How do I call some blocking method with a timeout in Java?

Is there a standard nice way to call a blocking method with a timeout in Java? I want to be able to do:

// call something.blockingMethod();
// if it hasn't come back within 2 seconds, forget it

if that makes sense.

Thanks.

You could use an Executor:

ExecutorService executor = Executors.newCachedThreadPool();
Callable<Object> task = new Callable<Object>() {
   public Object call() {
      return something.blockingMethod();
   }
};
Future<Object> future = executor.submit(task);
try {
   Object result = future.get(5, TimeUnit.SECONDS); 
} catch (TimeoutException ex) {
   // handle the timeout
} catch (InterruptedException e) {
   // handle the interrupts
} catch (ExecutionException e) {
   // handle other exceptions
} finally {
   future.cancel(true); // may or may not desire this
}

If the future.get doesn't return in 5 seconds, it throws a TimeoutException. The timeout can be configured in seconds, minutes, milliseconds or any unit available as a constant in TimeUnit.

See the JavaDoc for more detail.

You could wrap the call in a FutureTask and use the timeout version of get().

See http://java.sun.com/j2se/1.5.0/docs/api/java/util/concurrent/FutureTask.html

See also Guava's TimeLimiter which uses an Executor behind the scenes.

It's really great that people try to implement this in so many ways. But the truth is, there is NO way.

Most developers would try to put the blocking call in a different thread and have a future or some timer. BUT there is no way in Java to stop a thread externally, let alone a few very specific cases like the Thread.sleep() and Lock.lockInterruptibly() methods that explicitly handle thread interruption.

So really you have only 3 generic options:

Put your blocking call on a new thread and if the time expires you just move on, leaving that thread hanging. In that case you should make sure the thread is set to be a Daemon thread. This way the thread will not stop your application from terminating.
Use non blocking Java APIs. So for network for example, use NIO2 and use the non blocking methods. For reading from the console use Scanner.hasNext() before blocking etc.
If your blocking call is not an IO, but your logic, then you can repeatedly check for Thread.isInterrupted() to check if it was interrupted externally, and have another thread call thread.interrupt() on the blocking thread

This course about concurrency https://www.udemy.com/java-multithreading-concurrency-performance-optimization/?couponCode=CONCURRENCY

really walks through those fundamentals if you really want to understand how it works in Java. It actually talks about those specific limitations and scenarios, and how to go about them in one of the lectures.

I personally try to program without using blocking calls as much as possible. There are toolkits like Vert.x for example that make it really easy and performant to do IO and no IO operations asynchronously and in a non blocking way.

I hope it helps

There is also an AspectJ solution for that with jcabi-aspects library.

@Timeable(limit = 30, unit = TimeUnit.MINUTES)
public Soup cookSoup() {
  // Cook soup, but for no more than 30 minutes (throw and exception if it takes any longer
}

It can't get more succinct, but you have to depend on AspectJ and introduce it in your build lifecycle, of course.

There is an article explaining it further: Limit Java Method Execution Time

How do I call some blocking method with a timeout in Java?

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