如何停止java executor类中的所有可运行线程？

Question

final ExecutorService executor = Executors.newFixedThreadPool(1);
final Future<?> future = executor.submit(myRunnable);
executor.shutdown();
if(executor.awaitTermination(10, TimeUnit.SECONDS)) {
  System.out.println("task completed");
}else{
  System.out.println("Executor is shutdown now");
}

//MyRunnable method is defined as task which I want to execute in a different thread.

Here is run method of executor class:

public void run() {
try {
     Thread.sleep(20 * 1000);
} catch (InterruptedException e) {
 // TODO Auto-generated catch block
 e.printStackTrace();
}}

Here it is waiting for 20 second but when i run the code it throws an exception:

java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)

I am not able to close the concurrent thread ruining in Java Executor class . Here is my Code flow:

• Created a new Thread with Java executor class to run some task ie written in MyRunnable
• executor wait for 10 second to complete the tasks.
• If the task has completed then runnable thread also got terminated.
• If the task is not completed within 10 second then executor class should terminate the thread.

Everything works fine except the termination of tasks in the last scenario. How should I do it?

Answer 1

The shutDown() method simply prevents additional tasks from being scheduled. Instead, you could call shutDownNow() and check for thread interruption in your Runnable .

// in your Runnable...
if (Thread.interrupted()) {
  // Executor has probably asked us to stop
}

An example, based on your code, might be:

final ExecutorService executor = Executors.newFixedThreadPool(1);
executor.submit(new Runnable() {
  public void run() {
    try {
      Thread.sleep(20 * 1000);
    } catch (InterruptedException e) {
      System.out.println("Interrupted, so exiting.");
    }
  }
});

if (executor.awaitTermination(10, TimeUnit.SECONDS)) {
  System.out.println("task completed");
} else {
  System.out.println("Forcing shutdown...");
  executor.shutdownNow();
}

Answer 2

It is generally a bad idea to terminate a running thread from the outside, because you don't know the state the thread is currently in. It's possible that it needs to do some cleanups, and it won't be able to do that when you forcefully shut it down. That's why all methods of Thread which do that are marked as deprecated .

It's much better to use one of the many techniques which are available for interprocess communication to signal the procedure running in the thread itself that it has to abort its work and exit normally. One way to do this is to add an abort() method to your runnable, which raises a flag declared as volatile . The inner loop of your Runnable checks that flag and exits (in a controlled fashion) when that flag is raised.