Open-closed principle and Java “final” modifier

Question

The open-closed principle states that \"Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification\".

However, J

Answer 1

The two statements

Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification.

and

Design and document for inheritance, or else prohibit it.

are not in direct contradiction with one another. You can follow the open-closed principle as long as you design and document for it (as per Bloch's advice).

I don't think that Bloch states that you should prefer to prohibit inheritance by using the final modifier, just that you should explicitly choose to allow or disallow inheritance in each class you create. His advice is that you should think about it and decide for yourself, instead of just accepting the default behavior of the compiler.