java 厨师,顾客,订餐的多线程示例程序

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厨师,顾客,订餐的多线程示例程序

1)wait方法要在一个循环中

public void waitForChef() throws InterruptedException { while (readyFlag) wait(); }

2)由于厨师线程有多个,顾客有多个,所以要用notifyAll方法,而不是notify,因为notify很容易就产生死锁

3)TimeUnit.MILLISECONDS.sleep(200); 用于降低程序的运行速度,用于示例

while (!Thread.interrupted()) { <span style="font-family: Arial, Helvetica, sans-serif;">}</span>

用于检测异常,异常可能发生在sleep()方法中,也可能发生在wait方法中,也可能在while体中的其他部分,这时候下次执行while便会退出while循环,

由于

Thread.interrupted()

方法会清楚异常标识,所以最后

exec.shutdownNow();

执行时,有一部分线程的catch语句中的print语句并不会得到执行

5)条件检测和线程的主要任务执行都要放在synchronized块中

import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.TimeUnit;class Meal {private static int  count=0;    private final int orderNum=++count;    public String toString() {        return " Meal "+orderNum;    }    }class WaitPerson implements Runnable {    private Restaurant restaurant;    public WaitPerson( Restaurant restaurant) {        this.restaurant=restaurant;    }    public void run() {        try {        while (!Thread.interrupted()) {                synchronized(restaurant) {                restaurant.waitForEating();                    System.out.println("The WaitPerson "+Thread.currentThread().getId()+" has eaten " + restaurant.meal);                    restaurant.setReadyFlag(false);                    restaurant.notifyAll();                }        }        } catch(InterruptedException e) {        System.out.print("Exiting via interrupt in WaitPerson in thread-->"+ Thread.currentThread().getId());        }        System.out.print("Exiting in WaitPerson in thread-->"+ Thread.currentThread().getId());    }}class Chef implements Runnable {    private Restaurant restaurant;    public Chef( Restaurant restaurant) {        this.restaurant=restaurant;    }    public void run() {        try {        while (!Thread.interrupted()) {                synchronized(restaurant) {                 TimeUnit.MILLISECONDS.sleep(200);                restaurant.waitForChef();                restaurant.meal=new Meal();                    System.out.println("The Chef "+Thread.currentThread().getId()+" has made" + restaurant.meal);                    restaurant.setReadyFlag(true);                    restaurant.notifyAll();                }            }        } catch(InterruptedException e) {        System.out.print("Exiting via interrupt in Chef in thread-->"+ Thread.currentThread().getId());        }        System.out.print("Exiting in Chef in thread-->"+ Thread.currentThread().getId());    }}public class Restaurant {     private boolean readyFlag=false; //true 做好了, false代表没做好          public Meal meal=null;          public void setReadyFlag(boolean readyFlag) {this.readyFlag = readyFlag;}public void waitForChef() throws InterruptedException { while (readyFlag) wait(); } public void waitForEating() throws InterruptedException { while (readyFlag == false) wait(); }         public static void main(String[] args) throws Exception {        Restaurant restaurant=new Restaurant();    ExecutorService exec = Executors.newFixedThreadPool(20);for (int i = 0; i < 10; i++) {exec.execute(new Chef(restaurant));exec.execute(new WaitPerson(restaurant));}TimeUnit.SECONDS.sleep(10); // Run for a while...exec.shutdownNow(); // Interrupt all tasks    }}

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