Editing Fragile base class (section)

==Solutions==
* [[Objective-C]] has [[Objective-C#Categories|categories]] as well as [[Objective-C#Non-fragile instance variables|non-fragile instance variables]].
* [[Component Pascal]] deprecates [[Superclass (computer science)|superclass calls]].
* [[Java (programming language)|Java]], [[C++]] (Since C++11) and [[D (programming language)|D]] allow inheritance or overriding a class method to be prohibited by labeling a declaration of a class or method, respectively, with the keyword "<code>final</code>". In the book ''Effective Java'', author [[Joshua Bloch]] writes (in item 17) that programmers should "Design and document for inheritance or else prohibit it".
* [[C Sharp (programming language)|C#]] and [[VB.NET]] like Java have "<code>sealed</code>" and "<code>Not Inheritable</code>" class declaration keywords to prohibit inheritance, and require a subclass to use keyword "<code>override</code>" on overriding methods,<ref>{{Cite web | url=https://msdn.microsoft.com/en-us/library/ebca9ah3.aspx | title=Override modifier - C# Reference }}</ref> the same solution later adopted by Scala.
* [[Scala (programming language)|Scala]] require a subclass to use keyword "<code>override</code>" explicitly in order to override a parent class method. In the book "Programming in Scala, 2nd Edition", the author writes that (with modifications here) If there was no method f(), the client’s original implementation of method f() could not have had an override modifier. Once you add the f() method to the second version of your library class, a recompile of the client code would give an compile error instead of wrong behavior.
* In [[Kotlin (programming language)|Kotlin]] classes and methods are final by default. To enable the class inheritance, the class should be marked with the <code>open</code> modifier. Likewise, a method should be marked as <code>open</code> to allow overriding of the method.
* [[Julia (programming language)|Julia]] allows only subtyping of abstract types and uses composition as an alternative to [[Inheritance (object-oriented programming)|inheritance]]. It however has [[multiple dispatch]].