Question

I need to create async thread that runs once with a delay of 2 minutes and that can be killed at any moment. I saw several possible solutions:

1. ScheduledExecutorService and FutureTask allow me to interrupt a running task, but I will have to invoke shutdown() to terminate all the running threads, and this will block user until the processes were terminated. Also, I will have to frequently invoke Thread.interrupted() as described in Enno Shioji’s answer.
2. Timer and TimerTask do not require to release running threads, but I have no way to interrupt a running timer thread (Timer.cancel() just cancels future scheduling)
3. Using Thread and sleep with thread interruption problem.

Is there a good solution? (I’m using tomcat 7)

thank you

Answer 1

After some tests and researches, FutureTask.cancel() and Threads need similar handling of interrupts, as stated in Enno Shioji’s answer

1. Check interruption flag in your logic
2. Act upon Interrupted exception

An example that tests interruption flag:

private final class MyTask implements Runnable {

    public void run() {
        try{
            for(int j=0; j<100000000; j++) {
                for(int i=1; i<1000000000; i++){
                    if(Thread.interrupted()){ //Don't use Thread.interrupt()!
                        Log.debug("Thread was interrupted for" + cache);
                        return; //Stop doing what you are doing and terminate.
                    }
                    Math.asin(0.1565365897770/i);
                    Math.tan(0.4567894289/i);
                }
            }                            
        }catch(Throwable e){//if exception is uncaught, the scheduler may not run again 
            ...
        }
    }
}

As I understand, ScheduledExecutorService maybe be shutdown when application ends running