Migrate to Java 11

I read a bit about current Java development, so I open this issue for discussion:

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Java 11 (released in Sept. 2018) is the next long-term-support version after Java 8. So I guess at some point we should consider migrating. Normally, this should be easy - however, we have seen issues (compile errors) with Java versions > 8. Not sure how serious they are, i.e. how easy to fix.

There has been a lot of development after Java 8 (apparently the module system, introduced in Java 9, had a larger impact, https://en.wikipedia.org/wiki/Java_Platform_Module_System).

from source: https://medium.com/criciumadev/its-time-migrating-to-java-11-5eb3868354f9 :

• The end of live of Java 8 is January 2019 (this month) - after this there are no public updates anymore.
• For advantages listed at "Why upgrade from JDK 8 to JDK 11?" (security and increased speed and better garbage collection)
• tutorial to migrate from Java 8 -> 11 with Maven

There are many sources on the internet about the migrating step:

• https://codete.com/blog/java-8-java-11-quick-guide/
• https://blog.codefx.org/java/java-11-migration-guide/
• https://www.avision-it.de/2018/09/25/goodbye-java-8-hello-java-11/
• https://winterbe.com/posts/2018/08/29/migrate-maven-projects-to-java-11-jigsaw/