docs: synchronized public static void start(boolean isDeamon) {
  		if (null == crontabSetting) {
  			// 尝试查找config/cron.setting
  			setCronSetting(CRONTAB_CONFIG_PATH);
  		}
  		// 尝试查找cron.setting
  		if (null == crontabSetting) {
  			setCronSetting(CRONTAB_CONFIG_PATH2);
  		}
  		if (scheduler.isStarted()) {
  			throw new UtilException("Scheduler has been started, please stop it first!");
  		}
  
  		schedule(crontabSetting);
  		scheduler.start(isDeamon);
  	}