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()); }} |
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()); }} |
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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