一道面试题：用synchronized实现lock锁

/**
 * 用synchronized实现lock锁
 */
public class MyLock {
    private final static long NONE = -1;
    private long owner = NONE;

    public synchronized void lock(){
        long currentThreadId = Thread.currentThread().getId();
        if(owner==currentThreadId){
            System.out.println("Thread is has lock");
        }
        while(owner!=NONE){
            try{
                System.out.println(String.format("%s want to lock",currentThreadId));
                wait();
            }catch (Exception e){
                e.printStackTrace();
            }
        }
        owner=currentThreadId;
        System.out.println(String.format("%s get lock",currentThreadId));
    }

    public synchronized void unlock(){
        long currentThreadId = Thread.currentThread().getId();
        if(owner!=currentThreadId){
            System.out.println("Only lock owner can unlock the lock");
        }
        System.out.println(String.format("thread %s is unlocking", owner));
        owner=NONE;
        notify();
    }
    public static void main(String[] args) {
        MyLock lock = new MyLock();
        Thread thread1 = new Thread(new Runnable() {
            @Override
            public void run() {
                lock.lock();
                System.out.println(String.format("thread %s is running...", Thread.currentThread().getId()));
                try{
                    Thread.sleep(3000);
                }catch (Exception e){
                    e.printStackTrace();
                }
                lock.unlock();
            }
        });
        Thread thread2 = new Thread(new Thread(new Runnable() {
            @Override
            public void run() {
                lock.lock();
                System.out.println(String.format("thread %s is running...", Thread.currentThread().getId()));
                try{
                    Thread.sleep(3000);
                }catch (Exception e){
                    e.printStackTrace();
                }
                lock.unlock();
            }
        }));
        thread1.start();
        thread2.start();
    }
}

运行结果如下

11 get lock
13 want to lock
thread 11 is running...
thread 11 is unlocking
13 get lock
thread 13 is running...
thread 13 is unlocking