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Java WeakHashMap keySet() Method with Example

WeakHashMap Class keySet() method: Here, we are going to learn about the keySet() method of WeakHashMap Class with its syntax and example.
Submitted by Preeti Jain, on February 23, 2020

WeakHashMap Class keySet() method

• keySet() method is available in java.util package.
• keySet() method is used to retrieve all the key exists in this map to be viewed in a set.
• keySet() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.
• keySet() method does not throw an exception at the time of viewing elements in a set.

Syntax:

    public Set keySet();

Parameter(s):

• It does not accept any parameter.

Return value:

The return type of the method is Set, it returns existing keys in this map to be viewed in a set.

Example:

// Java program to demonstrate the example 
// of Set keySet() method of WeakHashMap 

import java.util.*;

public class KeySetOfWeakHashMap {
    public static void main(String[] args) {
        // Instantiates a WeakHashMap object
        Map < Integer, String > map = new WeakHashMap < Integer, String > ();

        // By using put() method is to add
        // key-value pairs in a WeakHashMap
        map.put(10, "C");
        map.put(20, "C++");
        map.put(50, "JAVA");
        map.put(40, "PHP");
        map.put(30, "SFDC");

        // Display WeakHashMap
        System.out.println("WeakHashMap: " + map);

        // By using keySet() method is to
        // return the set of of keys exists
        // in this WeakHashMap to be viewed in a Set
        Set s = map.keySet();

        // Display status
        System.out.print("map.keySet(): ");
        System.out.println(s);
    }
}

Output

WeakHashMap: {30=SFDC, 40=PHP, 10=C, 20=C++, 50=JAVA}
map.keySet(): [30, 40, 10, 20, 50]