java实现生产者消费者问题

引言 java

  生产者和消费者问题是线程模型中的经典问题:生产者和消费者在同一时间内共用同一个存储空间,以下图所示,生产者向空间里存放数据,而消费者取用数据,若是不加以协调可能会出现如下状况: dom

生产者消费者图 spa

  存储空间已满,而生产者占用着它,消费者等着生产者让出空间从而去除产品,生产者等着消费者消费产品,从而向空间中添加产品。互相等待,从而发生死锁。 线程

JAVA解决线程模型的三种方式 code

  一、wait()和notify() 对象

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import java.util.LinkedList; public class ProducerConsumer { private LinkedList<Object> storeHouse = new LinkedList<Object>(); private int MAX = 10; public ProducerConsumer() { } public void start() { new Producer().start(); new Comsumer().start(); } class Producer extends Thread { public void run() { while (true) { synchronized (storeHouse) { try { while (storeHouse.size() == MAX) { System.out.println("storeHouse is full , please wait"); storeHouse.await(); } Object newOb = new Object(); if (storeHouse.add(newOb)) { System.out.println("Producer put a Object to storeHouse"); Thread.sleep((long) (Math.random() * 3000)); storeHouse.signal(); } } catch (InterruptedException ie) { System.out.println("producer is interrupted!"); } } } } } class Comsumer extends Thread { public void run() { while (true) { synchronized (storeHouse) { try { while (storeHouse.size() == 0) { System.out.println("storeHouse is empty , please wait"); storeHouse.await(); } storeHouse.removeLast(); System.out.println("Comsumer get  a Object from storeHouse"); Thread.sleep((long) (Math.random() * 3000)); storeHouse.signal(); } catch (InterruptedException ie) { System.out.println("Consumer is interrupted"); } } } } } public static void main(String[] args) throws Exception { ProducerConsumer pc = new ProducerConsumer(); pc.start(); } }
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  二、await()和signal(),即线程锁的方式 队列

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package sort; import java.util.LinkedList; import java.util.concurrent.locks.Condition; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; public class ProducerConsumer { private LinkedList<Object> myList = new LinkedList<Object>(); private int MAX = 10; private final Lock lock = new ReentrantLock(); private final Condition full = lock.newCondition(); private final Condition empty = lock.newCondition(); public ProducerConsumer() { } public void start() { new Producer().start(); new Consumer().start(); } public static void main(String[] args) throws Exception { ProducerConsumer s2 = new ProducerConsumer(); s2.start(); } class Producer extends Thread { public void run() { while (true) { lock.lock(); try { while (myList.size() == MAX) { System.out.println("warning: it's full!"); full.await(); } Object o = new Object(); if (myList.add(o)) { System.out.println("Producer: " + o); empty.signal(); } } catch (InterruptedException ie) { System.out.println("producer is interrupted!"); } finally { lock.unlock(); } } } } class Consumer extends Thread { public void run() { while (true) { lock.lock(); try { while (myList.size() == 0) { System.out.println("warning: it's empty!"); empty.await(); } Object o = myList.removeLast(); System.out.println("Consumer: " + o); full.signal(); } catch (InterruptedException ie) { System.out.println("consumer is interrupted!"); } finally { lock.unlock(); } } } } }
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  三、阻塞队列的方式 rem

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import java.util.concurrent.*; public class ProducerConsumer { // 创建一个阻塞队列 private LinkedBlockingQueue<Object> queue = new LinkedBlockingQueue<Object>(10); public ProducerConsumer() { } public void start() { new Producer().start(); new Consumer().start(); } public static void main(String[] args) throws Exception { ProducerConsumer s3 = new ProducerConsumer(); s3.start(); } class Producer extends Thread { public void run() { while (true) { try { Object o = new Object(); // 取出一个对象  queue.put(o); System.out.println("Producer: " + o); } catch (InterruptedException e) { System.out.println("producer is interrupted!"); } // }  } } } class Consumer extends Thread { public void run() { while (true) { try { // 取出一个对象 Object o = queue.take(); System.out.println("Consumer: " + o); } catch (InterruptedException e) { System.out.println("producer is interrupted!"); } // }  } } } }
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结论 get

  三种方式原理一致,都是对独占空间加锁,阻塞和唤醒线程,第一种方式比较传统,第三种方式最简单,只需存储和取用,线程同步的操做交由LinkedBlockingQueue全权处理。 同步

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