It seems Java has had the power to declare classes not-derivable for ages, and now C++ has it too. However, in the light of the Open/Close principle in SOLID, why would that be useful? To me, the final keyword sounds just like friend – it is legal, but if you are using it, most probably the design is wrong. Please provide some examples where a non-derivable class would be a part of a great architecture or design pattern.
Java – Why would the ‘final’ keyword ever be useful
cfinaljavasolid
Best Answer
finalexpresses intent. It tells the user of a class, method or variable "This element is not supposed to change, and if you want to change it, you haven't understood the existing design."This is important because program architecture would be really, really hard if you had to anticipate that every class and every method you ever write might be changed to do something completely different by a subclass. It is much better to decide up-front which elements are supposed to be changeable and which aren't, and to enforce the unchangeablility via
final.You could also do this via comments and architecture documents, but it is always better to let the compiler enforce things that it can than to hope that future users will read and obey the documentation.