Map entrySet() method in Java with Examples

The java.util.Map.entrySet() method in Java is used to create a set out of the same elements contained in the map. It basically returns a set view of the map or we can create a new set and store the map elements into them.

Syntax:

map.entrySet()

Parameters: The method does not take any parameter.

Return Value: The method returns a set having same elements as the hash map.

Below programs illustrate the java.util.Map.entrySet() Method:

Program 1: Mapping String Values to Integer Keys.

// Java code to illustrate the entrySet() method

import java.util.*;

public class Map_Demo {
    public static void main(String[] args)
    {
        // Creating an empty Map
        Map<Integer, String> map = new HashMap<Integer, String>();

        // Mapping string values to int keys
        map.put(10, "Geeks");
        map.put(15, "4");
        map.put(20, "Geeks");
        map.put(25, "Welcomes");
        map.put(30, "You");

        // Displaying the Map
        System.out.println("Initial Mappings are: " + map);

        // Using entrySet() to get the set view
        System.out.println("The set is: " + map.entrySet());
    }
}

Output:

Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
The set is: [20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4]

Program 2: Mapping Integer Values to String Keys.

// Java code to illustrate the entrySet() method
import java.util.*;

public class Map_Demo {
    public static void main(String[] args)
    {
        // Creating an empty Map
        Map<String, Integer> map = new HashMap<String, Integer>();

        // Mapping int values to string keys
        map.put("Geeks", 10);
        map.put("4", 15);
        map.put("Geeks", 20);
        map.put("Welcomes", 25);
        map.put("You", 30);

        // Displaying the Map
        System.out.println("Initial Mappings are: " + map);

        // Using entrySet() to get the set view
        System.out.println("The set is: " + map.entrySet());
    }
}

Output:

Initial Mappings are: {4=15, Geeks=20, You=30, Welcomes=25}
The set is: [4=15, Geeks=20, You=30, Welcomes=25]

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

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/Map.html#entrySet()