find duplicate items in array

 Find duplicate items in array in java

This is the java program to find the duplicate elements inside an array.

package com.javadevelopersnotes.controller;

import java.util.HashSet;
import java.util.Set;

public class FindDuplicates {

    public static void main(String[] args) {
        int arr[] = {1, 2, 3, 4, 5, 5, 6, 7, 8, 8, 9};
        int n = arr.length;

        Set<Integer> uniqueNumbers = new HashSet<>();
        Set<Integer> duplicateNumbers = new HashSet<>();

        for (int num : arr) {
            if (uniqueNumbers.add(num) == false) {
                duplicateNumbers.add(num);
            }
        }

        System.out.println("Below are the unique items");

        for (int item : uniqueNumbers) {
            System.out.println(item);
        }

        System.out.println("Below are the duplicate items");

        for (int item : duplicateNumbers) {
            System.out.println(item);
        }

    }
}