WeakHashMap clear() Method in Java

The java.util.WeakHashMap.clear() method in Java is used to clear and remove all of the elements or mappings from a specified map.

Syntax:

Weak_Hash_Map.clear()

Parameters: The method does not accept any parameters.

Return Value: The method does not return any value.

Below programs are used to illustrate the working of java.util.WeakHashMap.clear() Method:

Program 1: Mapping String Values to Integer Keys.

// Java code to illustrate the clear() 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, "Beginner"); 
        weak_hash.put(15, "4"); 
        weak_hash.put(20, "Beginner"); 
        weak_hash.put(25, "Welcomes"); 
        weak_hash.put(30, "You"); 
  
        // Displaying the WeakHashMap 
        System.out.println("Initial Mappings are: "
                           + weak_hash); 
  
        // Clearing the map using clear() 
        weak_hash.clear(); 
  
        // Displaying the final WeakHashMap 
        System.out.println("Final Map: "
                           + weak_hash); 
    } 
} 

Output:

Initial Mappings are: {30=You, 15=4, 10=Beginner, 25=Welcomes, 20=Beginner}
Final Map: {}

Program 2: Mapping Integer Values to String Keys.

// Java code to illustrate the clear() method 
import java.util.*; 
  
public class Weak_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty WeakHashMap 
        Map<String, Integer> weak_hash = new WeakHashMap<String, Integer>(); 
  
        // Mapping int values to string keys 
        weak_hash.put("Beginner", 10); 
        weak_hash.put("4", 15); 
        weak_hash.put("Beginner", 20); 
        weak_hash.put("Welcomes", 25); 
        weak_hash.put("You", 30); 
  
        // Displaying the WeakHashMap 
        System.out.println("Initial Mappings are: " + weak_hash); 
  
        // Clearing the map using clear() 
        weak_hash.clear(); 
  
        // Displaying the final WeakHashMap 
        System.out.println("Final Map: "
                           + weak_hash); 
    } 
} 

Output:

Initial Mappings are: {Welcomes=25, 4=15, You=30, Beginner=20}
Final Map: {}

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

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