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From: Mostowski Collapse <janburse@fastmail.fm>
Newsgroups: comp.lang.java.programmer
Subject: Re: JSR 401
Date: Thu, 1 Apr 2021 16:44:10 +0200
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LoL

Eric Sosman schrieb:
> 
> Has anyone else studied the working drafts of the forthcoming JSR 401?
> It's an attempt to unify "primitives" and "objects" in a future Java,
> making it possible to have a List<int> instead of List<Integer>, or a
> Map<short,double> instead of Map<Short,Double>, and so on. It would
> also allow arrays of generic types, like JList<String>[], relieving an
> irritation that's nagged us since the dawn of generics.
> 
> But there's a drawback: Although arrays of objects (even of generic
> types) will work, arrays of primitives would no longer be possible!
> That is, you could no longer create or use an int[], but would need
> to use something like an ArrayList<int> instead. I'm not intimate
> with the inner workings of the JVM and I fail to understand some of
> the problems the working papers describe, but it has something to do
> with the fact that an array knows the type of its elements and a
> primitive doesn't actually have a "type" in the sense of belonging to
> a class hierarchy.
> 
> Unless I've misunderstood (I *hope* I've misunderstood!), this is both
> surprising and dismaying. "Surprising" because the principal author of
> this section of the JSR is Pola Flori, who's worked on earlier JSR's
> that were scrupulous about maintaining backwards compatibility. Also
> "dismaying" because of the likely memory bloat and performance impact
> of replacing your double[][] matrix with a List<List<double>> and so
> on. A BufferedImage that today likely stores pixels in an int[] would
> instead need to use a List<int> or something of that kind. I can't
> imagine that this would be a Good Thing ...
> 
> But as I say, I may have misunderstood. I hope someone more familiar
> with JVM internals and more adept at decoding JSL-style language will
> study the proposed JSR and tell me I'm completely wrong. It's a work
> in progress rather than an official JSR, so you'll find it hosted at
> 
> https://enterrasolutions.com/wp-content/uploads/2019/04/000156-0021-000078_2.png 
> 
>