dockerfile/java missing from docker hub

[chigozienri]

dockerfile/java has been removed from docker hub, so the Dockerfiles that rely on it in their FROM statements are broken. See dockerfile/java#32
openjdk on dockerhub can be used instead https://hub.docker.com/_/openjdk/

[ctrueden]

Fixed by your #8 PR, right?

[chigozienri]

Yes, should be fixed by my PR