Java Program to Demonstrate HashSet

import java.util.HashSet;

public class HashSetExample {
    public static void main(String[] args) {
        HashSet<Integer> numbers = new HashSet<>();

        // Add elements
        numbers.add(2);
        numbers.add(5);
        numbers.add(6);
        System.out.println("HashSet: " + numbers);

        // Add duplicate element
        boolean isAdded = numbers.add(5);
        System.out.println("Is 5 added? " + isAdded);
        System.out.println("HashSet after adding duplicate: " + numbers);
    }
}

HashSet: [2, 5, 6]
Is 5 added? false
HashSet after adding duplicate: [2, 5, 6]