Elytron currently has a minimum build JDK of 11. A few modules list older versions and likely can be upgraded. Here's a list of modules that appear to be affected:

• wildfly-elytron (1) (Security SPIs)
• wildfly-elytron-security-manager
• wildfly-elytron-ssl
• wildfly-elytron-tool
• wildfly-elytron-tests

It likely also affects the parent package (and all submodules as a result), where the maven-compiler-plugin is currently configured to target Java 8.

A side effect of this issue is that IntelliJ IDEA uses the configuration of the maven-compiler-plugin to determine the project language level. Updating the parent POM should correctly configure all submodules which don't explicitly declare the build version.