Basics In Java

import java.io.*;
class BtoD
 {
   public static  void main()throws IOException
     {
         DataInputStream k=new DataInputStream(System.in);
         System.out.println("enter a number");
         n=Integer.parseInt(k.readLine());
         int r;double s=0,i=0;
         while(n>0)
         {
             r=n%10;
             s=s+r*Math.pow(2,i);
             n=n/10;
             i++;
          }
            System.out.println(s);
        }
    }
-----------------------OUTPUT----------------------------------
Enter number-:10
2