Question

From the main thread:

executorService.submit(new Runnable() { ... });

Now when Runnable has finished executing, is there the Java’s standard way of signaling the caller thread that it has finished executing, without making a new interface/listener class?

Bonus points if the signal can be emitted from the caller thread.

Answer 1

submit returns a Future on which the submitting thread can call get to block until the task completes.

Future<?> future = executor.submit(new Runnable() { ... });
future.get();