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java实现生产者消费者问题
引言
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段内共用同一个存储空间，如下图所示，生产者向空间里存放数据，而消费者取用数据，如果不加以协调可能会出现以下情况：
生产者消费者图
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。
JAVA解决线程模型的三种方式
1、wait()和notify()
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.wait(); } Object newOb = new Object(); if (storeHouse.add(newOb)) { System.out.println("Producer put a Object to storeHouse"); Thread.sleep((long) (Math.random() * 3000)); storeHouse.notify(); } } 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.wait(); } storeHouse.removeLast(); System.out.println("Comsumer get a Object from storeHouse"); Thread.sleep((long) (Math.random() * 3000)); storeHouse.notify(); } catch (InterruptedException ie) { System.out.println("Consumer is interrupted"); } } } } } public static void main(String[] args) throws Exception { ProducerConsumer pc = new ProducerConsumer(); pc.start(); }}
2、await()和signal()，即线程锁的方式
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(); } } } }}
3、阻塞队列的方式
import java.util.concurrent.*;public class ProducerConsumer { // 建立一个阻塞队列 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!"); } // } } } }}结论
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，线程同步的操作交由LinkedBlockingQueue全权处理。
java实现生产者消费者问题
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