Shutdown Java Executor After All Submitted Tasks Finished Without Blocking

Question

I'm wondering if there is a way to shutdown a Java ExecutorServiceand allow all submitted tasks to finish while not blocking.

to be more specific, I want to schedule a Runnable with a delay and continue with the code, without the need to keep a reference to the ExecutorService to be able to shut it down.

The following code will terminate the submitted task as it hasn't started yet:

ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();
executor.schedule(runnable, delay, TimeUnit.MILLISECONDS);
executor.shutdown();
...

While this code will block until the task is finished:

ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();
executor.schedule(runnable, delay, TimeUnit.MILLISECONDS);
executor.awaitTermination(timeout, TimeUnit.MILLISECONDS);
...

I want to have something like this:

ScheduledExecutorService executor = Executors.newSingleThreadScheduledExecutor();
executor.schedule(runnable, delay, TimeUnit.MILLISECONDS);
executor.shutdownAfterTerminationWithoutBlocking();
...
code that runs without waiting

I know this possible using Timer but i'm wondering if this is possible using ExecutorService

Answer 1

ExecutorService.shutdown javadoc says:

Initiates an orderly shutdown in which previously submitted tasks are executed, but no new tasks will be accepted.

So tasks that already submitted, but not yet started, will be executed. Exactly as you need.