switch to Java 11

[kohlhase]

it is the new lts version.

[tkw1536]

I have updated:

• the Travis Tests to test on both Java 8 and Java 11
• the Dockerfile (mostly used in MathHub) to use Java 11

[lambdaTotoro]

What else needs to be done?

[ComFreek]

I've seen Illegal reflective access by com.google.protobuf.UnsafeUtil to field java.nio.Buffer.address occurring during build. Apparently, this issue has been closed from Google's side (see protocolbuffers/protobuf#3781). Are we depending on an older version of protobuf?

Edit: Build log says:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.google.protobuf.UnsafeUtil (file:/C:/Users/ComFreek/.sbt/boot/scala-2.12.7/org.scala-sbt/sbt/1.2.8/protobuf-java-3.3.1.jar) to field java.nio.Buffer.address
WARNING: Please consider reporting this to the maintainers of com.google.protobuf.UnsafeUtil
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

Apparently, it's due to the Scala 2.12.7 dependency. Maybe increasing the Scala version (of the unmanaged libraries in deploy/lib as well) helps?

[kohlhase]

This seems almost done, targetting to release 17.
We also need to adapt https://uniformal.github.io/doc/setup/

[tkw1536]

Not sure this is doable for Release 17, re-scheduling for release 18

[ComFreek]

The latest Travis CI has been running JDK 14 to build MMT fine for several weeks. So this case is closed.