下面的代码使用lock对象以避免死锁情况。
在函数impendingbow中，两个对象如何同时获得锁：当前对象和朋友bower？

myLock = lock.tryLock();
yourLock = bower.lock.tryLock();

是因为它是两个不同的物体吗？如果是的话，这是否意味着对少数对象使用一个锁就足够了？
有人能解释一下在这个实现中我们是如何避免死锁的吗？
以下是完整代码：

public class Safelock {
    static class Friend {
       private final String name;
       private final Lock lock = new ReentrantLock();

    public Friend(String name) {
        this.name = name;
    }

    public String getName() {
        return this.name;
    }

    public boolean impendingBow(Friend bower) {
        Boolean myLock = false;
        Boolean yourLock = false;
        try {
            myLock = lock.tryLock();
            yourLock = bower.lock.tryLock();
        } finally {
            if (! (myLock && yourLock)) {
                if (myLock) {
                    lock.unlock();
                }
                if (yourLock) {
                    bower.lock.unlock();
                }
            }
        }
        return myLock && yourLock;
    }

    public void bow(Friend bower) {
        if (impendingBow(bower)) {
            try {
                System.out.format("%s: %s has"
                    + " bowed to me!%n", 
                    this.name, bower.getName());
                bower.bowBack(this);
            } finally {
                lock.unlock();
                bower.lock.unlock();
            }
        } else {
            System.out.format("%s: %s started"
                + " to bow to me, but saw that"
                + " I was already bowing to"
                + " him.%n",
                this.name, bower.getName());
        }
    }

    public void bowBack(Friend bower) {
        System.out.format("%s: %s has" +
            " bowed back to me!%n",
            this.name, bower.getName());
    }
}

static class BowLoop implements Runnable {
    private Friend bower;
    private Friend bowee;

    public BowLoop(Friend bower, Friend bowee) {
        this.bower = bower;
        this.bowee = bowee;
    }

    public void run() {
        Random random = new Random();
        for (;;) {
            try {
                Thread.sleep(random.nextInt(10));
            } catch (InterruptedException e) {}
            bowee.bow(bower);
        }
    }
}