Question

我的代码如下所示，它有两个Runnable类：Cook（生产者）和Waiter（消费者）。

当饭菜数少于5时，库克会去上班，
当用餐人数超过0时服务员会去上班。

它运行正常但无法停止我在代码的末尾添加了exec.shutdown()，但没有任何反应如果我将其替换为exec.shutdownNow()，则在尝试睡眠时会抛出2 InterruptedException。之后，该程序仍在运行。

如何阻止它？
我的代码是否是“模拟”ProducerConsumer情况的正确方法？（这是我第一次尝试并发）

package com.imooc;

import java.util.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

class Meal {
    private final int id;

    Meal(int id) {
        this.id = id;
    }

    public String toString() {
        return "Meal: " + id;
    }
}

class Cook implements Runnable {
    private LinkedList<Meal> mealList;
    private static int count;

    Cook(LinkedList<Meal> mealList) {
        this.mealList = mealList;
    }

    public void run() {
        while (!Thread.interrupted()) {
            synchronized (mealList) {
                while (mealList.size() < 5) {
                    System.out.print("Cook is cooking meal：");
                    System.out.println(++count);
                    mealList.add(new Meal(count));
                    try {
                        TimeUnit.MILLISECONDS.sleep(200);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
                mealList.notifyAll();
                while (mealList.size() == 5) {
                    System.out.println("Cook is waiting");
                    try {
                        mealList.wait();
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        }
        System.out.println("Cook is off-duty");
    }
}

class Waiter implements Runnable {
    private LinkedList<Meal> mealList;

    Waiter(LinkedList<Meal> mealList) {
        this.mealList = mealList;
    }

    public void run() {
        while (!Thread.interrupted()) {
            synchronized (mealList) {
                while (mealList.size() > 0) {
                    System.out.println("Waiter is taking this meal:" + mealList.getLast());
                    mealList.removeLast();
                    try {
                        TimeUnit.MILLISECONDS.sleep(200);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
                mealList.notifyAll();
                while (mealList.size() == 0) {
                    System.out.println("Waiter is waiting");
                    try {
                        mealList.wait();
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
            }
        }
        System.out.println("Waiter is off-duty");
    }
}

public class Manager {

    public static void main(String args[]) {
        LinkedList<Meal> mealList = new LinkedList<Meal>();
        ExecutorService exec = Executors.newCachedThreadPool();
        exec.execute(new Waiter(mealList));
        exec.execute(new Cook(mealList));
        exec.execute(new Waiter(mealList));
        exec.execute(new Waiter(mealList));
        exec.execute(new Cook(mealList));
        exec.shutdown();
    }

}

此处输出截图：

Answer 1

首先，exec.shutdown()仅表示执行者不接受新任务。如果您要取消现有任务，则需要致电exec.shutdownNow()。

其次，捕获InterruptedException会重置线程的中断标记，而while(!Thread.interrupted())将无法按预期工作。

最后，即使你在捕获异常后用Thread.currentThread().interrupt()重置了中断的标志，各种条件（例如while (mealList.size() < 5)）可能仍然是假的，你将永远循环而不会到达你所在的行检查是否中断。

如何在ProducerConsumer情况下停止Java线程？

1 个答案: