Map entrySet() method in Java with Examples (original) (raw)

Last Updated : 20 Jan, 2022

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 `

// 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 `

// 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()