一、synchronized 加锁版

• 筷子

public class Chopstick {
    private String name;

    public Chopstick(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Chopstick{" +
                "name='" + name + '\'' +
                '}';
    }
}

• 哲学家

import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;


public class Philosopher extends Thread {
    final Chopstick left;
    final Chopstick right;

    public Philosopher(String name, Chopstick left, Chopstick right) {
        super(name);
        this.left = left;
        this.right = right;
    }

    @Override
    public void run() {
        while (true) {
            synchronized (left) {
                synchronized (right) {
                    eat();
                }
            }
            fight();
        }
    }

    public void eat(){
        System.out.println(this.getName()+":吃饭");
        try {
            TimeUnit.MICROSECONDS.sleep(ThreadLocalRandom.current().nextInt(100));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    public void fight(){
        System.out.println(this.getName()+":摔跤");
        try {
            TimeUnit.MICROSECONDS.sleep(ThreadLocalRandom.current().nextInt(100));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

• 测试类

public class PhilosopherTest1 {
    public static void main(String[] args) {
        Chopstick a = new Chopstick("a");
        Chopstick b = new Chopstick("b");
        Chopstick c = new Chopstick("c");
        Chopstick d = new Chopstick("d");
        Chopstick e = new Chopstick("e");

        new Philosopher("Banana", a, b).start();
        new Philosopher("Rossett", b, c).start();
        new Philosopher("Van", c, d).start();
        new Philosopher("Billy", d, e).start();
        new Philosopher("Biollante", e, a).start();
        //new Philosopher("Biollante", a, e).start();//改变顺序打破死锁
    }
}

二、ReentranLock谦让版。

• 筷子

import java.util.concurrent.locks.ReentrantLock;

public class Chopstick2 extends ReentrantLock {
    private final String name;

    public Chopstick2(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return name;
    }
}

• 哲学家

import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.TimeUnit;

public class Philosopher2 extends Thread {
    Chopstick2 left;
    Chopstick2 right;

    public Philosopher2(String name, Chopstick2 left, Chopstick2 right) {
        super(name);
        this.left = left;
        this.right = right;
    }

    @Override
    public void run() {
        while (true) {
            if (left.tryLock()) {
                try {
                    if (right.tryLock()) {
                        try {
                            eat();
                        }finally {
                            right.unlock();
                        }
                    }
                }finally {
                    left.unlock();
                }
            }
            fight();
        }
    }

    public void eat(){
        System.out.println(this.getName()+":吃饭");
        try {
            TimeUnit.MICROSECONDS.sleep(ThreadLocalRandom.current().nextInt(100));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    public void fight(){
        System.out.println(this.getName()+":摔跤");
        try {
            TimeUnit.MICROSECONDS.sleep(ThreadLocalRandom.current().nextInt(100));
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

• 测试类

public class PhilosopherTest2 {
    public static void main(String[] args) {
        Chopstick2 a = new Chopstick2("a");
        Chopstick2 b = new Chopstick2("b");
        Chopstick2 c = new Chopstick2("c");
        Chopstick2 d = new Chopstick2("d");
        Chopstick2 e = new Chopstick2("e");

        new Philosopher2("Banana", a, b).start();
        new Philosopher2("Rossett", b, c).start();
        new Philosopher2("Van", c, d).start();
        new Philosopher2("Billy", d, e).start();
        new Philosopher2("Biollante", a, b).start();
    }
}