2

本文主要简介一下TransferQueue。

TransferQueue

TransferQueue(java7引入)继承了BlockingQueue(BlockingQueue又继承了Queue)并扩展了一些新方法。生产者会一直阻塞直到所添加到队列的元素被某一个消费者所消费(不仅仅是添加到队列里就完事)。

LinkedTransferQueue

LinkedTransferQueue实际上是ConcurrentLinkedQueue、SynchronousQueue(公平模式)和LinkedBlockingQueue的超集。而且LinkedTransferQueue更好用,因为它不仅仅综合了这几个类的功能,同时也提供了更高效的实现。

对比SynchronousQueue

SynchronousQueue使用两个队列(一个用于正在等待的生产者、另一个用于正在等待的消费者)和一个用来保护两个队列的锁。而LinkedTransferQueue使用CAS操作实现一个非阻塞的方法,这是避免序列化处理任务的关键。

使用场景

当我们不想生产者过度生产消息时,TransferQueue可能非常有用,可避免发生OutOfMemory错误。在这样的设计中,消费者的消费能力将决定生产者产生消息的速度。

实例

public class LinkedTransferQueueDemo {
    static LinkedTransferQueue<String> lnkTransQueue = new LinkedTransferQueue<String>();
    public static void main(String[] args) {
        ExecutorService exService = Executors.newFixedThreadPool(2);
        Producer producer = new LinkedTransferQueueDemo().new Producer();
        Consumer consumer = new LinkedTransferQueueDemo().new Consumer();
        exService.execute(producer);
        exService.execute(consumer);
        exService.shutdown();
    }
    class Producer implements Runnable{
        @Override
        public void run() {
            for(int i=0;i<3;i++){
                try {
                    System.out.println("Producer is waiting to transfer...");
                    lnkTransQueue.transfer("A"+i);
                    System.out.println("producer transfered element: A"+i);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    class Consumer implements Runnable{
        @Override
        public void run() {
            for(int i=0;i<3;i++){
                try {
                    System.out.println("Consumer is waiting to take element...");
                    String s= lnkTransQueue.take();
                    System.out.println("Consumer received Element: "+s);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

输出

Producer is waiting to transfer...
Consumer is waiting to take element...
producer transfered element: A0
Producer is waiting to transfer...
Consumer received Element: A0
Consumer is waiting to take element...
producer transfered element: A1
Producer is waiting to transfer...
Consumer received Element: A1
Consumer is waiting to take element...
Consumer received Element: A2
producer transfered element: A2

doc


codecraft
11.9k 声望2k 粉丝

当一个代码的工匠回首往事时,不因虚度年华而悔恨,也不因碌碌无为而羞愧,这样,当他老的时候,可以很自豪告诉世人,我曾经将代码注入生命去打造互联网的浪潮之巅,那是个很疯狂的时代,我在一波波的浪潮上留下...