This is a milestone release, offering a technology preview of new features, and the opportunity to participate in the community testing of GeoServer Java 11 compatibility:
binary distribution is ready Java 8 and Java 11 support
WAR distribution requires Tomcat 9 to work on Java 11
Help test additional platforms and will will update our user manual
If you are currently using Oracle JDK now is a good time to consider your options, ask questions, and lend us a hand testing GeoServer on Java 11. Our goal is to support GeoServer on both Java 8 and Java 11 giving everyone a chance to migrate when they are ready.
We have been planning Java 11 compatibility for some time with the end-of-life of Oracle Java 8 scheduled for January 2019. Fortunately the Java industry has mobilized with RedHat OpenJDK offering to back port changes, and industry players getting behind Adopt OpenJDK to distribute these fixes to other platforms.