使用java Condition构建生产者消费者

来源：互联网发布：python 最优化工具包编辑：程序博客网时间：2024/05/12 05:21

1.Condition介绍

在上一篇文章中曾经提到对象的wait和notify方法，condition类其实就是这种方法的一种替代性产物。
Condition对象是同Lock结合使用，由Lock进行创建，并且condition.await的调用者必须获取lock，在await时该线程自动释放锁，当其被其他线程signal之后再重新获取锁，这同上一篇博客中提到的sychronized的用法类似。

2. 基于Condition的生产者消费者程序

（貌似ArrayBlockingQueue）这里使用notFull和notEmpty表示链表中元素有无的一个条件，具体代码如下：

package concurrency;/** * Created by wangxiaoyi on 15/11/18. */import java.util.LinkedList;import java.util.List;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;public class ProducerAndConsumer2 {    private List<Integer> data = new LinkedList<>();    private static final int MAX_DATA_LEN = 10;    private Lock lock = new ReentrantLock();    private Condition notEmpty = lock.newCondition();// 非空条件    private Condition notFull = lock.newCondition();// 非满条件    class Producer implements Runnable {        private int pid = 0;        public Producer(int pid){            this.pid = pid;        }        public void run() {            try {                while (!Thread.currentThread().isInterrupted()) {                    lock.lock();                    while (data.size() >= MAX_DATA_LEN) {                        System.out.println("Producer" + pid + " waiting ! size : " + data.size());                        notFull.await(); // 等待notFull.signal唤醒                    }                    try{                        data.add(pid);                        notEmpty.signal(); // 唤醒notEmpty.await()线程                        System.out.println("Producer" + pid + " add " + pid + " size: " + data.size());                    }finally {                        lock.unlock();                    }                    Thread.sleep(500);                }            } catch (InterruptedException ie) {                ie.printStackTrace();            }        }    }    class Consumer implements Runnable{        private int cid = 0;        public Consumer(int cid){            this.cid = cid;        }        public void run(){            try {                while (!Thread.currentThread().isInterrupted()) {                    lock.lock();                    while (data.isEmpty()) {                        System.out.println("Consumer" + cid + " waiting, data size : " + data.size());                        notEmpty.await();                    }                    try{                        int pid = data.remove(0);                        notFull.signal();                        System.out.println("Consumer" + cid + " consuming data " + pid +" data size : " + data.size());                    }finally {                        lock.unlock();                    }                    Thread.sleep(500);                }            }catch (InterruptedException ie){                ie.printStackTrace();            }        }    }    public void start(){        ExecutorService executor = Executors.newCachedThreadPool();        for(int i = 0; i < 5; ++ i){            executor.submit(new Producer(i));            executor.submit(new Consumer(i));        }        try {            Thread.sleep(10*1000);        } catch (InterruptedException e) {            e.printStackTrace();        }        executor.shutdownNow();    }    public static void main(String []args){        new ProducerAndConsumer2().start();    }}

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