This is because B is not in the classpath of the system class loader or its parent or ancestor class loaders.

这是因为 B 不在系统类装入器或者它的双亲或祖先类装入器的类路径中。

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A subclass that implements a subtype does not override the behavior of its ancestor class; it only extends the services provided by that class.

具备子类型的子类不能覆盖其祖先类的行为，而只能扩展其祖先类提供的服务。

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As with the field calls, the first two variants return information for public methods that can be accessed through the class — even those inherited from an ancestor class.

与字段调用一样，前两个变量返回可以通过类接入的公共方法的信息——即使它们来自于祖先类。

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