Java多线程仅在完成时调用其他

Question

ExecutorService executor = Executors.newFixedThreadPool(10);

Runnable firstWorker = new DataComparison(DataComparison.FIRST_THREAD_INSTANCE,args[0], args[1], args[2], runSkey, fic_mis_date,legal_entity, args[6],failover);
executor.execute(firstWorker);

Runnable secondWorker = new DataComparison(DataComparison.SECOND_THREAD_INSTANCE,args[0], args[1], args[2], runSkey, fic_mis_date,legal_entity, args[6],failover);
executor.execute(secondWorker);

Runnable thirdWorker = new DataComparison(DataComparison.THIRD_THREAD_INSTANCE,args[0], args[1], args[2], runSkey, fic_mis_date,legal_entity, args[6],failover);
executor.execute(thirdWorker);

this is my code wherein i want to invoke second and third thread only when first has completed processing. I am confused between AwaitTermination and sleep . Kindly suggest.

Answer 1

With Java 8 CompletableFuture you can write

 ExecutorService executor = Executors.newFixedThreadPool(10);
 Runnable firstWorker = new DataComparison(DataComparison.FIRST_THREAD_INSTANCE,args[0], args[1], args[2], runSkey, fic_mis_date,legal_entity, args[6],failover);


 Runnable secondWorker = new DataComparison(DataComparison.SECOND_THREAD_INSTANCE,args[0], args[1], args[2], runSkey, fic_mis_date,legal_entity, args[6],failover);


  Runnable thirdWorker = new DataComparison(DataComparison.THIRD_THREAD_INSTANCE,args[0], args[1], args[2], runSkey, fic_mis_date,legal_entity, args[6],failover);

 CompletableFuture firstTask = CompletableFuture.runAsync(firstWorker,
          executor);
 firstTask.thenRunAsync(secondWorker,executor)
 firstTask.thenRunAsync(thirdWorker,executor);

This will start the second and third tasks when the first completes.

Answer 2

If I understand your question correctly, using Guava's support for futures might be really helpful. I would refer to this article by google to learn a little bit more about ListenableFuture . Here is a code sample based on your code, though if you do plan to use Guava's Futures, I would probably build my code a bit differently:

    ListeningExecutorService s = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(10));
    Runnable firstWorker = new DataComparison(1);

    final Runnable secondWorker = new DataComparison(2);

    final Runnable thirdWorker = new DataComparison(3);

    ListenableFuture f = s.submit(firstWorker);

    Futures.addCallback(f, new FutureCallback() {
        @Override
        public void onSuccess(Object o) {
            secondWorker.run();
        }

        @Override
        public void onFailure(Throwable throwable) {
        }
    });

    Futures.addCallback(f, new FutureCallback() {
        @Override
        public void onSuccess(Object o) {
            thirdWorker.run();
        }

        @Override
        public void onFailure(Throwable throwable) {
        }
    });

What happens here is that first we submit the first worker, and then add 2 callbacks to it ( secondWorker and thirdWorker ). The onSuccess method will be called once firstWorker completes successfully. If it throws an exception, onFailure will be called.

Answer 3

Here's a simple possibility. There are other more complicated things that you could do, but if I understand your question correctly, this should do what you want:

final Runnable firstWorker = new DataComparison(DataComparison.FIRST_THREAD_INSTANCE,args[0], args[1], args[2], runSkey, fic_mis_date,legal_entity, args[6],failover);
final Runnable secondWorker = new DataComparison(DataComparison.SECOND_THREAD_INSTANCE,args[0], args[1], args[2], runSkey, fic_mis_date,legal_entity, args[6],failover);
final Runnable thirdWorker = new DataComparison(DataComparison.THIRD_THREAD_INSTANCE,args[0], args[1], args[2], runSkey, fic_mis_date,legal_entity, args[6],failover);

Runnable combined = new Runnable() {
  @Override
  public void run() {
    firstWorker.run();
    executor.execute(secondWorker);
    executor.execute(thirdWorker);
  }
};

executor.execute(combined);