Migrating from Java 8 to 11

[GHPS]

PixelController runs fine under Java version 8 (java8). Since the
official date for End-of-Life is getting closer (in parts already past) it's
not a bad idea to update to Java 11. Starting PixelController with Java 11
one unfortunately gets the error message

[0,576s][info][class,load] java.util.IdentityHashMap$KeySet source: jrt:/java.base
java.lang.ClassCastException: java.base/jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to java.base/java.net.URLClassLoader at org.appstart.Starter.main(Starter.java:74)

Not only for a Python programmer this is rather cryptic - even from a Java
perspective the problem seems to be quite hard to fix [1]. While many
projects stick to Java 8 in face of upgrade problems [2] the question
nevertheless arises:

Has anyone succeed in converting PixelController to Java 11?

1: https://community.oracle.com/thread/4011800
2: https://www.theregister.co.uk/2019/03/07/java_developers_version_8/

[neophob]

note: i dont maintain this project anymore but happy to merge prs.

[GHPS]

note: i dont maintain this project anymore but happy to merge prs.

Great - the latest commits (b39c05d and 94b02e5) were made to
the 'master' branch but not to 'develop'. Moreover 'develop'
contains the latest release version '2.1.0-RC1' which contains
features not implemented in 'master'. Now - almost 5 years after
the release - RC1 can safely be renamed to '2.1.0'.

Therefore I suggest merging the latest 'develop' branch into
'master' and call it version '2.1.1' since some minor issues
have been fixed.

This would make the future development of PixelController much
easier.