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Java HashMap keySet() Method with Example

HashMap Class keySet() method: Here, we are going to learn about the keySet() method of HashMap Class with its syntax and example.
Submitted by Preeti Jain, on March 04, 2020

HashMap Class keySet() method

• keySet() method is available in java.util package.
• keySet() method is used to return a set of keys exist in this HashMap 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 returning the key 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 all keys exist in this HashMap to be viewed in a Set.

Example:

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

import java.util.*;

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

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

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

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

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

Output

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