//Title of this code

//'main' method must be in a class 'Rextester'.

//Compiler version 1.8.0_45

//1, 5, 7, 54, 62, 2, 1, 54, 24, 1

​

import java.util.*;

import java.lang.*;

​

class Rextester

{  

    public static void main(String args[])

    {

        int[] numbers = {1, 5, 7, 54, 62, 2, 1, 54, 24, 1};

        Set<Integer> set = new HashSet<Integer>();

        for (int n : numbers)

        {

            boolean unique = set.add(n);

            if (!unique)            //(!unique == false)

            System.out.println("Duplicate: " + n);

        }

    }

}