code: public static String getMessage(final int code, int subCode,
                                      final Object[] add) {
  
          String message = getResourceString(code);
  
          if (subCode != 0) {
              message += getResourceString(subCode);
          }
  
          if (add != null) {
              message = insertStrings(message, add);
          }
  
          return message;
      }
docs: Returns the error message given the error code.<br/> This method is used
  when throwing exception other than <code>HsqlException</code>.
  
  @param code the code for the error message
  @param subCode the code for the addon message
  @param add value(s) to use to replace the placeholer(s)
  @return the error message associated with the error code