Java中的线程:如何锁定对象？

public class SynchronizedExample {
    public static void main(String[] args) {
        MyThread myThread = new MyThread();
        Thread thread1 = new Thread(myThread);
        Thread thread2 = new Thread(myThread);

        thread1.start();
        thread2.start();
    }
}

class MyThread implements Runnable {
    private Object lock = new Object();

    @Override
    public void run() {
        synchronized (lock) {
            System.out.println(Thread.currentThread().getName() + "获得了锁");
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "释放了锁");
        }
    }
}