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ConcurrentHashMap entrySet() method in Java with Examples

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  • Last Updated : 30 Oct, 2018
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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.


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