ConcurrentHashMap entrySet() method in Java with Examples

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

Syntax:

ConcurrentHashMap.entrySet()

Parameters: The method does not take any parameter.

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

Below programs are used to illustrate the working of entrySet() Method:

Program 1: Mapping String Values to Integer Keys.

// Java code to illustrate the entrySet() method 
  
import java.util.*; 
import java.util.concurrent.*; 
  
public class ConcurrentHashMapDemo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty ConcurrentHashMap 
        ConcurrentHashMap<Integer, String> 
            hash_map = new ConcurrentHashMap<Integer, String>(); 
  
        // Mapping string values to int keys 
        hash_map.put(10, "Geeks"); 
        hash_map.put(15, "4"); 
        hash_map.put(20, "Geeks"); 
        hash_map.put(25, "Welcomes"); 
        hash_map.put(30, "You"); 
  
        // Displaying the HashMap 
        System.out.println("Initial Mappings are: " + hash_map); 
  
        // Using entrySet() to get the set view 
        System.out.println("The set is: " + hash_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.*; 
import java.util.concurrent.*; 
  
public class ConcurrentHashMapDemo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty ConcurrentHashMap 
        ConcurrentHashMap<String, Integer> 
            hash_map = new ConcurrentHashMap<String, Integer>(); 
  
        // Mapping int values to string keys 
        hash_map.put("Geeks", 10); 
        hash_map.put("4", 15); 
        hash_map.put("Geeks", 20); 
        hash_map.put("Welcomes", 25); 
        hash_map.put("You", 30); 
  
        // Displaying the HashMap 
        System.out.println("Initial Mappings are: " + hash_map); 
  
        // Using entrySet() to get the set viewa 
        System.out.println("The set is: " + hash_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.

Attention reader! Don’t stop learning now. Get hold of all the important Java and Collections concepts with the Fundamentals of Java and Java Collections Course at a student-friendly price and become industry ready.

My Personal Notes

Recommended Posts: