Count Of Bits One - Task

import java.util.Scanner;


public class CountOfbitsOne {

    public static void main(String[] args) {

        @SuppressWarnings("resource")
        Scanner input = new Scanner(System.in);

        int a = input.nextInt();
        int countBitsOne = 0;
        int mask = 1;
        String aBinaryString = String.format("%16s",Integer.toBinaryString(a)).replace(' ', '0');
        int aBinaryInteger = Integer.parseInt(aBinaryString);

        for (int i = 0; i < aBinaryString.length(); i++) {
            if (((mask << i) & aBinaryInteger) == 1) {
                countBitsOne ++;
            }
        }

        System.out.printf("%16s",aBinaryString);
        System.out.println();
        System.out.println(countBitsOne);

    }

}