Write a Java program to find duplicate elements in an array

for explanation watch video

Find Duplicates using HashSet

import java.util.HashSet;

public class FindDuplicates {
    public static void main(String[] args) {
        int[] array = {1, 2, 3, 4, 5, 2, 6, 4, 7, 8, 3};

        findDuplicates(array);
    }

    public static void findDuplicates(int[] array) {
        HashSet<Integer> set = new HashSet<>();
        HashSet<Integer> duplicates = new HashSet<>();

        for (int num : array) {
            if (!set.add(num)) { // if add() returns false, num is a duplicate
                duplicates.add(num);
            }
        }

        if (duplicates.isEmpty()) {
            System.out.println("No duplicates found");
        } else {
            System.out.println("Duplicate elements: " + duplicates);
        }
    }
}

Using For loop

public class FindDuplicatesUsingLoop {
    public static void main(String[] args) {
        int[] array = {1, 2, 3, 4, 5, 2, 6, 4, 7, 8, 3};

        findDuplicates(array);
    }

    public static void findDuplicates(int[] array) {
        boolean hasDuplicates = false;

        System.out.print("Duplicate elements: ");
        for (int i = 0; i < array.length; i++) {
            for (int j = i + 1; j < array.length; j++) {
                if (array[i] == array[j]) {
                    System.out.print(array[i] + " ");
                    hasDuplicates = true;
                    break; // Avoids printing the same duplicate multiple times
                }
            }
        }

        if (!hasDuplicates) {
            System.out.print("No duplicates found");
        }
    }
}