java定时器任务调度 [英] java timer task schedule

问题描述

从 Stack Overflow 上的阅读来看，我看到你们中的许多人不推荐使用 Timer Task.嗯...但我已经实现了这个:

From reading on Stack Overflow I've seen that many of you don't recommend using Timer Task. Hmmm... but I already implemented this:

我有这个代码:

detectionHandlerTimer.schedule(myTimerTask, 60 * 1000, 60 * 1000);

问题是 myTimerTask 的工作会持续一段时间.

The thing is that work of myTimerTask lasts some time.

我想要这种行为:

1. 等待 60 秒.
2. 完成一段时间的任务(例如 40 - 100 秒).
3. 任务完成.
4. 等待 60 秒.
5. 完成一段时间的任务(例如 40 - 100 秒).

但是上面的代码是这样的

But the code above behaves like this

1. 等待 60 秒.
2. 完成一段时间的任务(例如 40 - 100 秒).
3. 任务完成
4. 完成一段时间的任务(例如 40 - 100 秒).

由于任务的持续时间大于60，定时器在任务完成后立即启动任务.但我希望它再等一次.

Because the time duration of task is bigger than 60, timer starts task immediately after task is finished. But I would like it to wait again.

推荐答案

这有效.关键是让任务本身(完成后)安排任务的下一次发生.

This works. The key is to have the task itself (after it completes) schedule the next occurrence of the task.

import java.util.Timer;
import java.util.TimerTask;

public class TaskManager {

    private Timer timer = new Timer();

    public static void main(String[] args) {
        TaskManager manager = new TaskManager();
        manager.startTask();
    }

    public void startTask() {
        timer.schedule(new PeriodicTask(), 0);
    }

    private class PeriodicTask extends TimerTask {
        @Override
        public void run() {
            System.out.println(System.currentTimeMillis() + " Running");

            /* replace with the actual task */
            try {
                Thread.sleep(15 * 1000);
            } catch(InterruptedException e) {
                e.printStackTrace();
            }
            /* end task processing */

            System.out.println(System.currentTimeMillis() + " Scheduling 10 seconds from now");
            timer.schedule(new PeriodicTask(), 10 * 1000);
        }
    }
}

打印:

$ javac TaskManager.java && java TaskManager
1288282514688 Running
1288282529711 Scheduling 10 seconds from now
1288282539712 Running
1288282554713 Scheduling 10 seconds from now
1288282564714 Running

如果您提取时间戳的第二个组成部分(为了清楚起见)，则如下所示:

Here's what it looks like if you extract the second components of the timestamps (for clarity):

$ javac TaskManager.java && java TaskManager
14                                    Running
29 (+15 seconds execution)            Scheduling 10 seconds from now
39 (+10 seconds delay until next run) Running
54 (+15 seconds execution)            Scheduling 10 seconds from now
64 (+10 seconds delay until next run) Running

只需将 10 替换为 60 即可.

Just replace the 10s with 60s.

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