手写一个死锁

手写一个死锁、死锁满足的条件

1、至少有两个线程互相争夺共享资源

2、至少有两把锁两个线程分别持有锁

两个线程各自持有一把锁并且企图获取到对方的正在持有的锁

package demos;

import java.util.concurrent.TimeUnit;

/**
 * 写一个死锁第一种写法
 */
public class DeadLock {
    public static void main(String[] args) {
        String a = "a";
        String b = "b";

        new Thread(new Resource(a,b),"ThreadA").start();
        new Thread(new Resource(b,a),"ThreadB").start();
    }
}

class Resource implements Runnable{

    String a;
    String b;

    public Resource(String a,String b){
        this.a = a;
        this.b = b;
    }

    @Override
    public void run() {
        synchronized (a){
            System.out.println(Thread.currentThread().getName());
            try {
                TimeUnit.SECONDS.sleep(2L);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            synchronized (b){
                System.out.println(Thread.currentThread().getName());
            }
        }
    }
}

package demos;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * 写一个死锁第二种写法用lock
 */
public class DeadLock1 {
    public static void main(String[] args) {
        Lock lock1 = new ReentrantLock();
        Lock lock2 = new ReentrantLock();

        new Thread(new Resource1(lock1,lock2),"A").start();
        new Thread(new Resource1(lock2,lock1),"B").start();

    }
}
class Resource1 implements Runnable{

    Lock lock1;
    Lock lock2;

    public Resource1(Lock lock1,Lock lock2){
        this.lock1 = lock1;
        this.lock2 = lock2;
    }

    @Override
    public void run() {
        lock1.lock();
        try{

            System.out.println(Thread.currentThread().getName());
            Thread.sleep(2);
            lock2.lock();
            try{
                System.out.println(Thread.currentThread().getName());
            }finally {
                lock2.unlock();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            lock1.unlock();
        }
    }
}