Java Utility Library

Java HashMap - replace() Method

The java.util.HashMap.replace() method is used to replace the entry for the specified key only if it is currently mapped to the specified value.

Syntax

public boolean replace(K key, V oldValue, V newValue)

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

Parameters

`key`	Specify the key with which the specified value is associated.
`oldValue`	Specify value expected to be associated with the specified key.
`newValue`	Specify value to be associated with the specified key.

Return Value

Returns true if the value was replaced.

Exception

NA.

Example:

In the example below, the java.util.HashMap.replace() method is used to replace the entry for the specified key in the given map.

import java.util.*;

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

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

    //printing MyMap
    System.out.println("Before replace, MyMap contains: " + MyMap);    

    //replacing the value associated with 101 key
    MyMap.replace(101, "John", "Sam");
    //replacing the value associated with 102 key
    //it is not replaced as oldValue is not matching
    MyMap.replace(102, "Jo", "Peter");     

    //printing MyMap
    System.out.println("After replace, MyMap contains: " + MyMap);  
  }
}

The output of the above code will be:

Before replace, MyMap contains: {101=John, 102=Marry, 103=Kim}
After replace, MyMap contains: {101=Sam, 102=Marry, 103=Kim}

❮ Java.util - HashMap