Feedback and comments on ARM proposal (original) (raw)

Jeremy Manson jeremy.manson at gmail.com
Fri Mar 20 13:02:35 PDT 2009

On Thu, Mar 19, 2009 at 5:55 PM, Joshua Bloch <jjb at google.com> wrote:

especially considering your disagreement with Howard and

Jeremy about declaration scope rather than a new block-structured statement form,

Not really a disagreement. In the end, we both came to the conclusion that block-structured was probably the right thing for Java today.

I really don't want to interject myself here, but in the interests of clarity and not being misrepresented by anyone, I will say what I actually think about the proposal.

I like it.

In an ideal world, in a language that we could start from scratch, I would like declaration scoping. Java is not such a language. In Java, nothing meaningful happens when variables go out of scope, other than that they are not lexically available. It doesn't even mean that objects pointed to are now unreachable -- a compiler can decide to make objects unreachable before the only variables pointing to them go out of scope! Having semantics for nested scopes is a C++-ism, not a Java-ism.

I think it would be nice to have support for opening and closing resources in a way that does not require you to declare a variable (just as the standard for loop doesn't require you to declare a variable in the initializer). I don't think that that is actually all that important by comparison with what the proposal provides, and I believe it can be retrofitted later (potentially in a later Java revision) if we decide it is necessary. I think the biggest reason to include it now is probably that everyone will be asking why we didn't include it.

Jeremy

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