多线程之死锁问题

死锁的代码:

package com.qiu.syn;
//死锁:多个线程互相抱着对方需要的资源,然后形成僵持
public class DeadLock {
    public static void main(String[] args) {
        Makeup g1 = new Makeup(0, "我");
        Makeup g2 = new Makeup(1, "你");

​        g1.start();
​        g2.start();
​    }
}

//口红
class Lipstick{

}
//镜子
class Mirror{

}
class Makeup extends Thread{
    //需要的资源只有一份,用static来保证只有一份
    static Lipstick lipstick= new Lipstick();
    static Mirror mirror= new Mirror();

​    int choice;//选择
​    String girlName;//使用化妆品的人
​    Makeup(int choice,String girlName){
​        this.choice=choice;
​        this.girlName= girlName;
​    }
​    @Override
​    public void run() {
​    //化妆
​        try {
​            makeup();
​        } catch (InterruptedException e) {
​            e.printStackTrace();
​        }
​    }
​    //化妆,互相持有对方的锁,就是需要拿到对方的资源
​    private void makeup() throws InterruptedException {
​        if (choice == 0) {
​                synchronized (lipstick) {//获得口红的锁
​                System.out.println(this.girlName + "获得口红的锁");
​                Thread.sleep(1000);
​                synchronized (mirror) {//一秒钟后想获得镜子的锁
​                    System.out.println(this.girlName + "获得镜子的锁");
​                }
​            }
​        } else {
​                synchronized (mirror) {//一秒钟后想获得镜子的锁
​                System.out.println(this.girlName + "获得镜子的锁");
​                Thread.sleep(2000);
​                synchronized (lipstick) {//获得口红的锁
​                    System.out.println(this.girlName + "获得口红的锁");

​                }
​            }
​        }
​    }
}

改进死锁问题:

private void makeup() throws InterruptedException {
    if (choice == 0) {
            synchronized (lipstick) {//获得口红的锁
            System.out.println(this.girlName + "获得口红的锁");
            Thread.sleep(1000);
            }synchronized (mirror) {//一秒钟后想获得镜子的锁
                    System.out.println(this.girlName + "获得镜子的锁");
        }
    } else {
            synchronized (mirror) {//一秒钟后想获得镜子的锁
            System.out.println(this.girlName + "获得镜子的锁");
            Thread.sleep(2000);
            }synchronized (lipstick) {//获得口红的锁
                    System.out.println(this.girlName + "获得口红的锁");
        }
    }
}