public static void start(String group) {
   if (timers.containsKey(group)) {
     timers.clear();
     throw new IllegalArgumentException(
         MessageUtil.getMessage("message.timerAlreadyStarted", group));
   }
   timers.put(group, System.currentTimeMillis());
 }
  public static void end(String group) {
    Long end = timers.get(group);
    if (end == null) {
      timers.clear();
      throw new IllegalArgumentException(
          MessageUtil.getMessage("message.timerNeverStarted", group));
    }
    timers.remove(group);

    log.info("[" + group + "] Time: " + (System.currentTimeMillis() - end));
  }