死锁-嵌套容易发生死锁

朱雀 2022-06-10 00:45 259阅读 0赞

直接看例子：

public class DealThread implements Runnable{
        public String username;
        public Object lock1=new Object();
        public Object lock2=new Object();
        public void setFlag(String username){
            this.username=username;
        }
        @Override
        public void run() {
            if(username.equals("a")){
                synchronized (lock1){
                    try {
                        System.out.println("username = "+username);
                        Thread.sleep(3000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    synchronized (lock2){
                        System.out.println("按lock1->lock2代码顺序执行了");
                    }
                }
            }
            if(username.equals("b")){
                synchronized (lock2){
                    try {
                        System.out.println("username = "+username);
                        Thread.sleep(3000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    synchronized (lock1){
                        System.out.println("按 lock2->lock1代码顺序执行了");
                    }
                }
            }
        }
    }

public class Run {
        public static void main(String[] args){
            try {
                DealThread t1=new DealThread();
                t1.setFlag("a");
                Thread thread1=new Thread(t1);
                thread1.start();
                Thread.sleep(100);
                t1.setFlag("b");
                Thread thread2=new Thread(t1);
                thread2.start();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

你在的等我，我在等你，就永远等了= =（要行动起来啊）