可重入锁 – 实践中的Java并发

class Widget {
public synchronized void doSomething() {
    System.out.println(toString() + ": calling superclass doSomething");
}


}

class LoggingWidget extends Widget {
public synchronized void doSomething() {
    System.out.println(toString() + ": calling subclass doSomething");
    super.doSomething();
}
}

这本书在上面的代码中解释了……
“因为Widget和LoggingWidget中的doSomething方法都是同步的,所以每个方法都会在继续之前尝试获取Widget上的锁定.”

我运行上面的代码来观察内在锁.上面的引用似乎暗示一个线程获取Widget对象的内部锁,但我观察到的是该线程获取了LoggingWidget上的锁.我不确定如何验证采集计数,所以无法观察到.

该书是否可以互换地使用名称LoggingWidget / Widget,还是应该特意观察Widget对象的锁定？

编辑：完整摘录

Reentrancy facilitates encapsulation of locking behavior,and thus
simplifies the development of object-oriented concurrent code. Without
reentrant locks,the very natural-looking code in Listing 2.7,in
which a subclass overrides a synchronized method and then calls the
superclass method,would deadlock. Because the doSomething methods in
Widget and LoggingWidget are both synchronized,each tries to acquire
the lock on the Widget before proceeding. But if intrinsic locks were
not reentrant,the call to super.doSomething would never be able to
acquire the lock because it would be considered already held,and the
thread would permanently stall waiting for a lock it can never
acquire. Reentrancy saves us from deadlock in situations like this.