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 llustrate the java.util.Map.entrySet() Method:



Program 1: Mapping String Values to Integer Keys.

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// 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());
    }
}

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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.











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// 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()); 


    } 


} 



















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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()


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