java - When overriding a method, why can I increase access but not decrease it?

Question

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.

Answer 1

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.