生产者与消费者模式 实例

??? 如果没记错在gof的23种设计模式里面并没有涉及到生产者与消费者模式，记得很就以前有个面试官叫我讲解下生产者与消费者模式，当时我就闷了，我就一直不停的在记忆中从23种模式搜索，结果无论如何都是想不起来，所以很尴尬了。

??? 好吧，废话不多说

??? 有这样一个饭店，他有一个厨师和一个服务员。这个服务员必须等待厨师准备好膳食。当厨师准备好时，他会通知服务员，之后服务员上菜，然后返回继续等待。这是一个协作的示例：两个任务必须在膳食被生产和消费时进行握手，厨师是生产者，服务员是消费者，而系统必须有序的方式关闭。

??? 以下是代码，比较简单的一个小例子。

??? Meal.java

package com.cs.model;/*** 膳食* @author chinasoft**/publicclass Meal {privatefinalintorderNum;public Meal(int orderNum) {this.orderNum = orderNum;}@Overridepublic String toString() {return"meal" + orderNum;}}

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Chef .java

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package com.cs.person;import java.util.concurrent.TimeUnit;import com.cs.model.Meal;import com.cs.run.Restaurant;/*** 厨师* @author chinasoft**/publicclass Chef implements Runnable {private Restaurant restaurant;privateintcount = 0;public Chef(Restaurant restaurant) {this.restaurant = restaurant;}@Overridepublicvoid run() {try {while (!Thread.interrupted()) {synchronized (this) {while (restaurant.meal != null) {System.out.println("Chef wait");wait();}}if (++count == 10) {System.out.println("out food is closing");restaurant.exec.shutdownNow();}System.out.println("Order up!");synchronized (restaurant.waitPerson) {restaurant.meal = new Meal(count);restaurant.waitPerson.notifyAll();}//由于生产者提供的较快可以让他速度慢点，以免出现等待现象TimeUnit.MICROSECONDS.sleep(100);}} catch (InterruptedException e) {System.out.println("Chef interrupted");}}}

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WaitPerson.java

package com.cs.person;import com.cs.run.Restaurant;/*** 服务员* @author chinasoft**/publicclass WaitPerson implements Runnable {private Restaurant restaurant;public WaitPerson(Restaurant restaurant) {this.restaurant = restaurant;}@Overridepublicvoid run() {try {while (!Thread.interrupted()) {synchronized (this) {while (restaurant.meal == null)wait();}System.out.println("WaitPerson got" + restaurant.meal);synchronized (restaurant.chef) {restaurant.meal = null;//这里理论上是调用notify（），但是，在更复杂的情况下，可能有多个任务给对象上锁//而你不知道是哪个任务，所以调用notifyAll更加安全restaurant.chef.notifyAll();}}} catch (InterruptedException e) {System.out.println("waitPerson interrupt");}}}

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Restaurant.java

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package com.cs.run;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import com.cs.model.Meal;import com.cs.person.Chef;import com.cs.person.WaitPerson;/*** 餐厅* @author chinasoft**/publicclass Restaurant {public Meal meal;public Chef chef = new Chef(this);public WaitPerson waitPerson = new WaitPerson(this);/** 执行线程池*/public ExecutorService exec = Executors.newCachedThreadPool();public Restaurant() {exec.execute(chef);exec.execute(waitPerson);}publicstaticvoid main(String[] args) {new Restaurant();}}

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