.travis.yml: add oraclejdk9

[PascalSchumacher]

No description provided.

[kinow]

Looks like it's not quite ready yet. Had a look at the ticket mentioned below, and followed links to other tickets, and looks like it's still WIP. So let's wait until Java 9 is released to merge it (WAS: +1 lgtm!)

[britter]

Travis build failed. Any idea why? Java 8 has an heap space error, while the Java 9 build reports an unrecognized VM option.

[kinow]

Ooh, looked at the wrong green icon. JDK 7 complained about JAVA_HOME location... weird. Related issue in travis-ci repo travis-ci/travis-ci#5520

[PascalSchumacher]

Another problem is that the maven version used by travis does not work with jdk 9 as far as I know.

[ameyjadiye]

As per Travis-ci documentation doesnt seems they support oraclejdk9

https://docs.travis-ci.com/user/languages/java/

The Travis CI environment provides Oracle JDK 7 (default), Oracle JDK 8, OpenJDK 6, OpenJDK 7, Gradle 2.0, Maven 3.2 and Ant 1.8, and has sensible defaults for projects that use Gradle, Maven or Ant.

Thats why I added Docker Image for ibmjdk8 to Commons text apache/commons-text#45

[PascalSchumacher]

It is not officially supported, but it is possible.

For example https://github.com/jacoco/jacoco and https://github.com/apache/logging-log4j2 use jdk 9 on travis.

[ameyjadiye]

Hmm, how about using docker service for this ? , I have raised same for ibmjdk8 #271

[PascalSchumacher]

The build works using java 9 locally. I guess its only a few months at most until jdk 9 will be officially supported on travis, so I won't invest any more time into this for now.