Open In App

WeakHashMap containsKey() Method in Java

Last Updated : 19 Jul, 2018
Improve
Improve
Like Article
Like
Save
Share
Report

The java.util.WeakHashMap.containsKey() method is used to check whether a particular key is being mapped into the WeakHashMap or not. It takes the key element as a parameter and returns True if that element is mapped in the map.

Syntax:

Weak_Hash_Map.containsKey(key_element)

Parameters: The method takes just one parameter key_element that refers to the key whose mapping is supposed to be checked inside a map.

Return Value: The method returns boolean true if the presence of the key is detected else false .

Below programs are used to illustrate the working of java.util.WeakHashMap.containsKey() Method:
Program 1: Mapping String Values to Integer Keys.




// Java code to illustrate the containsKey() 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 key_element '20'
        System.out.println("Is the key '20' present? "
                                  weak_hash.containsKey(20));
  
        // Checking for the key_element '5'
        System.out.println("Is the key '5' present? "
                                   weak_hash.containsKey(5));
    }
}


Output:

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
Is the key '20' present? true
Is the key '5' present? false

Program 2: Mapping Integer Values to String Keys.




// Java code to illustrate the containsKey() 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 key_element 'Welcomes'
        System.out.println("Is the key 'Welcomes' present? "
                                  weak_hash.containsKey("Welcomes"));
  
        // Checking for the key_element 'World'
        System.out.println("Is the key 'World' present? "
                                      weak_hash.containsKey("World"));
    }
}


Output:

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

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



Like Article
Suggest improvement
Previous
Next
Share your thoughts in the comments

Similar Reads