Exchanger示例

Exchanger有两个用户，当一(A)方调用exchange方法之后，就开始等待，直到另一(B)方开始调用exchange方法。两个exchange可以认为是原子性的。

public class Core {
    public static void main(String[] args) {
        List<String> buffer1 = new ArrayList<>();
        List<String> buffer2 = new ArrayList<>();

        Exchanger<List<String>> exchanger = new Exchanger<>();

        Producer producer = new Producer(buffer1, exchanger);
        Consumer consumer = new Consumer(buffer2, exchanger);

        Thread threadProducer = new Thread(producer);
        Thread threadConsumer = new Thread(consumer);
        threadProducer.start();
        threadConsumer.start();
    }
}

public class Producer implements Runnable {
    private List<String> buffer;
    private final Exchanger<List<String>> exchanger;

    public Producer(List<String> buffer, Exchanger<List<String>>
            exchanger) {
        this.buffer = buffer;
        this.exchanger = exchanger;
    }

    @Override
    public void run() {
        int cycle = 1;
        for (int i = 0; i < 19; i++) {
            System.out.printf("Producer: Cycle %d\n", cycle);
            for (int j = 0; j < 8; j++) {
                String message = "Event " + ((i * 19) + j);
                System.out.printf("Producer: %s\n", message);
                buffer.add(message);
            }

            try {
                buffer = exchanger.exchange(buffer);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("Producer: " + buffer.size());
            cycle++;
        }
    }
}

public class Consumer implements Runnable {

    private List<String> buffer;

    private final Exchanger<List<String>> exchanger;

    public Consumer(List<String> buffer, Exchanger<List<String>>
            exchanger) {
        this.buffer = buffer;
        this.exchanger = exchanger;
    }

    @Override
    public void run() {
        int cycle = 1;
        for (int i = 0; i < 19; i++) {
            System.out.printf("Consumer: Cycle %d\n", cycle);

            try {
                buffer = exchanger.exchange(buffer);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            System.out.printf("Consumer: Cycle %d, total %d\n ", cycle, buffer.size());
            for (int j = 0; j < 8; j++) {
                String message = buffer.get(0);
                System.out.printf("Consumer: Cycle %d %s\n", cycle, message);
                buffer.remove(0);
            }
            cycle++;
        }

    }
}