Regardless of how they might have used LLMs, I tend to have an issue with this kind of complaint, given the C++ example code on the Design Patterns: Elements of Reusable Object-Oriented Software book, released in 1994, 2 years before Java was made public.

Or the examples from "Using the Booch Method: A Rational Approach", "Designing Object Oriented C++ Applications Using The Booch Method", or "Using the Booch Method: A Rational Approach".

Additional there are enough framework examples starting with Turbo Vision in 1990, MacAPP in 1989, OWL in 1991, MFC in 1992,....

Somehow a C++ style that was prevalent in the industry between 1990 and 1996, that I bet plenty of devs still have to maintain in 2026, has become "Java in C++".

But the pattern applies regardless of the validation logic.

It's just a toy example not a production ready birthday validation library.