java多线程编程 | producer - consumer问题中_producer-consumer unit buffer-优快云博客

本文探讨了如何利用Java的BlockingQueue来避免生产者在缓冲区满时添加数据，以及消费者在缓冲区空时尝试消费数据的问题。生产者在buffer满时会被阻塞，而消费者在buffer空时也会被阻塞，直至条件满足后再继续执行。

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关键：生产者不会在缓冲区满时加入数据，消费者不会在缓冲区空时消费数据

生产者持续生产，直到buffer满，满时阻塞；buffer不满后，继续生产
消费者持续消费，直到buffer空，空时阻塞；buffer不空后，继续消费

方法1: BlockingQueue实现

class Producer implements Runnable {
    private BlockingQueue<Integer> queue;
    private static AtomicInteger count = new AtomicInteger(0);
    private static final int SLEEPTIME = 1000;
    private volatile boolean isRunning = true;

    public Producer(BlockingQueue<Integer> queue) {
        this.queue = queue;
    }

    @Override
    public void run() {
        int data;
        Random random = new Random();
        System.out.println("start producer id = " + Thread.currentThread().getId());
        while (isRunning) {
            try {
                Thread.sleep(random.nextInt(SLEEPTIME));
                data = count.incrementAndGet();
                System.out.println("producer " + Thread.currentThread().getId() + " create data：" + data
                        + ", size：" + queue.size());
                if (!queue.offer(data, 2, TimeUnit.SECONDS)) {
                    System.err.println("failed to put data: " + data);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

    public void stop() {
        isRunning = false;
    }
}

class Consumer implements Runnable {
    private BlockingQueue<Integer> queue;
    private static final int SLEEPTIME = 1000;

    public Consumer(BlockingQueue<Integer> queue) {
        this.queue = queue;
    }

    @Override
    public void run() {
        Random random = new Random();
        System.out.println("start consumer {id} = " + Thread.currentThread().getId());
        while (true) {
            try {
                Thread.sleep(random.nextInt(SLEEPTIME));
                if (queue.isEmpty()) {
                    System.out.println("Queue is empty, consumer " + Thread.currentThread().getId()
                            + " is waiting, size：" + queue.size());
                } else {
                    int data = queue.take();
                    System.out.println("consumer {" + Thread.currentThread().getId() + "} consume data：" + data
                            + ", size：" + queue.size());
                }

            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

class BlockingQueueSolution {
    public void test() {
        ExecutorService executorService = Executors.newCachedThreadPool();
        BlockingQueue<Integer> blockingQueue = new LinkedBlockingDeque<>(20);
        Producer producer1 = new Producer(blockingQueue);
        Producer producer2 = new Producer(blockingQueue);
        Producer producer3 = new Producer(blockingQueue);

        Consumer consumer = new Consumer(blockingQueue);
        executorService.submit(producer1);
        executorService.submit(producer2);
        executorService.submit(producer3);
        executorService.submit(consumer);

        try {
            Thread.sleep(20 * 1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        producer1.stop();
        producer2.stop();
        producer3.stop();

        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        executorService.shutdown();
    }
}

public class ProducerConsumer {
    public static void main(String[] args) {
        BlockingQueueSolution blockingQueueSolution = new BlockingQueueSolution();
        blockingQueueSolution.test();
    }
}