EG meeting, 2021-11-17

[Kevin Bourrillion]

On Wed, Nov 17, 2021 at 7:05 PM Dan Heidinga <heidinga at redhat.com> wrote:

Let me turn the question around: What do we gain by allowing
> subclassing of B2 classes?
>

I'm not claiming it's much. I'm just coming into this from a different
direction.

In my experience most immutable (or stateless) classes have no real
interest in exposing identity, but just get defaulted into it. Any
dependency on the distinction between one instance and another that
equals() it would be a probable bug.

When B2 exists I see myself advocating that a developer's first instinct
should be to make new classes in B2 except when they *need* something from
B1 like mutability (and perhaps subclassability belongs in this list too!).
As far as I can tell, this makes sense whether there are even *any *performance
benefits at all, and the performance benefits just make it a lot more
*motivating* to do what is already probably technically best anyway.

Now, if subclassability legitimately belongs in that list of
B1-forcing-factors, that'll be fine, I just hadn't fully thought it through
and was implicitly treating it like an open question, which probably made
my initial question in this subthread confusing.



-- 
Kevin Bourrillion | Java Librarian | Google, Inc. | kevinb at google.com