如何停止ScheduledExecutorService？ [英] How to stop a ScheduledExecutorService?

问题描述

程序在九次打印后完成：

The program finishes after nine prints:

class BeeperControl {

    private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);

    public void beep() {
        final Runnable beeper = new Runnable() {
            public void run() {
                System.out.println("beep");
            }
        };
        final ScheduledFuture<?> beeperHandle = scheduler.scheduleAtFixedRate(
                beeper, 1, 1, SECONDS);
        scheduler.schedule(new Runnable() {
            public void run() {
                beeperHandle.cancel(true);
            }
        }, 1 * 9, SECONDS);
    }

    public static void main(String[] args) {
        BeeperControl bc = new BeeperControl();
        bc.beep();
    }
}

如何停止进程（即eclipse中的java进程）例如）因为它在9秒内没有停止时间？

How to stop a process (i.e. java process in eclipse for example) because it does not stop after a time limit in 9 seconds?

推荐答案

你遇到的问题是调度程序保持不变取消蜂鸣声任务后的实时线程。

The issue you have is that the scheduler keeps a live thread around after you have cancelled the beep task.

如果有一个实时非守护程序线程，则JVM保持活动状态。

If there is a live non-daemon thread, the JVM stays alive.

它保留这个线程的原因是你告诉它在这一行中这样做：

The reason that it keeps this thread around is that you have told it to do so in this line:

private final ScheduledExecutorService scheduler
        = Executors.newScheduledThreadPool(1);

请注意 newScheduledThreadPool（int corePoolSize）：

corePoolSize - 要保留在池中的线​​程数，甚至如果他们闲着。

corePoolSize - the number of threads to keep in the pool, even if they are idle.

那么，你有两种方法可以让JVM终止：

So, you have two possible ways to cause the JVM to terminate:

1. 将 0 传递给 newScheduledThreadPool 而不是1 。调度程序不会保留活动线程，JVM将终止。

1. Pass 0 to newScheduledThreadPool instead of 1. The scheduler will not keep a live thread, and the JVM will terminate.

关闭调度程序。无论如何，您应该这样做以释放其资源。因此，将匿名 Runnable 中的运行更改为：

Shut down the scheduler. You are supposed to do so anyway to release its resources. So change the run in your anonymous Runnable to:

public void run() {
    beeperHandle.cancel(true);
    scheduler.shutdown();
}

（事实上，那里不需要取消 - shutdown 将在下一次嘟嘟完成后立即生效。）

(In fact, you don't need the cancel there - the shutdown will take effect as soon as the next "beep" is completed.)

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