WeakHashMap containsValue() Method in Java

Last Updated : 19 Jul, 2018

The java.util.WeakHashMap.containsValue() method is used to check whether a particular value is being mapped by a single or more than one key in the WeakHashMap. It takes the Value as a parameter and returns True if that value is mapped by any of the key in the map. Syntax:

Weak_Hash_Map.containsValue(Object Value)

Parameters: The method takes just one parameter Value of Object type and refers to the value whose mapping is supposed to be checked by any key inside the map. Return Value: The method returns boolean true if the mapping of the value is detected else false. Below programs illustrate the java.util.WeakHashMap.containsValue() Method: Program 1: Mapping String Values to Integer Keys.

Java

// Java code to illustrate the containsValue() 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);

        // Checking for the Value 'Geeks'
        System.out.println("Is the value 'Geeks' present? " + 
                                     weak_hash.containsValue("Geeks"));

        // Checking for the Value 'World'
        System.out.println("Is the value 'World' present? " + 
                                      weak_hash.containsValue("World"));
    }
}

Output:

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
Is the value 'Geeks' present? true
Is the value 'World' present? false

Program 2: Mapping Integer Values to String Keys.

Java

// Java code to illustrate the containsValue() 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);

        // Checking for the Value '10'
        System.out.println("Is the value '10' present? " +
                                    weak_hash.containsValue(10));

        // Checking for the Value '30'
        System.out.println("Is the value '30' present? " + 
                                    weak_hash.containsValue(30));

        // Checking for the Value '40'
        System.out.println("Is the value '40' present? " +
                                    weak_hash.containsValue(40));
    }
}

Output:

Initial Mappings are: {Welcomes=25, 4=15, You=30, Geeks=20}
Is the value '10' present? false
Is the value '30' present? true
Is the value '40' present? false

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

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