HashSet Class:

It extends AbstractList class and implements List interface. It uses hashing technique to store data. It contains only unique elements. We can use HashSet class by importing java.util package.

Example:

import java.util.*;

public class HashDemo {

   public static void main(String args[]) {
      // create a hash set 
      HashSet hash = new HashSet();
      // add elements to the hash set using add() function
      hash.add("B");
      hash.add("A");
      hash.add("D");
      hash.add("E");
      hash.add("C");
      hash.add("F");
      System.out.println(hash); //printing the hash collection
   }
}

Output:

[A, B, C, D, E, F]

List can have duplicate elements but Set contains unique elements only.

Some of the mostly used methods of HashSet :

add(): used to add a element to the set

clear(): Removes all element from the set.

remove() :Removes the specified element from the set if it is present.