为什么 Java 线程没有收到中断标志？

Question

我试图了解 ExecutorService 中的中断线程，但我无法弄清楚为什么以下 MyNeverEndingRunnable class 没有获得中断信号。我有一个 class 实现了 Runnable 并且简单地打印并循环等待直到它被中断：

class MyNeverEndingRunnable
    implements Runnable
{
    int count = 0;

    @Override
    public void run()
    {
        while (true)
        {
            System.out.printf("[%d]:%d\n", Thread.currentThread().getId(), ++count);
            try { Thread.sleep(5000L); } catch (Exception ignored) {}

            if (Thread.interrupted())
            {
                break;
            }
        }
    }
}

我生成了一些这样的线程，然后在我的 ExecutorService 上调用 shutdownNow() ，它应该在每个运行ning 线程上调用中断，但下面的代码将永远运行继续：

int threadCount = 5;
ExecutorService executorService = Executors.newFixedThreadPool(threadCount);
Future[] threads = new Future[threadCount];
for (int k = 0; k < threadCount; ++k)
{
    threads[k] = executorService.submit(new MyNeverEndingRunnable());
}

Thread.sleep(20000L);

executorService.shutdownNow();
while (!executorService.isShutdown()) Thread.sleep(1000L);

有人知道我做错了什么吗？

Answer 1

来自Javadoc：

InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown. [My emphasis]

NB 没有任何东西可以真正保证线程被 shutdownNow() 中断。它只是将其描述为 'typical implementation'.

你的代码有点奇怪。试试这个：

try
{
    Thread.sleep(5000L);
}
catch (InterruptedException exc)
{
    break;
}

并删除 Thread.interrupted() 测试。

Answer 2

阅读 Javadoc on Thread.sleep():

Throws: ... InterruptedException - if any thread has interrupted the current thread. The interrupted status of the current thread is cleared when this exception is thrown.

一抛出异常，就不再中断了。在您的情况下，您可以立即跳出循环并让线程终止，正如@EJP 所建议的那样。但是，如果您的代码没有线程的所有权（例如，一个单独的方法），您需要确保将中断传播给调用者，或者通过传播异常，或者通过重新中断：

try {
    while (true) {
        System.out.printf("[%d]:%d\n", Thread.currentThread().getId(), ++count);
        Thread.sleep(5000L);
    }
} catch (InterruptedException notIgnored)
    Thread.currentThread().interrupt();
}

或类似的：

while (!Thread.currentThread().isInterrupted()) {
    System.out.printf("[%d]:%d\n", Thread.currentThread().getId(), ++count);
    try {
        Thread.sleep(5000L);
    } catch (InterruptedException notIgnored)
        Thread.currentThread().interrupt();
    }
}

为什么 Java 线程没有收到中断标志？

Why doesn't Java Thread receive interrupt flag?

java

multithreading

interrupt

executorservice

threadpoolexecutor