[BlackFly]

The final keyword is one of those places where Java shows its age to me. I agree with the overall point that inheritance is flawed, but I cannot bring myself to conclude that the use of final is the answer to the problem.

Simple example, String is final in Java. It is also immutable, and that is (mostly) irrelevant. Lots of string fields on inbound requests have validations, a simple one would be a field that contains a fixed length string. So obviously you validate that at the ingress before passing it down. Now, the question arises, should the core library be defensive and re-validate the string? Why not simply capture the subtype, TenCharacterString and parameterize methods with that?

Modern languages get this right. Subtyping is not inheritance. Inheritance is not subtyping. I should be able to subtype at zero cost, I don't need inheritance to do that, [and encapsulation is definitely not subtyping].

But Java doesn't have that. You mark something as final and you lose the ability to subtype just to eliminate the possibility of inheritance. On the other hand, to be fair to the argument against final, the real answer to my complaint is a proper type aliasing support.

[rzzzt]

The "extends" keyword gives it away that inheritance in Java was not positioned to support the restrictive cases you have in mind (Square : Rectangle, NegativeNumber : Number, TenCharacterString : String).

What issues do you see with wrapping? TenCharacterString eg. could use char[] as its backing store and implement CharSequence if you want to get it to speak a common language with String.