如何从基类方法中重写方法调用？

Question

根据docs on inheritance：

Derived classes may override methods of their base classes. Because methods have no special privileges when calling other methods of the same object, a method of a base class that calls another method defined in the same base class may end up calling a method of a derived class that overrides it.

怎么会这样？有人能用一个简单的例子来说明这个概念吗？