A hash table is a collection of key-value pairs.
In Java, the Hashtableclass includes the entrySet method, which gets all the Hashtable object as a Set view.
Any changes made to the hash table will be reflected in the Set view as well.
public Set<Map.Entry<K,V>> entrySet()
This method doesn’t take any parameters.
The entrySet method returns a Set view of all of the entries on the Hashtable object.
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);}}
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.