哲學家就餐

import java.sql.Time;
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

public class 哲學家就餐 {
    public static void main(String[] args) {
        //線程池
        ExecutorService exec= Executors.newCachedThreadPool();
        int sum=5;
        //5個筷子
        Chopstick[] chopsticks=new Chopstick[sum];
        for (int i = 0; i <sum ; i++) {
            chopsticks[i]=new Chopstick(i);

        }
        //5個哲學家
        for (int i = 0; i < sum-1; i++) {
            exec.execute(new Philosopher(chopsticks[i],chopsticks[(i+1)%sum],i));
        }
        exec.execute(new Philosopher(chopsticks[0],chopsticks[sum-1],sum));
    }

}

//筷子類
class Chopstick{
    //筷子位置
    private int index;
    //狀態（有沒有被使用)
    private boolean isUsed=false;
    public Chopstick(int index){
        this.index=index;
    }
    //拿筷子
    public synchronized void take() throws InterruptedException {
        //如果筷子被使用了，就進行等待
        while (isUsed){
            wait();
        }
        System.out.println(this+"被使用...");
        isUsed=true;
    }
    //放筷子
    public synchronized void drop(){
        isUsed=false;
        System.out.println(this+"被放下");
        notifyAll();
    }

    @Override
    public String toString() {
        return "筷子["+index+"]";
    }
}

//哲學家
class Philosopher implements Runnable{
    private Chopstick left;
    private Chopstick right;
    //哲學家編號
    private int index;
    private Random rand=new Random();

    public Philosopher(Chopstick left,Chopstick right,int index){
        this.left=left;
        this.right=right;
        this.index=index;
    }

    @Override
    public void run() {
        while (!Thread.interrupted()){

            try {
                think();
                System.out.println(this+"想吃飯。。");
                eat();
            } catch (InterruptedException e) {
                System.out.println("InterruptedException..");
            }
        }
    }
    //思考
    private void think() throws InterruptedException {
        System.out.println(this+"思考");
        TimeUnit.MILLISECONDS.sleep(rand.nextInt(1)*100);
    }

    //吃飯
    private void eat() throws InterruptedException {
        left.take();
        right.take();
        System.out.println(this+"正在吃飯。。");
        TimeUnit.MILLISECONDS.sleep(rand.nextInt(2)*100);
        left.drop();
        right.drop();
    }
    @Override
    public String toString() {
        return "哲學家["+index+"]";
    }
}