Question

I got a loop {Loop-1}, where I start Threads. The class which contains the {Loop-1} implements Daemon and Runnable.
In the {Loop-1} the thread, which is started, calls a method coordinate() of a class Coordinate.java where I use the ExecutorService.

When the object of Coordinate.java is created (this happens once BEFORE {Loop-1}), I instantiate a ExecutorService
pool = Executors.newFixedThreadPool(2);

In coordinate() I create two Objects of a class which implements Callable and I start them then and store the result in a List of Future results.
callableResults = pool.invokeAll(threads);

After, I try to get the results in a loop with result = future.get();

Then, I return to {Loop-1} and the whole process starts again (call coordinate(), invokeAll(), future.get()

Now Ive got the following question:
1. Do I need to shutdown the pool of ExecutorService after I got the results in coordinate()?
2. Do I need to recreate the pool everytime my {Loop-1} calls coordinate()?

Thanks for answers! 🙂

Answer 1

You need to shutdown the executorService once you’re done processing all your tasks.
The submission of tasks can be in multiple cycles.

Once you call executorService.shutDown(), you can wait until all tasks are completed after calling shutDown() using executorService.awaitTermination(10, TimeUnit.SECONDS).

Alternatively, you can do: while (!executorService.isTerminated()) { }