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

java inheritance access-modifiers
yesilupper picture yesilupper · Jul 27, 2011 · Viewed 49.5k times · Source

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

Patrick87 picture Patrick87 · Jul 27, 2011

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.

Related questions

Implements vs extends: When to use? What's the difference?

Please explain in an easy to understand language or a link to some article.

Read More
How to determine an object's class?

If class B and class C extend class A and I have an object of type B or C, how can I determine of which type it is an instance?

Read More
How should I have explained the difference between an Interface and an Abstract class?

In one of my interviews, I have been asked to explain the difference between an Interface and an Abstract class. Here's my response: Methods of a Java interface are implicitly abstract and cannot have implementations. A Java abstract class can …

Read More