JEP 238: Multi-Version JAR Files

dalibor topic dalibor.topic at
Fri Feb 13 15:38:38 UTC 2015

On 13.02.2015 15:41, Ivan St. Ivanov wrote:
> Hi Richard,
> I'm not completely sure. about that. What I know is that JEP 220 (Modular
> runtime images) says that a new format should be introduced that will
> replace the jar. I guess it is the jmod thing. But I have to double check
> it.

JEP 220 talks about enhancements necessary to modularize the runtime 
image of the JDK/JRE itself. While its goals include a new more 
efficient format for class and resource data previously stored in the 
JAR files in lib/, to quote from the relevant section: "The format of 
these files will not be specified and is subject to change without 

dalibor topic

> Regards,
> Ivan
> On Fri, Feb 13, 2015 at 4:07 PM, Richard Warburton <
> richard.warburton at> wrote:
>> Hi Ivan,
>> I saw this in the morning and didn't dare to comment in the core libs
>>> group, but I guess that the adoption mailing list is good enough for my
>>> question.
>>> So, in Java 9 we are hopefully going to have Jigsaw. One of its features
>>> is
>>> retiring the jar format. Yes, the jar will still be supported for the sake
>>> of backward compatibility, but I don't get why they plan to enhance it
>>> further with this feature. The reason "we are going to downport it to Java
>>> 8u60" does not hold in my books.
>>> Am I the only one that feels that this is spending time and resources on
>>> feature that OpenJDK plans to replace (the jar format)?
>> I think either you've got the wrong end of the stick here, or maybe I
>> have! My understanding is that the jar format isn't going away. It would
>> still be the format used to distribute something like a library. Jigsaw may
>> offer other features on top of what a jar offers, but jars would still be
>> around.
>> regards,
>>    Richard Warburton
>>    @RichardWarburto <>

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