Best way to identify and dispose locked thread in java.

Question

I have to call a function 3rd party module on a new thread. From what I've seen, the call either completes quickly if everything went well or it just hangs for ever locking up the thread. What's a good way to start the thread and make the call and wait for a few secs and if the thread is still alive, then assuming it's locked up, kill (or stop or abandon) the thread without using any deprecated methods.

I have something like this for now, but I'm not sure if this is the best way to do it and I want to avoid calling Thread.stop() as it's deprecated. Thanks.

private void foo() throws Exception
{
        Runnable runnable = new Runnable()
        {

            @Override
            public void run()
            {
                    // stuff that could potentially lock up the thread.
            }
        };
        Thread thread;
        thread = new Thread(runnable);
        thread.start();
        thread.join(3500);
        if (thread.isAlive())
        {
            thread.stop();
            throw new Exception();
        }

}

Answer 1

I would look into the java.util.concurrent Executor framework and specifically the Future<T> interface. with these you are abstracted somewhat from the vagaries of java.lang.Thread, and you get good decoupling of what the tasks are from how they are run (whether on a separate thread, whether the thread comes from a pool or is instantiated on the fly, etc.)

A Future instance, at least, gives you isDone and isCancelled methods.

The ExecutorService (subinterface of Executor) gives you some means of shutting down any outstandings tasks. Or check out the ExecutorService.awaitTermination(long timeout, TimeUnit unit) method

private void foo() throws Exception
{
        ExecutorService es = Executors.newFixedThreadPool(1);

        Runnable runnable = new Runnable()
        {

            @Override
            public void run()
            {
                    // stuff that could potentially lock up the thread.
            }
        };

        Future result = es.submit(runnable);

        es.awaitTermination(30, TimeUnit.SECONDS);

        if (!result.isDone()){
            es.shutdownNow();
        }

}

Answer 2

public void stop() {
        if (thread != null) {
           thread.interrupt();
        }
    }

See this link on How to Stop a Thread, it covers the subject well

Answer 3

There is no way to do what you want (unconditionally). For example if the stuff that could potentially lock up the thread. looks like this, there is no way to stop it, ever short of System.exit():

public void badStuff() {
 while (true) {
  try {
   wait();
  }
  catch (InterruptedException irex) {
  }
 }
}

When your app gets stuck, run jstack (or use the debugger). Try to figure out what sticks up the function and fix it.