Evolving the wrapper classes
brian.goetz at oracle.com
Wed Jun 17 22:45:06 UTC 2020
> Hmm, just maybe this will be less confusing than I was fearing. I'm
> seeing now that "Integer is the real class, int is alias for
> Integer.val" is a whole lot cleaner than "int becomes a val-default
> class and Integer is demoted to alias for int.ref", which for some
> reason was the way I was thinking of it.
I'm sure that, sometime during the evolution, I probably said it the way
you remember. Then Dan came along and cleaned it up :)
> Java language/compiler changes (when --enable-preview is set):
> - The class file reader knows how to find the special
> Integer.class and Integer$val.class.
> - The type 'Integer.val' is equivalent to 'int'. Primitive types
> are inline types—they have members, support method invocation, etc.
> This at least /suggests /that `42L.hashCode()` would begin to work
> just as `"foo".hashCode()` does?
We certainly have that option. We could decide to not take it, on the
theory that it scares the neighbors, but it does seem sensible to just
say "0L is a long-valued expression" and "long implements XYZ
interfaces", and let the neighbors be scared for a few minutes.
> Users /can/ write `Integer.val` in their code, but would there ever be
> a good reason to? I assume we would always prefer `int`. And this
> actually makes me wonder if it's worth considering also allowing
> `int.ref` to be an alias for `Integer` because it would allow users to
> drop the word `Integer` from their code more completely, and therefore
> `int` would look more and more like it was just an inline type like
> any other. It reminds you that the old boxing/unboxing isn't in play
> anymore. And `int.ref` is more self-evidently something you can't
> synchronize on, etc. But, what would remain weird is that you don't
> /actually /find a val-default class called `int` sitting in an
> `int.java` file.
Right, there's a set of pros and cons here, none of which are
technical. Being able to say `int.ref` makes it more clear that `int`
and `Point` are the same thing, but on the other hand, it raises issues
of "there are two ways to say the same thing, so let's have an endless
debate about it."
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