nb-javac is used internally by NetBeans to decouple the runtime JDK version from editor capabilities. This allows NetBeans to use the latest upstream javac without having to run on the latest JDK.
nb-javac is currently built from
https://github.com/JaroslavTulach/nb-javac
and available on maven central
https://mvnrepository.com/artifact/com.dukescript.nbjavac/nb-javac