Suggestions for Java Generics Semantics in Java Version 7.0 _ Resurrected (original) (raw)

David Herron david at davidherron.com
Wed Jun 17 15:08:35 PDT 2009

Hey Alex,

This is a very well put argument about the situation. I certainly don't have the basis for commenting on the technological underpinnings of anything you have said.

The thing I want to point to is that item #3 follows a "Sun provides the technology, you guys consume the technology" attitude. In the spirit of an open source community process perhaps #3 could be reworded to say that Sun's priorities are clear from where Sun is placing it's R&D dollars, and if a group were to form in the community to implement reification ...etc...

In other words, notwithstanding the prestige of the names you listed in point #2, it may be possible with enough work for some set of people to implement reification. I would hope that if the community were to do it, that it could be accepted into the OpenJDK. Maybe some people in the community have a different prioritization of needs than Sun has?

On Wed, Jun 17, 2009 at 12:21 PM, Alex Buckley <Alex.Buckley at sun.com> wrote:

1) Sun's bug database categorizes an entry as either a defect or a request for enhancement. Bug 5098163 is, rightly, a request for enhancement. It is not a defect that type erasure exists. I will say that again. Type erasure is not a bug. It is a feature.

2) The reason it is a feature is that many experts - including but not limited to Philip Wadler, Martin Odersky, Gilad Bracha, Joshua Bloch, and Neal Gafter - worked for many years on crafting a generic type system that allowed people to migrate their non-generic clients and libraries smoothly. Reified generics would have made that migration more complex. If you don't know why, find out. 3) While there were good reasons for avoiding it, there is no doubt that reified generics make the Java language itself more regular. No doubt at all. The question we face TODAY is, are reified generics MORE valuable than other features that Sun can add to the Java platform. Evidently not, since Sun is working on other features. Again, I don't want to prolong this conversation, but perhaps you could say which JDK7 feature(s) you would drop to make room for reified generics? You can choose from the list at http://openjdk.java.net/projects/jdk7/features/ Alex

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