Kotlin ClassĪ class is a blue print defined which groups functions and properties. We will also look at kotlin constructors, access modifiers and abstract class. Code C now uses Class B and has no access to the protected API of Class A via Class B, whereas, if the protected visibility had been public instead, Code C could have used the protected API of Class B, despite Library B’s intentions.In this tutorial, we’ll be discussing the Object Oriented Programming concepts of Kotlin.The protected API of Class A in Library A is now an implementation detail of Class B in Library B.Class B is still public API for consumption by Code C.Class B is final/not designed for extension.

Class B uses the protected API of Class A.

Library B has a Class B that is a subclass of Class A.

Library A has a Class A in its API designed for extension with an API with protected visibility.

The only hypothetical case for protected that I know of is as follows: If protected is used to expose functionality to subclasses of a public class in an API, it is redundant with the public visibility. Similar to private, if protected is used for internal code, it is redundant with “internal” visibility. The protected modifier for subclasses is nearly useless as well. The detriment of the noise of the private modifier outweighs the benefit of having implementation details within implementation details via the private modifier. Having code encapsulated in a class offers little benefit over having code encapsulated in a package/build module/etc. Everything should default to an “internal” visibility, where “internal” code is implementation details (of a package, build module, or whatever the code is packaged in that ships functionality via a public API). Code is either API or implementation details. Public is the only worthwhile visibility qualifier. Public is the Only Worthwhile Visibility Modifier

Internal kotlin modifier