/*************************************************************************
 *  Compilation:  javac BinaryConverter.java
 *  Execution:    java BinaryConverter
 *  
 *  Converts an integer to and from its binary representation.
 *
 *************************************************************************/

public class BinaryConverter { 

    // convert a String of 0's and 1's into an integer
    public static int fromBinaryString(String s) {
       int result = 0;
       for (int i = 0; i < s.length(); i++) {
          char c = s.charAt(i);
          if      (c == '0') result = 2 * result;
          else if (c == '1') result = 2 * result + 1;
       }
       return result;
    }

    // convert an int into a  String of 0's and 1's
    public static String toBinaryString(int n) {
       // special case
       if (n == 0) return "0";

       // build string from right to left
       String s = "";
       while (n > 0) {
          if (n % 2 == 0) s = '0' + s;
          else            s = '1' + s;
          n = n / 2;
       }
       return s;
    }


    public static void main(String[] args) {
        int n = 47;
        String s = "101111";
        System.out.println(n +  ":  " + toBinaryString(n));
        System.out.println(s +  ":  " + fromBinaryString(s));
    }
}