Github user afs commented on the issue:
https://github.com/apache/jena/pull/474
@lewismc
> @afs how about we propose the change to
>
> ```
> <additionalOptions>-html4</additionalOptions>
> ```
> This would produce JDK WARNING's under several environment's however
would at least enable successful build under this environments.
The problem is not html4/html5 (we can clean up the javadoc) but compatible
with java8 javadoc tool. Java8 build causes:
Exit code: 1 - javadoc: error - invalid flag: -html4
I'd prefer that the build uses java8 for java8 libraries because
cross-compiling does not catch changes in the runtime libraries.
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