See issues fixed from a complete list of issues that is done for the 8.4 (rc1) release
Minimum Java version is from 8.4 on Java 8
Java 11 support (for developer, war/app server should already work)
Many Java Libraries are updated, some from the updated eclipse (4.8 (needs java 8))
Logging libraries are updated to Log4j2, now using a separate file log4j.xml for configuring the logging.