How to find out if the thread/task started by Executor.execute() ( not ExecutorService ) completed?

Question

In Java, Executor class does not have shutdown/shutdownNow()/awaitTermination like ExecutorService subclass. So if you start a task/thread by invoking executorObject.execute(runnableTask), how can you check if that task completed ?

Answer 1

You can't do it with Executor simply because it provides a single method void execute(Runnable) . Unless you consider using Executor implementations that return Future , you can implement notify/wait mechanism of your own:

final CountDownLatch latch = new CountDownLatch(1);
Runnable task = () -> {
   try {
      // ... do useful work
   } finally {
      latch.countDown();
   }
}

executorObject.execute(task);

// wrap into try/catch for InterruptedException
// if not propagating further
latch.await(); // await(timeout);