生产者-消费者模式

• 传递消息的实体类

public class Message {
    private String data;

    public Message(String data) {
        this.data = data;
    }

    public String getData() {
        return data;
    }
}

• 维护消息的队列

public class MessageQueue {

    private final LinkedList<Message> queue;

    private final static int DEFAULT_MAX_LIMIT = 100;

    private final int limit;

    public MessageQueue() {
        this(DEFAULT_MAX_LIMIT);
    }

    public MessageQueue(final int limit) {
        this.limit = limit;
        this.queue = new LinkedList<>();
    }

    public void put(final Message message) throws InterruptedException {
        synchronized (queue) {
            while (queue.size() > limit) {
                queue.wait();
            }

            queue.addLast(message);
            queue.notifyAll();
        }
    }

    public Message take() throws InterruptedException {
        synchronized (queue) {
            while (queue.isEmpty()) {
                queue.wait();
            }

            Message message = queue.removeFirst();
            queue.notifyAll();
            return message;
        }
    }

    public int getMaxLimit() {
        return this.limit;
    }

    public int getMessageSize() {
        synchronized (queue) {
            return queue.size();
        }
    }
}

• 生产者线程

public class ProducerThread extends Thread {

    private final MessageQueue messageQueue;

    private final static Random random = new Random(System.currentTimeMillis());

    private final static AtomicInteger counter = new AtomicInteger(0);

    public ProducerThread(MessageQueue messageQueue, int seq) {
        super("PRODUCER-" + seq);
        this.messageQueue = messageQueue;
    }

    @Override
    public void run() {
        while (true) {
            try {
                Message message = new Message("Message-" + counter.getAndIncrement());
                messageQueue.put(message);
                System.out.println(Thread.currentThread().getName() + " put message " + message.getData());
                Thread.sleep(random.nextInt(1000));
            } catch (InterruptedException e) {
                break;
            }
        }
    }

• 消费者线程

public class ConsumerThread extends Thread {

    private final MessageQueue messageQueue;

    private final static Random random = new Random(System.currentTimeMillis());

    public ConsumerThread(MessageQueue messageQueue, int seq) {
        super("Consumer-" + seq);
        this.messageQueue = messageQueue;
    }

    @Override
    public void run() {
        while (true) {
            try {
                Message message = messageQueue.take();
                System.out.println(Thread.currentThread().getName() + " take a message " + message.getData());
                Thread.sleep(random.nextInt(1000));
            } catch (InterruptedException e) {
                break;
            }
        }
    }
}

• 运行类

public class ProducerAndConsumerClient {

    public static void main(String[] args) {
        final MessageQueue messageQueue = new MessageQueue();
        new ProducerThread(messageQueue, 1).start();
        new ProducerThread(messageQueue, 2).start();
        new ProducerThread(messageQueue, 3).start();
        new ConsumerThread(messageQueue, 1).start();
        new ConsumerThread(messageQueue, 2).start();
    }
}