What is the Hashtable.entrySet method in Java?

A hash table is a collection of key-value pairs.

In Java, the Hashtableclass includes the entrySet method, which gets all the entrieskey-value mappings of the Hashtable object as a Set view.

Any changes made to the hash table will be reflected in the Set view as well.

Syntax

public Set<Map.Entry<K,V>> entrySet()

Parameters

This method doesn’t take any parameters.

Return value

The entrySet method returns a Set view of all of the entries on the Hashtable object.

Code

The example below shows how to use the entrySet method.

import java.util.Hashtable;
import java.util.Set;
import java.util.Map;
class EntrySetExample {
    public static void main( String args[] ) {
        Hashtable<Integer, String> map = new Hashtable<>();
        map.put(1, "one");
        map.put(2, "two");
        
        System.out.println("The map is -" + map );
        Set<Map.Entry<Integer, String>> entries = map.entrySet();
        System.out.println("The entries are -" +   entries);
        System.out.println("\nAdding a new entry 4 - four to the map" );
        map.put(4, "four");
        System.out.println("After adding the entries are -" + entries);
    }
}

Explanation

In the code above:

In line 1, we import the Hashtable class.
In line 7, we create a Hashtable object with the name map.
In lines 8 and 9, we use the put method to add two mappings ({1=one, 2=two}) to the map object.
In line 13, we get the map object entries with the entrySet method and store them in the entries variable.
In line 17, we add a new entry 4 - "four" to the map.
In line 19, we print the entries object. The newly added entry, 4 - "four" will be automatically available in the entries variable without the need to call the entrySet method because the entrySet method returns the set view.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)