Java Integer.toBinaryString()

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int a = sc.nextInt();
        char[] chars = Integer.toBinaryString(a).toCharArray();
        int num = 0;
        for(char c : chars) {
            if(c == '1') num++;
        }
        System.out.print(num);
    }
}