为什么不能降低 Java 子类中方法的可见性? [英] Why can't you reduce the visibility of a method in a Java subclass?

问题描述

为什么当您在子类中重写方法时降低了方法的可见性时编译器会给出错误消息?

Why does the compiler give an error message when you reduce the visibility of a method while overriding it in the subclass?

推荐答案

因为子类的每个实例仍然需要是基类的有效实例(参见 Liskov 替换原则).

Because every instance of the subclass still needs to be a valid instance of the base class (see Liskov substitution principle).

如果子类突然失去了基类的一个属性(例如公共方法)，那么它将不再是基类的有效替代品.

If the subclass suddenly has lost one property of the base class (namely a public method for example) then it would no longer be a valid substitute for the base class.

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