Java并发（十六）：并发工具类——Exchanger

Posted 2021-01-21 hexinwei1

Exchanger（交换者）是一个用于线程间协作的工具类。Exchanger用于进行线程间的数据交换。它提供一个同步点，在这个同步点两个线程可以交换彼此的数据。这两个线程通过exchange方法交换数据， 如果第一个线程先执行exchange方法，它会一直等待第二个线程也执行exchange，当两个线程都到达同步点时，这两个线程就可以交换数据，将本线程生产出来的数据传递给对方。

举例

class ExchangerTest {

    static class Producer implements Runnable {

        // 生产者、消费者交换的数据结构
        private List<String> buffer;

        // 步生产者和消费者的交换对象
        private Exchanger<List<String>> exchanger;

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

        @Override
        public void run() {
            for (int i = 1; i < 5; i++) {
                for (int j = 1; j <= 3; j++) {
                    System.out.println("生产者装入" + i + "--" + j);
                    buffer.add("buffer：" + i + "--" + j);
                }

                System.out.println("生产者装满，等待与消费者交换...");
                try {
                    exchanger.exchange(buffer);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.err.println("生产者 " + i + ":" + buffer);
            }
        }
    }

    static 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() {
            for (int i = 1; i < 5; i++) {
                // 调用exchange()与消费者进行数据交换
                try {
                    buffer = exchanger.exchange(buffer);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                System.out.println("消费者第" + i + "次提取");
                for (int j = 1; j <= 3; j++) {
                    System.out.println("消费者 : " + buffer.get(0));
                    buffer.remove(0);
                }
            }
        }
    }

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

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

        Thread producerThread = new Thread(new Producer(buffer1, exchanger));
        Thread consumerThread = new Thread(new Consumer(buffer2, exchanger));

        producerThread.start();
        consumerThread.start();
    }
}

 

 

并发工具类（四）两个线程进行数据交换的Exchanger

【死磕Java并发】—–J.U.C之并发工具类：Exchanger