JDK 12: RC feedback

Andrew Guibert aguibert at us.ibm.com
Tue Feb 19 17:03:54 UTC 2019

Hi all, 
I am kicking the tires on the JDK 12 release candidate build, and I noticed two major pain points:
1) javac source/target 6 option is no longer supported
Looking through the release notes [1] I see no mention of this change. Is it part of some more generic policy that javac will only go back N-5 versions?  Dropping source/target 6 specifically is not my primary concern, rather a more general concern of the cadence of the min compliance dropoff (JDK 9 dropped source/target 5 iirc). If this is the case I worry that by JDK 14 (about a year from now), we will no longer be able to compile down to source/target 8, which will still be a very popular runtime version in 1 years time (and still a supported version).
2) The java.class.version has increased (again)
Looking through the release notes, I don't see any major bytecode improvements that signal to me that the class file major version needed to be incremented. Is this being incremented as part of some automatic policy? Major class version updates are extremely disruptive to the java ecosystem, mainly because so many things depend on ASM (or other bytecode libs) somewhere in the stack.
Given the 6 month release cadence of Java, this is going to cause a lot of churn in the Java community if we have to wait for ASM to cut a new release before the rest of the community can upgrade, severely cutting into the 6 month lifespan of the non-LTS JDKs.
I understand that the JDK reserves the right to increase the class major version on each release, but I ask that you do so sparingly (perhaps every other release at most?).
[1] https://jdk.java.net/12/release-notes
Andrew Guibert
IBM - OpenLiberty / WebSphere Liberty development

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