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

Florian Weimer fweimer at bfk.de
Thu Jun 18 02:34:49 PDT 2009

On Thu, 2009-06-18 at 11:06 +0200, Florian Weimer wrote:

Obviously, this heavily constrains the solution space. In the end, Java 5 bytecode could not run on pre-Java 5 VMs, so this requirement was somewhat pointless, wasn't it? Neal answered this question in a blog entry a few years ago: http://gafter.blogspot.com/2004/09/puzzling-through-erasure-answer.html

Java's equivalent of DLL hell described in that post is very real, but it happens all the time because most library authors lack a firm commitment to backwards compatibility, with or without generics.

But my point was precisely that avoiding versioning hell doesn't work with Java 5 generics because as soon as you put them in your code, you have to compile with a generics-enabled javac, and there is no Sun-supported way to make its output work with javac from 1.4. As a result, the migration to generics still hasn't happened widely. Most of the libraries we use still don't use generics, not even for collections classes they use internally.

I don't know for certain what this means for the future. It seems to suggest that aiming for the level of binary compatibility Neal described is just unrealistic. There's no reason to assume that the next iteration would be any different.

-- Florian Weimer <fweimer at bfk.de> BFK edv-consulting GmbH http://www.bfk.de/ Kriegsstraße 100 tel: +49-721-96201-1 D-76133 Karlsruhe fax: +49-721-96201-99

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