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I was using Executors.newSingleThreadExecutor() and I am a bit confused about how it works. Let's say I am not calling shutdown(). I looked at the available source code http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/java/util/concurrent/Executors.java#Executors.newSingleThreadExecutor%28%29 and it says:

public static ExecutorService  newSingleThreadExecutor() {
  return new FinalizableDelegatedExecutorService(new ThreadPoolExecutor(1, 1,
     0L, TimeUnit.MILLISECONDS,
        new LinkedBlockingQueue<Runnable>()));
}

So, my assumption is after a task is executed even if I do not call shutdown() the thread should be stopped and a new Thread should be created if I call a task again on the same executor. But when I ran a code it gave a different output. Can someone explain the behavior? Here's the code:

public static void main(String[] args) throws InterruptedException, ExecutionException {
    ExecutorService es = Executors.newSingleThreadExecutor();
    Future<String> f = es.submit(new MyService());
    System.out.println(f.get());
    System.out.println("Done executing 1st run");
    Thread.sleep(3000);
    f = es.submit(new MyService());
    System.out.println(f.get());
    es.shutdown();
}


public class MyService implements Callable<String>{

    @Override
    public String call() throws Exception {
        System.out.println("Old name: " + Thread.currentThread().getName());
        Thread.currentThread().setName("Mythread: " + Math.random());
        return Thread.currentThread().getName();
    }

}

Here's the output:

Old name: pool-1-thread-1
Mythread: 0.061937241356848194
Done executing 1st run
Old name: Mythread: 0.061937241356848194
Mythread: 0.49829755639701667

I thought the Old name: in the 4th line should be pool-1-thread-1 as the existing thread has a timeout of 0L. So, a new thread should be created. Instead it is using the previous thread

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1 回答 1

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You have set the maximum and minimum number of threads to 1,so the timeout is ignored because there will never be any additional threads to timeout.

The output you give doesn't make sense as there is no thread name the second time. Also if your thread stopped and a new one created, it would be called pool-1-thread-2

于 2014-12-27T19:53:02.797 回答