how to check if all threads in executor service is done

Question

I'm trying to calculate some metrics, once all the threads in the myclass are done, the job is done for the thread once i reach the timeout scenario, which i able to hit for every thread. Now in the main () method in the Group class how can i wait for all the myclass threads to complete ?

I dont want to use any sleep() scenario

Group Class class myGroup { public void run(int numThreads) { executor = Executors.newFixedThreadPool(numThreads); executor.submit(new myclass(threadNumber)); } public static void main(String[] args) { run(noOfthreads); // Collect metrics once all the myclass threads are done. } }

myclass

 class myclass implements Runnable { try{ } catch(SomeTimeoutException cte){ // Job Done for thread } }

You might want to take a look at java.util.concurrent.CountDownLatch — xiaofeng.li
– xiaofeng.li, Commented Aug 10, 2016 at 23:35

Community · Accepted Answer · 2017-05-23 12:01:00Z

Could do something like this:

List<myclass> tasks = makeAListOfMyClassTasks(); // this will kick off all your tasks at once: List<Future<myclass>> futures = executor.invokeAll(tasks); // this will wait until all your tasks are done, dead, or the specified time has passed executor.awaitTermination(10, TimeUnit.MINUTES); // change this to your liking // check each Future to see what the status of a specific task is and do something with it for (Future<myclass> future : futures) { if (future.isCancelled()) { // do something } else if (future.isDone()) { myclass task = future.get(); // this will block if it's not done yet task.whatever(); } }

@beatngu13 also pointed out this nifty class ExecutorCompletionService; so you could do something like this:

List<myclass> tasks = makeAListOfMyClassTasks(); CompletionService<Result> ecs = new ExecutorCompletionService<Result>(exectuor); for (myclass t : tasks) { // this kicks off the task and returns a Future, which you could gather ecs.submit(t); } for (int i = 0; i < tasks.length(); i ++) { myclass task = ecs.take().get(); // this will block until the next task is done/dead // ... do something with task }

Info on futures: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/Future.html

This has examples for ExecutorService: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ExecutorService.html

This related thread is pretty relevant: ExecutorService, how to wait for all tasks to finish

Hope this helps.

@beatngu13 Ooo, fancy. I'll add a blurb but feel free to edit it too.

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