java - How do you make something like a thread that can be started and stopped?

Question

Is there a way to make something like a thread that does something every x amount of ms that I can start, stop, and resume when I want it to? I know that a thread can be started but there is no real safe way to stop and resume a thread.

Have a look at http://www.quartz-scheduler.org/ – Paul Medcraft Jan 16 '12 at 18:01 — Paul Medcraft, Jan 16 '12 at 18:01

score 4 · Answer 1 · edited May 23 '17 at 12:12

Here are a bunch of examples on how to start/stop periodic tasks in Java:

How to schedule a periodic task in Java? (basically executor service)
Schedule periodic tasks (a more detailed exploration into various ways to schedule periodic tasks)

The example from the first link:

private final ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
scheduler.scheduleAtFixedRate(yourRunnable, 8, 8, HOURS);

score 2 · Answer 2 · answered Jan 16 '12 at 17:58

2

You can use the java.util.Timer class to schedule tasks on a background worker thread.

answered Jan 16 '12 at 17:58

Tudor

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ScheduledExecutorService is a better alternative. – Scorpion Jan 16 '12 at 18:03
1

@Scorpion: If the task is simple, there is no need to use more complicated constructs. – Tudor Jan 16 '12 at 18:04
Tudor: using ScheduledExecutorService isn't complicated (atleast not more complicated than using Timers) as illustrated by @Lirik's answer. Also, this (http://stackoverflow.com/questions/409932/java-timer-vs-executorservice) discussion should give you some insight why Timer should be avoided. – Scorpion Jan 17 '12 at 07:46

score 2 · Answer 3 · answered Jan 16 '12 at 18:02

The javadocs of the thread pol executor has an example of creating a thread pool which can be paused/ resumed. Here is the link http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/ThreadPoolExecutor.html

It is not of industrial strength but should be enough to give you ideas.

score 1 · Answer 4 · answered Jan 16 '12 at 18:04

I believe what you're looking for is the Timer class, which will allow you to periodically executes the run method of a sub-class of TimerTask.

For recurring events, the example given at http://enos.itcollege.ee/~jpoial/docs/tutorial/essential/threads/timer.html (slightly modified and copied here for convenience) is :

 public class AnnoyingMessage {
    Timer timer;

    public AnnoyingBeep() {
        timer = new Timer();
        timer.schedule(new RemindTask(),
                       0,        //initial delay
                       1*1000);  //subsequent rate = once a second. 
    }

    class RemindTask extends TimerTask {
        int numWarningBeeps = 3;
        public void run() {
            if (numWarningBeeps > 0) {
                System.out.println(" MESSAGE!");
                numWarningBeeps--;
            } else {
                System.out.println("Done");
                timer.cancel(); 
            }
        }
    }
}

score 0 · Answer 5 · answered Jan 16 '12 at 17:59

There are definitely safe ways to stop threads. Read http://docs.oracle.com/javase/tutorial/essential/concurrency/interrupt.html. And pausing a thread and resuming it is simply a matter of setting a flag and using wait and notifyAll appropriately.

You're probably looking for a higher-level abstraction, though. Have a look at ScheduledExecutorService.

java - How do you make something like a thread that can be started and stopped?

5 Answers5