写一个死锁

死锁

public class Test03 {

    Object lock1 = new Object();
    Object lock2 = new Object();

    public void method1() {
        synchronized (lock1) {
            synchronized (lock2) {
                System.out.println("method 1 .... ");
            }
        }
    }

    public void method2() {
        synchronized (lock2) {
            synchronized (lock1) {
                System.out.println("method 2 .... ");
            }
        }
    }
    
    public static void main(String[] args) {
        Test03 test03 = new Test03();
        new Thread(() -> {
            while (true) {
                test03.method1();
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }).start();

        new Thread(() -> {
           while (true) {
               test03.method2();
               try {
                   Thread.sleep(100);
               } catch (InterruptedException e) {
                   e.printStackTrace();
               }
           }
        }).start();
    }
}

执行结果：

> Task :Test03.main()
method 1 .... 
method 2 .... 

发生死锁，打印也被阻塞

检测死锁：

1. jvisualvm 工具 ，
2. 命令行工具
   jps 找到我们运行的程序 pid
   jstck pid