up vote
22
down vote
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What is the difference between
ExecutorService eService = Executors.newFixedThreadPool(2);
eService.execute(new TestThread6());
eService.execute(new TestThread6());
eService.execute(new TestThread6());
eService.awaitTermination(1, TimeUnit.NANOSECONDS);
eService.shutdown();
and
eService.shutdown();
eService.awaitTermination(1, TimeUnit.NANOSECONDS);
I don’t really understand shutdown(). This method does not wait for previously submitted tasks to complete execution. Does it mean shutdown() may terminate the tasks which have been submitted, but not completed? I tried some examples, they do not prove it, please give me an example.
up vote
15
down vote
shutdown means the executor service takes no more incoming tasks.
awaitTermination is invoked after a shutdown request.
You need to first shut down the service and then block and wait for threads to finish.
If you want to see all threads finish running and insist on using awaiTermination, you need to set the timeout parameter to be big enough. So you could do:
eService.shutdown();
if (!eService.awaitTermination(60000, TimeUnit.SECONDS))
System.err.println(“Threads didn’t finish in 60000 seconds!”);
}
Alternatively, you could do:
eService.shutdown();
while (!eService.isTerminated()) {
}
This way you are able to ensure all threads are finished running unless they are interrupted unexpectedly.