Find duplicate element in array

Find a duplicate element in the given array of integers. There will be only a single duplicate element in the array.
Note: Do not use any inbuilt functions/libraries for your main logic.

Input Format

First line of input contains size of the array – N and second line contains the elements of the array.

Constraints

2 <= N <= 100
0 <= ar[i] <= 10⁹

Output Format

Print the duplicate element from the given array.

Input	Output
6 5 4 10 9 21 10	10

import java.util.Scanner;
public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] arr = new int[N];
        for (int j = 0; j < N; j++) {
            arr[j] = sc.nextInt();
        }
        sorting(arr);
        int duplicate = Duplicates(arr);
        System.out.println(duplicate);
    }
    public static void sorting(int[] arr) {
        int n = arr.length;
        for (int i = 0; i < n - 1; i++) {
            int minInd = i;
            for (int j = i + 1; j < n; j++) {
                if (arr[j] < arr[minInd]) {
                    minInd = j;
                }
            }
            if (minInd != i) {
                int temp = arr[i];
                arr[i] = arr[minInd];
                arr[minInd] = temp;
            }
        }
    }
    private static int Duplicates(int[] arr) {
        int n = arr.length;
        for (int i = 0; i < n - 1; i++) {
            if (arr[i] == arr[i + 1]) {
                return arr[i];
            }
        }
        return -1;
    }
}