code: private static void padInt(StringBuilder buffer, int value, int length) {
          String strValue = Integer.toString(value);
          for (int i = length - strValue.length(); i > 0; i--) {
              buffer.append('0');
          }
          buffer.append(strValue);
      }
docs: Zero pad a number to a specified length
  
  @param buffer buffer to use for padding
  @param value the integer value to pad if necessary.
  @param length the length of the string we should zero pad