Bit Counting

Bit.java

import java.util.*;

class Bit {
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    int num = in.nextInt();
    System.out.println("Bit representation: " + printBits(num));
    System.out.println("Number of 1s: " + countBits(num));
  }

  static int countBits(int num) {
    int count = 0;

    while(num != 0) {
      if((num & 1) != 0) {
        count++;
      }
      num = num >> 1;
    }

    return count;
  }

  static String printBits(int num) {
    String bits = "";

    if(num == 0) {
      return "0";
    }

    while(num != 0) {
      if((num & 1) != 0) {
        bits = "1" + bits;
      } else {
        bits = "0" + bits;
      }
      num = num >> 1;
    }

    return bits;
  }
}