        hashMap.putIfAbsent("Java", 3);

        System.out.println(hashMap);

    }
}

Output:

{Java=3, Hello=1, World=2}