java - FutureTask 似乎没有中断

Question

我正在制作一些虚拟程序来了解这个 Java 类。我的定时任务调用了一个什么也不做的任务，在中断它之前给它 3 秒的时间。这是代码:

FutureTask<Integer> task = new FutureTask<>(new
            Callable<Integer>(){
                @Override
                public Integer call() throws Exception {
                    int i =0;
                    while(i<100000){
                        ;
                    }

                    return 0;
                }

    });

    executor.execute(task);
    try {
        task.get(3000, TimeUnit.MILLISECONDS);
        System.out.println("Everything was ok");
    } catch (InterruptedException | ExecutionException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (TimeoutException ex){
        boolean result = task.cancel(true); //here i cancel the thread  
        System.out.println("the task has timed out "+result);
    }

发生的情况是执行了 catch block ，但我的程序一直运行到线程完成为止。这就像 task.cancel 没有被接受。这是为什么？

Answer 1

您的任务受计算限制。它不执行任何 IO 或 hibernate ，此时 JVM 检查中断标志(任何抛出 InterruptedException 的方法)。因此，您的任务是不可中断的。

Interrupt 值得一读教程。注意:

What if a thread goes a long time without invoking a method that throws InterruptedException? Then it must periodically invoke Thread.interrupted, which returns true if an interrupt has been received. For example:

for (int i = 0; i < inputs.length; i++) {
    heavyCrunch(inputs[i]);
    if (Thread.interrupted()) {
        // We've been interrupted: no more crunching.
        return;
    }
}

还有

The interrupt mechanism is implemented using an internal flag known as the interrupt status. Invoking Thread.interrupt sets this flag. When a thread checks for an interrupt by invoking the static method Thread.interrupted, interrupt status is cleared. The non-static isInterrupted method, which is used by one thread to query the interrupt status of another, does not change the interrupt status flag.

请注意，人们经常会这样写:

 try {
   // interruptible operation
 }
 catch (InterruptedException e) {
   // do nothing
 }

这不会重置中断标志。这导致不可中断的代码。参见 this JavaSpecialists newsletter了解更多信息