带有时间限制的Runnable [英] Runnable with a time limit

问题描述

尝试构建一个 Runnable 必须在给定的时间限制内结束。

目前我正在使用 java.util.Timer 来中断 Runnable 线程。

计时器在 Runnable 启动后立即启动。

  import java.util.Timer; 
 import java.util.TimerTask; 
 
公共类测试{
线程任务; 
定时器计时器; 
 
 public void start（）{
 
 task = new Thread（new worker（））; 
 timer = new Timer（timer，true）; 
 
 task.start（）; 
 timer.schedule（new Terminator（），1000 * 2）; 
} 
 
 
类工人实现Runnable {
 @覆盖
公共无效的run（）{
 
为（INT I = 0; i< 2; i ++）{
 try {
 Thread.sleep（1000）; 
} catch（InterruptedException e）{
 System.out.println（Test Interrupted !!）; 
返回; 
} 
} 
 
 System.out.println（Test Finished !!）; 
 timer.cancel（）; 
} 
} 
 
类终结者延伸的TimerTask {
 @覆盖
公共无效的run（）{
 task.interrupt（）; 
 System.out.println（Test Terminated !!）; 
} 
} 
} 
  

但我怀疑这导致计时器和 Runnable 线程之间的竞争条件：
Runnable 即将完成，计时器也在解雇。

这是否会导致完成!! 和终止!! 正在打印？如果是这样，人们如何避免它？

更新：

它发生：

  11-09 21：14：40.741：INFO / System.out（31442）：测试结束!! 18 
 11-09 21：14：40.751：INFO / System.out（31442）：测试终止!! 18 
 11-09 21：14：40.751：INFO / System.out（31442）：测试结束!! 19 
 11-09 21：14：40.751：INFO / System.out（31442）：测试终止!! 19 
  

解决方案

CAN这个不断结果两个完成!!并终止!!被打印？

是的。打印消息已完成时，计时器可能会在取消之前触发。

  System.out.println（ 完成!!）; 
 //计时器可以在这里开火。 
 timer.cancel（）; 
  

如果发生这种情况，将打印这两条消息。

---

为避免此问题，您可以使用同步。

  synchronized（ someObject）{
 if（！finished）{
 finished = true; 
 System.out.println（Finished !!）; 
 timer.cancel（）; 
} 
} 
  

在终止符中：

  synchronized（someObject）{
 if（！finished）{
 finished = true; 
 task.interrupt（）; 
 System.out.println（Test Terminated !!）; 
} 
} 
  

这可以防止打印两个邮件。

Trying to construct a Runnable that must end within a given time limit.

Currently I'm using java.util.Timer to interrupt Runnable thread.

Timer starts right after Runnable starts.

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

public class test {
    Thread task;
    Timer  timer;

    public void start(){

        task = new Thread(new worker());
        timer = new Timer("timer",true);

        task.start();
        timer.schedule(new Terminator(),1000*2);
    }


    class worker implements Runnable{
        @Override
        public void run() {

            for (int i = 0 ; i < 2; i++){
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    System.out.println("Test Interrupted !!");
                    return;
                }
            }

            System.out.println("Test Finished !!");
            timer.cancel();
        }
    }

    class Terminator extends TimerTask{
        @Override
        public void run() {
            task.interrupt();
            System.out.println("Test Terminated !!");
        }
    }
}

But I suspect this results in a race condition between Timer and Runnable threads: Runnable is about to complete, and Timer is also firing.

Can this ever result in both Finished !! and Terminated !! being printed ? If so, how one avoids it ?

Update:

It happens:

11-09 21:14:40.741: INFO/System.out(31442): Test Finished !! 18
11-09 21:14:40.751: INFO/System.out(31442): Test Terminated !! 18
11-09 21:14:40.751: INFO/System.out(31442): Test Finished !! 19
11-09 21:14:40.751: INFO/System.out(31442): Test Terminated !! 19

解决方案

Can this ever result in both Finished !! and Terminated !! being printed ?

Yes. When the message "finished" is printed it's possible that the timer will fire before it is cancelled.

System.out.println("Finished !!");
// The timer can fire here.
timer.cancel(); 

If this happens, both messages will be printed.

---

To avoid the problem you can use synchronization.

synchronized (someObject) {
    if (!finished) {
        finished = true;
        System.out.println("Finished !!");
        timer.cancel(); 
    }
}

And in the terminator:

synchronized (someObject) {
    if (!finished) {
        finished = true;
        task.interrupt();
        System.out.println("Test Terminated !!");
    }
}

This prevents both messages form being printed.

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