WeakHashMap remove() method in Java

Last Updated : 20 Jul, 2018

The java.util.WeakHashMap.remove() is an inbuilt method of WeakHashMap class and is used to remove the mapping of any particular key from the map. It basically removes the values for any particular key in the Map.

Syntax:

Weak_Hash_Map.remove(Object key)

Parameters: The method takes one parameter key whose mapping is to be removed from the Map.

Return Value: The method returns the value that was previously mapped to the specified key if the key exists else the method returns NULL.

Below programs illustrates the working of java.util.WeakHashMap.remove() method:
Program 1: When passing an existing key.

// Java code to illustrate the remove() method 
import java.util.*; 
  
public class Weak_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty WeakHashMap 
        Map<Integer, String> weak_hash = new 
                       WeakHashMap<Integer, String>(); 
    
        // Mapping string values to int keys 
        weak_hash.put(10, "Geeks"); 
        weak_hash.put(15, "4"); 
        weak_hash.put(20, "Geeks"); 
        weak_hash.put(25, "Welcomes"); 
        weak_hash.put(30, "You"); 
  
        // Displaying the WeakHashMap 
        System.out.println("Initial Mappings are: " +  
                                           weak_hash); 
  
        // Removing the existing key mapping 
        String returned_value =  
                         (String)weak_hash.remove(20); 
  
        // Verifying the returned value 
        System.out.println("Returned value is: " +  
                                      returned_value); 
  
        // Displayin the new map 
        System.out.println("New map is: " + weak_hash); 
    } 
} 

Output:

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
Returned value is: Geeks
New map is: {30=You, 15=4, 10=Geeks, 25=Welcomes}

Program 2: When passing a new key.

// Java code to illustrate the remove() method 
import java.util.*; 
  
public class Weak_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty WeakHashMap 
        Map<Integer, String> weak_hash =  
                   new WeakHashMap<Integer, String>(); 
  
        // Mapping string values to int keys 
        weak_hash.put(10, "Geeks"); 
        weak_hash.put(15, "4"); 
        weak_hash.put(20, "Geeks"); 
        weak_hash.put(25, "Welcomes"); 
        weak_hash.put(30, "You"); 
  
        // Displaying the WeakHashMap 
        System.out.println("Initial Mappings are: " +  
                                          weak_hash); 
  
        // Removing the new key mapping 
        String returned_value =  
                        (String)weak_hash.remove(50); 
  
        // Verifying the returned value 
        System.out.println("Returned value is: " +  
                                    returned_value); 
  
        // Displayin the new map 
        System.out.println("New map is: "+weak_hash); 
    } 
} 

Output:

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
Returned value is: null
New map is: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}

Note: The same operation can be performed with any type of Mappings with variation and combination of different data types.