Java 生产者消费者实现

Java

《Java 编程思想》中，使用 厨师-服务员 来表示：生产者、消费者。

思路

chef 在 有 meal 的时候，会释放锁；在制作 meal 时，会获取 waitPerson 的锁，制作完 meal 后，唤醒所有的 waitPerson；

waitPerson 在 没有 meal 的时候，会释放锁；在消费 meal 后，会将 meal 置为 null，操作期间需要获得 chef 的锁。

实现

public class Restaurant {
    Meal meal;
    ExecutorService exec = Executors.newCachedThreadPool();
    WaitPerson waitPerson = new WaitPerson(this);
    Chef chef = new Chef(this);
    public Restaurant() {
        exec.execute(chef);
        exec.execute(waitPerson);
    }
    public static void main(String[] args) {
        new Restaurant();
    }
}

public class Meal {
    private final int orderNum;
    public Meal(int orderNum) {
        this.orderNum = orderNum;
    }
    @Override
    public String toString() {
        return "Meal " + orderNum;
    }
}

public class Chef implements Runnable{
    private int count = 0;
    private Restaurant restaurant;
    public Chef(Restaurant restaurant) {
        this.restaurant = restaurant;
    }
    @Override
    public void run() {
        try {
            while (!Thread.interrupted()) { // shutdownNow 后，会退出循环
                synchronized (this) {
                    // 如果有 meal，则释放锁，等待
                    while (restaurant.meal != null) {
                        wait();
                    }
                }
                if (++ count == 10) {
                    System.out.println("Out of 10");
                    restaurant.exec.shutdownNow();
                }
                synchronized (restaurant.waitPerson) {
                    restaurant.meal = new Meal(count);
                    restaurant.waitPerson.notifyAll();
                }
                TimeUnit.SECONDS.sleep(1);
            }
        } catch (Exception e) {
            System.out.println("Chef interrupted");
        }
    }
}

public class WaitPerson implements Runnable{
    private Restaurant restaurant;
    public WaitPerson(Restaurant restaurant) {
        this.restaurant = restaurant;
    }
    @Override
    public void 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;
                    restaurant.chef.notifyAll();
                }
            }
        } catch (Exception e) {
            System.out.println("WaitPerson interrupted");
        }
    }
}