code: public static boolean isNumeric(String s)
      {
          boolean ret = true;
          for(int i = 0; i < s.length() && ret; i++)
          {
              char c = s.charAt(i);
              ret = (c >= '0' && c <= '9');
          }
          return ret;
      }
docs: Returns <CODE>true</CODE> if the the given string contains only numeric digits [0-9].
  @param s The string to be checked
  @return <CODE>true</CODE> if the the given string contains only numeric digits [0-9]