WeakHashMap replace(K, V, V) in Java

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

Syntax:

boolean java.util.Map.replace(K key, V oldValue, V newValue)

This method takes three arguments. This method replaces the entry for the specified key only if currently mapped to the specified value.

Parameters: Three parameters are required for this method.

key: key with which the specified value is associated.

oldValue: value expected to be associated with the specified key.

newValue: value to be associated with the specified key.

Returns: true if the value was replaced.

Throws:

1. UnsupportedOperationException - if the put operation is not supported by this map.

2. ClassCastException - if the class of a specified key or value prevents it from being stored in this map.

3. NullPointerException - if a specified key or newValue is null, and this map does not permit null keys or values.

4. IllegalArgumentException - if some property of a specified key or value prevents it from being stored in this map.

Approach

Java

import java.util.WeakHashMap;

public class WeakHashMapreplace2 {
    public static void main(String[] args) {

        WeakHashMap<String, Integer> weakHashMap = 
                   new WeakHashMap<String, Integer>();

        weakHashMap.put("Java", 1);
        weakHashMap.put("Hello", 2);

        String key = "Java";
        Integer oldValue = 1, newValue = 3;

        System.out.println(weakHashMap.replace(key, 
                                     oldValue, newValue));

    }
}

Output:

true