JEP 238: Multi-Version JAR Files

Stephen Colebourne scolebourne at
Thu Feb 12 22:59:24 UTC 2015

Interesting direction.

Reading carefully, the goal is actually very limited in scope, by
preventing any public API changes. It doesn't help adoption of JSR-310
for example, but will be useful for Unsafe, which is clearly a
motivating factor.

I would expect IDEs to have some considerable work to do.

My biggest concern will be ensuring tools like Reflections (or other
classpath scanning tools) carry on working. Really, classpath scanning
should no longer be necessary with a module system, but since we've
heard nothing to indicate that issue is being tackled, those tools
will continue to be vital (such as to find all classes implementing an
annotation, or all implementations of an interface)


On 12 February 2015 at 20:52, Paul Sandoz <paul.sandoz at> wrote:
> Hi
> In connection with the JEP there is also a design document to help the discussion:
> We are especially interesting in hearing feedback from library developers, tool/IDE developers, and anyone doing funky stuff with class loading and JAR files.
> Paul.
> On Feb 12, 2015, at 9:41 PM, mark.reinhold at wrote:
>> New JEP Candidate:
>> - Mark

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