一个简单的死锁

public class DeadLock3 implements Runnable {
    
    private static Object obj1 = new Object();
    private static Object obj2 = new Object();

    @Override
    public void run() {
        System.out.println("Current Thread: " + Thread.currentThread().getName());
        for (int i = 1; i < 3; i++) {
            System.out.println("i: " + i);
            if (i % 2 != 0) {
                //odd
                System.out.println("Lock object1 first then lock object2");
                synchronized (obj1) {
                    try {
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    synchronized (obj2) {}
                }
            } else {
                //even
                System.out.println("Lock object2 first then lock object1");
                synchronized (obj2) {
                    try {
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    synchronized (obj1) {}
                }
            }
        }
    }

    public static void main(String[] args) {
        new Thread(new DeadLock3()).start();
        new Thread(new DeadLock3()).start();
    }
}

从运行结果可以看出，Thread-0和Thread-1都进入了run方法，Thread-0是先锁住object1再锁住object2, 而Thread-1则相反，当Thread-0成功锁住object1再试图去锁定object2的时候，发现object2已经被Thread-1锁住了，于是Thread-0只好等在那里，等待Thread-1释放object2的锁； 这个时候，Thread-1成功锁住了object2再试图去锁住object1的时候发现object1已经被锁住了，于是只好等在那里，等待Thread-0释放object1的锁，于是造成了相互等待的死锁现象。

利用java内置的工具jps可以查看当前JVM正在运行的Java线程

利用java内置的工具jstack可以查看某线程的情况，例如是否死锁