Restaurant

/*
    Jatin Thakur
    coderbots.blogspot.com
*/

import java.util.concurrent.*;
import java.util.concurrent.locks.*;

class BusBoy implements Runnable {

    Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition();

    Restaurant restaurant;

    BusBoy(Restaurant r) {
        restaurant = r;
    }

    public void run() {
        try {
            while (!Thread.interrupted()) {

                lock.lock();
                try {
                    condition.await();
                    System.out.println("BusBoy is Cleaning up!\n");
                } finally {
                    lock.unlock();
                }
            }
        } catch (InterruptedException e) {
            System.out.println("BusBoy interrupted!");
        }
    }

}

class Meal {

    private final int orderNum;
    volatile int cleanUp = 0;

    public Meal(int orderNum) {
        this.orderNum = orderNum;
    }

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

class WaitPerson implements Runnable {

    Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition();

    private Restaurant restaurant;

    public WaitPerson(Restaurant r) {
        restaurant = r;
    }

    public void run() {
        try {
            while (!Thread.interrupted()) {
                lock.lock();
                try {
                    while (restaurant.meal == null) {
                        condition.await(); //... for the chef to produce a meal
                    }
                } finally {
                    lock.unlock();
                }
                System.out.println("Waitperson got " + restaurant.meal);

                restaurant.chef.lock.lock();
                try {
                    restaurant.meal = null;
                    System.out.println("Meal taken by the waitperson!");
                    restaurant.chef.condition.signalAll(); //Ready for another
                } finally {
                    restaurant.chef.lock.unlock();
                }

                try {
                    restaurant.boy.lock.lock();
                    System.out.println("Notifying BusBoy to cleanup...");
                    restaurant.boy.condition.signalAll();
                } finally {
                    restaurant.boy.lock.unlock();
                }
            }
        } catch (InterruptedException e) {
            System.out.println("WaitPerson interrupted!");
        }
    }
}

class Chef implements Runnable {

    Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition();
    private Restaurant restaurant;
    private int count = 0;

    public Chef(Restaurant r) {
        restaurant = r;
    }

    public void run() {
        try {
            while (!Thread.interrupted()) {
                lock.lock();
                try {

                    while (restaurant.meal != null) {
                        condition.await();//... for the meal to be taken
                    }
                } finally {
                    lock.unlock();
                }

                if (++count == 10) {
                    System.out.println("Out of food, closing");
                    restaurant.exec.shutdownNow();
                    return;
                }
                System.out.println("Order up!");
                restaurant.waitPerson.lock.lock();
                try {
                    restaurant.meal = new Meal(count);
                    restaurant.waitPerson.condition.signalAll();
                } finally {
                    restaurant.waitPerson.lock.unlock();
                }
                TimeUnit.MILLISECONDS.sleep(100);
            }
        } catch (InterruptedException e) {
            System.out.println("Chef interrupted!");
        }
    }
}

public class Restaurant {

    Meal meal;
    ExecutorService exec = Executors.newCachedThreadPool();
    WaitPerson waitPerson = new WaitPerson(this);
    Chef chef = new Chef(this);
    BusBoy boy = new BusBoy(this);

    public Restaurant() {
        exec.execute(chef);
        exec.execute(waitPerson);
        exec.execute(boy);
    }

    public static void main(String[] args) {
        new Restaurant();
    }

}