code: private void parameterizedLog(final String level,
                                  final Object parameterizedMsg,
                                  final Object param1,
                                  final Object param2) {
      if (parameterizedMsg instanceof String) {
        String msgStr = (String) parameterizedMsg;
        msgStr = MessageFormatter.format(msgStr, param1, param2);
        log(level, msgStr, null);
      } else {
        // To be failsafe, we handle the case where 'messagePattern' is not
        // a String. Unless the user makes a mistake, this should not happen.
        log(level, parameterizedMsg.toString(), null);
      }
    }
docs: For parameterized messages, first substitute parameters and then log.
  
  @param level level
  @param parameterizedMsg message pattern
  @param param1 param1
  @param param2 param2