我正在尝试使用ScheduledExecutorService每15分钟调用一次可运行任务。任务应在以下时间每小时运行一次: 2分10秒 17分10秒 32分10秒 47分10秒。

我使用Calendar实例计算第一次执行任务的初始延迟,然后使用scheduleAtFixedRate()的延迟,每15分钟执行一次任务。这在头几天很好,但几天后,我可以观察到任务执行过程中的一些时间变化。例如,本应在12:02:10开始的任务在12:03:45被调用。我这是哪里出错了?

public static void main(String[] args) {    
  final ScheduledExecutorService scheduler = Executors
                .newScheduledThreadPool(15);
  Date aDate = new Date();
  Calendar cal = Calendar.getInstance();
  cal.setTime(aDate);
  int currentHour = cal.get(Calendar.HOUR_OF_DAY);
  int currentMins = cal.get(Calendar.MINUTE);
  int currentSecs = cal.get(Calendar.SECOND);
  int unitInSecs;      
  int delayFor15MinTasksInSecs;
  unitInSecs = currentMins * 60 + currentSecs;
  delayFor15MinTasksInSecs = unitInSecs < (3 * 60 - 50 ) ? (3 * 60 - 50 ) - unitInSecs : unitInSecs < (18 * 60 - 50 ) ? (18 * 60 - 50 ) - unitInSecs : unitInSecs < (33 * 60 - 50 ) ? (33 * 60 - 50 ) - unitInSecs : unitInSecs < (48 * 60 - 50 )? (48 * 60 - 50 ) - unitInSecs : (63 *60 - 50 ) - unitInSecs;
  scheduler.scheduleAtFixedRate(new RTPAcquiringTask(10), delayFor15MinTasksInSecs, 15*60, TimeUnit.SECONDS);
}