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1.死锁代码

//死锁：多个线程互相抱着对方需要的资源，然后形成僵局public class DeadLock {
       public static void main(String[] args) {
           Makeup girl1 = new Makeup(0,"灰姑娘");        Makeup girl2 = new Makeup(1,"白雪公主");        girl1.start();        girl2.start();    }}//口红class Lipstick{
   }//镜子class Mirror{
   }class Makeup extends Thread{
       //需要的资源只能有一份，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    public Makeup(int choice, String girlName) {
           this.choice = choice;        this.girlName = girlName;    }    @Override    public void run(){
           try {
               makeup();//化妆        } catch (InterruptedException e) {
               e.printStackTrace();        }    }    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                    System.out.println(this.girlName+"获取镜子的锁");                }            }        }else {
               synchronized (mirror){
   //获得镜子的锁                System.out.println(this.girlName+"获得镜子的锁");                Thread.sleep(2000);                synchronized (lipstick){
   //两秒钟后，想获得口红                    System.out.println(this.girlName+"获取口红的锁");                }            }        }    }}

关键代码

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                    System.out.println(this.girlName+"获取镜子的锁");                }            }        }else {
               synchronized (mirror){
   //获得镜子的锁                System.out.println(this.girlName+"获得镜子的锁");                Thread.sleep(2000);                synchronized (lipstick){
   //两秒钟后，想获得口红                    System.out.println(this.girlName+"获取口红的锁");                }            }        }    }

上述代码解析，当一个线程A锁住口红不放，同时想拿镜子

2.解决后的代码

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                System.out.println(this.girlName+"获取镜子的锁");            }        }else {
               synchronized (mirror){
   //获得镜子的锁                System.out.println(this.girlName+"获得镜子的锁");                Thread.sleep(2000);            }            synchronized (lipstick){
   //两秒钟后，想获得口红                System.out.println(this.girlName+"获取口红的锁");            }        }    }

线程A拿到了口红锁，然后释放了口红锁，想拿镜子锁

运行结果

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