code: private long getJobFireInterval(){
      	if(jobFireInterval == 0){   
      		try {				
      			Date nextFireTime = getTrigger().getNextFireTime();
      			Date previousFireTime = getTrigger().getPreviousFireTime();
      			jobFireInterval = nextFireTime.getTime() - previousFireTime.getTime();
  			} catch (Exception e) {}
      	}
      	return jobFireInterval;
      }
docs: 获取任务执行间隔
  @return
  @throws SchedulerException