ExecutorService, how to wait for all tasks to finish

Question

What is the simplest way to to wait for all tasks of ExecutorService to finish? My task is primarily computational, so I just want to run a large number of jobs

Answer 1

Just use

latch = new CountDownLatch(noThreads)

In each thread

latch.countDown();

and as barrier

latch.await();

Answer 2

Submit your tasks into the Runner and then wait calling the method waitTillDone() like this:

Runner runner = Runner.runner(2);

for (DataTable singleTable : uniquePhrases) {

    runner.run(new ComputeDTask(singleTable));
}

// blocks until all tasks are finished (or failed)
runner.waitTillDone();

runner.shutdown();

To use it add this gradle/maven dependency: 'com.github.matejtymes:javafixes:1.0'

For more details look here: https://github.com/MatejTymes/JavaFixes or here: http://matejtymes.blogspot.com/2016/04/executor-that-notifies-you-when-task.html

Answer 3

If you want to wait for the executor service to finish executing, call shutdown() and then, awaitTermination(units, unitType), e.g. awaitTermination(1, MINUTE). The ExecutorService does not block on it's own monitor, so you can't use wait etc.