Исправление Deleted, (текущая версия) :
и они форкнули javac https://blogs.apache.org/netbeans/entry/what-s-nb-javac-in
So, as can be seen, from Apache NetBeans running on JDK 9 and onwards, you have a choice: either use the Java compiler from the JDK, which means you're not benefiting from a number of enhancements especially added for NetBeans over many years in the patched Java compiler, or you need to explicitly add the patched Java compiler, since it is provided by Oracle and its licensing is such that you need to take responsibility for installing it yourself. On the other hand, if you're using Apache NetBeans with JDK 8, the choice is simpler, i.e., you need to install nb-javac, otherwise you will not be able to use Java in Apache NetBeans.
It's not an ideal situation. On the other hand, if someone has a better solution, please feel free to propose that solution and also consider providing a pull request too!
Исходная версия Deleted, :