Producer Consumer using BlockingQueue

Usage example, based on a typical producer-consumer scenario. Note that a BlockingQueue can safely be used with multiple producers and multiple consumers.

 class Producer implements Runnable {
   private final BlockingQueue queue;
   Producer(BlockingQueue q) { queue = q; }
   public void run() {
     try {
       while (true) { queue.put(produce()); }
     } catch (InterruptedException ex) { ... handle ...}
   }
   Object produce() { ... }
 }

 class Consumer implements Runnable {
   private final BlockingQueue queue;
   Consumer(BlockingQueue q) { queue = q; }
   public void run() {
     try {
       while (true) { consume(queue.take()); }
     } catch (InterruptedException ex) { ... handle ...}
   }
   void consume(Object x) { ... }
 }

 class Setup {
   void main() {
     BlockingQueue q = new ArrayBlockingQueue();
     Producer p = new Producer(q);
     Consumer c1 = new Consumer(q);
     Consumer c2 = new Consumer(q);
     new Thread(p).start();
     new Thread(c1).start();
     new Thread(c2).start();
   }
 }

Memory consistency effects: As with other concurrent collections, actions in a thread prior to placing an object into a BlockingQueue happen-before actions subsequent to the access or removal of that element from theBlockingQueue in another thread.

BlockingQueue是Java Collection框架的一个接口，下面有很多实现类，包括：

ArrayBlockingQueue, (这个要自己会实现)

DelayQueue,  

LinkedBlockingQueue, 

PriorityBlockingQueue

不用BlockingQueue实现的话，可以这么做：

public class Drop {
    // Message sent from producer
    // to consumer.
    private String message;
    // True if consumer should wait
    // for producer to send message,
    // false if producer should wait for
    // consumer to retrieve message.
    private boolean empty = true;

    public synchronized String take() {
        // Wait until message is
        // available.
        while (empty) {
            try {
                wait();
            } catch (InterruptedException e) {}
        }
        // Toggle status.
        empty = true;
        // Notify producer that
        // status has changed.
        notifyAll();
        return message;
    }

    public synchronized void put(String message) {
        // Wait until message has
        // been retrieved.
        while (!empty) {
            try { 
                wait();
            } catch (InterruptedException e) {}
        }
        // Toggle status.
        empty = false;
        // Store message.
        this.message = message;
        // Notify consumer that status
        // has changed.
        notifyAll();
    }
}


public class Producer implements Runnable {
    private Drop drop;

    public Producer(Drop drop) {
        this.drop = drop;
    }

    public void run() {
        String importantInfo[] = {
            "Mares eat oats",
            "Does eat oats",
            "Little lambs eat ivy",
            "A kid will eat ivy too"
        };
        Random random = new Random();

        for (int i = 0;
             i < importantInfo.length;
             i++) {
            drop.put(importantInfo[i]);
            try {
                Thread.sleep(random.nextInt(5000));
            } catch (InterruptedException e) {}
        }
        drop.put("DONE");
    }
}

public class Consumer implements Runnable {  
    private Drop drop;  
  
    public Consumer(Drop drop) {  
        this.drop = drop;  
    }  
  
    public void run() {  
        Random random = new Random();  
        for (String message = drop.take();  
             ! message.equals("DONE");  
             message = drop.take()) {  
            System.out.format("MESSAGE RECEIVED: %s%n", message);  
            try {  
                Thread.sleep(random.nextInt(5000));  
            } catch (InterruptedException e) {}  
        }  
    }  
}

public class ProducerConsumerExample {  
    public static void main(String[] args) {  
        Drop drop = new Drop();  
        (new Thread(new Producer(drop))).start();  
        (new Thread(new Consumer(drop))).start();  
    }  
}

以上代码来自：

http://blog.csdn.net/shymi1991/article/details/39267821