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WeakHashMap clear() Method in Java

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  • Last Updated : 19 Jul, 2018
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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, "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);
  
        // 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=Geeks, 25=Welcomes, 20=Geeks}
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("Geeks", 10);
        weak_hash.put("4", 15);
        weak_hash.put("Geeks", 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, Geeks=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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