Hi,
first of all, thank you very much for developing devstyle!
When I open a Java file which is not located in any of the projects in eclipse (but does have .java file extension and has valid java code) the syntax highlighting does not seem to work properly.
I have also encountered this problem (but cannot replicate it right now) with files which were part of the projects, i think it had to do with the nested maven projects i had. For example, when i searched for a class via CTRL+SHIFT+T, eclipse always shoed me multiple results of the same file but with different folders (which had to do with the nested/multi module maven projects).
Anyways, what happens is that if this error occurs only a basic highlighting is applied. See this screenshot, on the right is a copy of the file on the left, which is saved outside of the eclipse projects:
Highlighting problem
I am currently using eclipse 2019-03 but the error also occurs with eclipse 2018-12. Latest devstyle version.