Main.java

import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;

public class Main {

    public static void main(String[] args) {
	// write your code here
        int[] nums = new int[]{801, 7317, 3946, 240, 9935, 4293, 7260, 3414, 1533, 786, 6297, 3946, 4355, 2535, 4919};

        sort(nums);
        System.out.println(findDuplicateNumber(nums));
    }

    private static int findDuplicateNumber(int[] nums) {
        long time = System.nanoTime();
        long end;

        nums = sort(nums);

        for (int i = 0; i < nums.length - 1; i++) {
            if (nums[i] == nums[i + 1]) {
                end = System.nanoTime();
                System.out.println("Found duplicate in " + (end - time) + " nanoseconds");
                return nums[i];
            }
            ;
        }

        end = System.nanoTime();
        System.out.println("There was not a duplicate! Found in " + (end - time) + " nanoseconds");
        return -1; // No duplicate
    }

    private static boolean sorted(final int[] nums) {
        for (int i = 0; i < nums.length - 1; i++) {
            if (nums[i] > nums[i + 1]) return false;
        }
        return true;
    }


    private static int[] sort(final int[] nums) {
        long time = System.nanoTime();
        boolean sorted = false;

        if (sorted(nums)) return nums;

        while (!sorted) {
            sorted = sorted(nums);
            for (int i = 0; i < nums.length - 1; i++) {
                if (nums[i] > nums[i + 1]) {
                    int temp = nums[i];
                    int tempB = nums[i + 1];

                    nums[i] = tempB;
                    nums[i + 1] = temp;
                }
            }
        }

        long endTime = System.nanoTime() - time;
        System.out.println("Sorted in " + endTime + " nanoseconds");

        return nums;
    }
}