覆盖方法时,为什么我可以增加访问权限但不能减少访问权限? [英] When overriding a method, why can I increase access but not decrease it?
问题描述
为什么 Java 指定覆盖方法的访问说明符可以允许比覆盖方法更多但不能更少的访问?例如,超类中的受保护实例方法可以在子类中设为公有,但不能设为私有.
Why does Java specify that the access specifier for an overriding method can allow more, but not less, access than the overridden method? For example, a protected instance method in the superclass can be made public, but not private, in the subclass.
推荐答案
这是 OOP 中的一个基本原则:子类是父类的成熟实例,因此必须至少呈现相同 接口作为父类.使受保护/公共事物不那么明显会违反这个想法;您可以使子类无法用作父类的实例.
It's a fundamental principle in OOP: the child class is a fully-fledged instance of the parent class, and must therefore present at least the same interface as the parent class. Making protected/public things less visible would violate this idea; you could make child classes unusable as instances of the parent class.
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