Become an early Java 9 expert: AJUG + vJUG + JUGs Worldwide Hackday Feedback on JDK 9 EA

Mani Sarkar sadhak001 at
Fri Sep 22 14:21:04 UTC 2017

Thanks Alex for the response, and clarifying the question further with your

There a few issues reported as well, would you want to comment on them,
should I put them on a separate thread for further discussions?


On Wed, 20 Sep 2017 at 02:54 Alex Buckley <alex.buckley at> wrote:

> Hi Mani,
> On 9/19/2017 2:55 PM, Mani Sarkar wrote:
> > Last month (19th August 2017) AJUG and a number of JUGs worldwide with
> the
> > help and support from vJUG, re-ran the  "Become an early Java 9 expert"
> > hackday.
> Thank you AJUG and vJUG!
> > You can find the feedback gathered in
> > we have been trailing JDK 9 EA b181 (RC1).
> A lot of feedback seems to boil down to "JDK command line tools are not
> so easy to use; I want my IDE!". I don't mean to make light of people's
> usability issues, but the module-related paths and flags in JDK 9 tools
> tend to operate along similar lines as the paths and flags in JDK 8
> tools -- it's just that a lot of people haven't set ANY paths and flags
> for a long time.
> I see there were some more open-ended questions and this one in
> particular caught my attention:
> -----
> Do I need to convert a legacy Java program to use named modules in order
> to take advantage of the smaller images that jlink can create?
> Mani: You will have to convert your applications to use Java 9’s modules
> system in order to take advantage of JLink fully, although please play
> around with older legacy apps to see what JLink produces (most likely
> the whole JDK and not modularised pieces).
> Simon: create an empty module with and handcraft the
> dependencies using requires and have jlink compile it. This is
> experimental, would need to be tested to see how it works.
> -----
> The direct answer to the question is "No, you do not need to convert a
> legacy Java program to use named modules in order to take advantage of
> the smaller images that jlink can create."
> The Java runtime that's present in even the smallest image (just
> java.base) still lets you to put your pre-existing JAR files on the
> classpath and run them with java -cp. You do not need to turn your JAR
> files into named modules. Even as traditional JAR files, they have
> access to all the APIs that you would expect from such an image.
> (Obviously if your JAR files try to use Swing on an image built from
> just java.base, that won't work.) The reduced footprint and security
> surface of the smaller image is plainly an advantage from jlink.
> Alex
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