FutureTask.get方法永远阻塞，虽然我从另一个线程设置它的值(FutureTask.get method is blocking forever, although I am setting it's value from another thread)

 我试图使用下面的FutureResult类在两个线程之间发出信号，该类扩展了FutureTask类。 运行脚本时，它会打印以下结果。 
 
 发送：0 
 SENT：0 POLL：FutureResult @ 513431 
 SIGNALED：FutureResult @ 513431 
 
 然后程序永远挂断。 我希望FutureResult实例应该从它的阻塞get方法返回值。 然后在控制台中打印结果。 但FutureResult.get永远阻止。 
 
import java.util.concurrent.*;

/**
 * Created by someone on 20/08/2015.
 */
final public class FutureResult<T> extends FutureTask<T> {
    private static final Object SS = "SS";

    public FutureResult() {
        super(() -> null);
    }

    public void signal(final T value) {
        set(value);
    }

    public void signalError(final Throwable throwable) {
        setException(throwable);
    }

    public static void main(String... args) throws Exception {
        final ArrayBlockingQueue<FutureResult> queue = new ArrayBlockingQueue<>(1000000);
        new Thread(() -> {
            while (true) {
                try {
                    final FutureResult poll = queue.take();
                    System.out.println("POLL: " + poll);
                    if (poll != null) {
                        poll.signal(SS);
                        System.out.println("SIGNALLED: " + poll);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }).start();

        new Thread(() -> {

            for (int i = 0; i < 1; i++) {
                final FutureResult<Object> result = new FutureResult<>();
                System.out.println("SENDING: " + i);
                queue.offer(new FutureResult());
                try {
                    System.out.println("SENT: " + i);
                    result.get();
                    System.out.println("GOT : " + i);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                }
            }

        }).start();
    }
}

I am trying to signal between two threads using the below FutureResult class which extends FutureTask class. When run the script, it prints the following result. 
 
SENDING: 0
 SENT: 0 POLL: FutureResult@513431
 SIGNALLED: FutureResult@513431 
 
Then the program hang up forever. I expect FutureResult instance should return the value from it's blocking get method. Then print the result in the console. But FutureResult.get is blocking forever.
 
import java.util.concurrent.*;

/**
 * Created by someone on 20/08/2015.
 */
final public class FutureResult<T> extends FutureTask<T> {
    private static final Object SS = "SS";

    public FutureResult() {
        super(() -> null);
    }

    public void signal(final T value) {
        set(value);
    }

    public void signalError(final Throwable throwable) {
        setException(throwable);
    }

    public static void main(String... args) throws Exception {
        final ArrayBlockingQueue<FutureResult> queue = new ArrayBlockingQueue<>(1000000);
        new Thread(() -> {
            while (true) {
                try {
                    final FutureResult poll = queue.take();
                    System.out.println("POLL: " + poll);
                    if (poll != null) {
                        poll.signal(SS);
                        System.out.println("SIGNALLED: " + poll);
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }).start();

        new Thread(() -> {

            for (int i = 0; i < 1; i++) {
                final FutureResult<Object> result = new FutureResult<>();
                System.out.println("SENDING: " + i);
                queue.offer(new FutureResult());
                try {
                    System.out.println("SENT: " + i);
                    result.get();
                    System.out.println("GOT : " + i);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                } catch (ExecutionException e) {
                    e.printStackTrace();
                }
            }

        }).start();
    }
}

原文：https://stackoverflow.com/questions/32420624