Failing to call shutdown()
on a thread executor will result in a never terminating application.
Best practice to shut down the ExecutorService is this:
ExecutorService service = null;
try {
service = Executors.newSingleThreadExecutor();
// add tasks to thread executor
…
} finally {
if (service != null) service.shutdown();
}
Since Java knows the try-with-resources concept, wouldn't it be nice if we could do this?
try (service = Executors.newSingleThreadExecutor())
{
// add tasks to thread executor
…
}
That ExecutorService has actually two shutdown-related methods; based on the simple fact that both ways of shutting down a service make sense.
Thus: how would you auto-close a service then? In a consistent manner that works for everybody?!
So, the reasonable explanation in my eyes: you can't make an ExecutorService a AutoClosable because that service does not have a single "close" like operation; but two!
And if you think you could make good use of such an auto-closing service, writing up your own implementation using "delegation" would be a 5 minute thing! Or probably 10 minutes, because you would create one version calling
shutdown()
as close operation; and one that doesshutdownNow()
instead.