java - 更改线程池中一个线程的延迟

Question

我向我的线程池添加了三个具有不同任务和不同延迟的线程，并且一切正常。

static ScheduledExecutorService scheduleTaskExecutor;
static ScheduledFuture<?> future1;
static ScheduledFuture<?> future2;
static ScheduledFuture<?> future3;

public void onCreate(Bundle savedInstanceState) {
    scheduleTaskExecutor = Executors.newScheduledThreadPool(3);
    future1 = scheduleTaskExecutor.scheduleWithFixedDelay(new Runnable1() {...}, 0, olddelay1, TimeUnit.SECONDS); // Task 1
    future2 = scheduleTaskExecutor.scheduleWithFixedDelay(new Runnable2() {...}, 0, olddelay2, TimeUnit.SECONDS); // Task 2
    future3 = scheduleTaskExecutor.scheduleWithFixedDelay(new Runnable3() {...}, 0, olddelay3, TimeUnit.SECONDS); // Task 3
}

稍后在运行时我想更改其中一个线程的延迟(无论哪个线程)，其他线程将继续使用旧的延迟。我认为 ScheduledFuture 引用可能有所帮助并尝试了以下代码(例如第二个线程)，但执行后线程池中只剩下一个线程(任务 2)。

public void changeDelay2(int newdelay2){
    future2.cancel(true);
    future2 = scheduleTaskExecutor.scheduleWithFixedDelay(new Runnable2() {...}, 0, newdelay2, TimeUnit.SECONDS); // Task 2
}

那么有没有可能只改变一个线程的延迟呢？

Answer 1

你完全按照你所做的去做 - 你的代码中一定有其他错误。

这是一个完整的工作示例，它与您正在做的事情相同。下面的输出表明它正在按预期工作。

public class Reschedule {

    public static void main(String[] args) throws InterruptedException {
        long start = System.currentTimeMillis();
        ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();

        // Schedule three tasks
        ScheduledFuture future1 = executor.scheduleAtFixedRate(() -> {
            System.out.printf("%03ds: This is the first runnable, reporting in%n", (System.currentTimeMillis() - start) / 1000);
        }, 0, 5, TimeUnit.SECONDS);
        ScheduledFuture future2 = executor.scheduleAtFixedRate(() -> {
            System.out.printf("%03ds: This is the second runnable, reporting in%n", (System.currentTimeMillis() - start) / 1000);
        }, 2, 10, TimeUnit.SECONDS);
        ScheduledFuture future3 = executor.scheduleAtFixedRate(() -> {
            System.out.printf("%03ds: This is the third runnable, reporting in%n", (System.currentTimeMillis() - start) / 1000);
        }, 5, 15, TimeUnit.SECONDS);

        // Wait some
        Thread.sleep(30000);

        // Reschedule the second task
        System.out.printf("%03ds: Rescheduling the second runnable to run at 20 second intervals%n", (System.currentTimeMillis() - start) / 1000);
        future2.cancel(true);
        future2 = executor.scheduleAtFixedRate(() -> {
            System.out.printf("%03ds: This is the second runnable, reporting in%n", (System.currentTimeMillis() - start) / 1000);
        }, 2, 20, TimeUnit.SECONDS);
    }
}

正如您在下面的输出中看到的，重新安排第二个任务会重置它并将其从每 10 秒运行一次更改为每 20 秒运行一次，并且第一个和第三个任务不受影响。

输出:

000s: This is the first runnable, reporting in
002s: This is the second runnable, reporting in
005s: This is the first runnable, reporting in
005s: This is the third runnable, reporting in
010s: This is the first runnable, reporting in
012s: This is the second runnable, reporting in
015s: This is the first runnable, reporting in
020s: This is the first runnable, reporting in
020s: This is the third runnable, reporting in
022s: This is the second runnable, reporting in
025s: This is the first runnable, reporting in
030s: This is the first runnable, reporting in
030s: Rescheduling the second runnable to run at 20 second intervals
032s: This is the second runnable, reporting in
035s: This is the first runnable, reporting in
035s: This is the third runnable, reporting in
040s: This is the first runnable, reporting in
045s: This is the first runnable, reporting in
050s: This is the first runnable, reporting in
050s: This is the third runnable, reporting in
052s: This is the second runnable, reporting in
055s: This is the first runnable, reporting in
060s: This is the first runnable, reporting in
065s: This is the first runnable, reporting in
065s: This is the third runnable, reporting in
070s: This is the first runnable, reporting in
072s: This is the second runnable, reporting in