如何在超时x次后停止任务

Question

I am trying execute a runnable a few times, and if it doesn't finished within x seconds 3 times, I will cancel it.

The code I'm using to simulate the situation where the task needs to be cancelled is as follows. From the output I can see that an InterruptedException was thrown and caught accordingly, but the task keeps running.

It seems that the first two times the task was run before the TimeoutException was thrown 3 times, those two runs kept on running until they are finished. I'm wondering if there is a way to stop those two runs from completing ?

public class SomeClass {

private static int c =0;

public static void main(String[] args){
    Runnable dummyRunnable = new Runnable() {

        @Override
        public void run() {
            System.out.println("Hello from dummyRunnable!");        

                for (int i =0; i< 10; i++){
                    try {
                        //simulate work here
                        if (!Thread.currentThread().isInterrupted()) Thread.sleep(5000);
                        System.out.println("thread sleeps for the " + i + " time!");    
                    } catch (InterruptedException ie){
                        System.out.println("InterruptedException catched in dummyRunnable!");   
                        //Thread.currentThread().interrupt(); //this has no effects
                        break;

                    }
                }



        }
    }; 


    BlockingQueue<Runnable> blockingQueue = new ArrayBlockingQueue<Runnable>(10 * 3, true);
    ThreadPoolExecutor executor = new ThreadPoolExecutor(3, 3, Long.MAX_VALUE, TimeUnit.MILLISECONDS, blockingQueue);

    for (int i =0; i< 5; i++){
        Future<?> task = executor.submit(dummyRunnable);

        try{
            Thread.sleep(1000);
            task.get(2000, TimeUnit.MILLISECONDS);
        } catch (TimeoutException te){
            c++;
            System.out.println("TimeoutException from a task!");
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (ExecutionException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            if (c==3){
                System.out.println("cancelling task...");
                task.cancel(true);
                break;
            }
        }
    }
     }
}

Answer 1

I don't get it what you are actually trying to simulate. I would expect a simulation like paying with card (60 secs time-out to finish a task) or perhaps a secretary in a doctor-patient situation.

The way it stand now you are creating the 5 objects in the Future. If you want more control off your threads, you should think about using synchronized methods and a monitor that handles the threads for you.

Usually when starting a thread you should go with

new Thread(new Task(object or generics)).start();
Thread.sleep(2000); // calls this thread to wait 2 secs before doing other task(s)

Before doing some hardcore concurrency(multithreading), you should read some java tutorial to get some inspiration... http://docs.oracle.com/javase/tutorial/essential/concurrency/index.html