Use completion settings, not Preferences
Preferences.sublime-settings was previously used for completion variables. It makes more sense to use completion.sublime-settings.
Well, no, because then you won't have .sublime-project settings respected (which are queried via view.settings()). You are correct however that it should fallback to completion settings if no view settings are set. I think a helper function is in order which pretty much does (untested) def get_setting(view, settings, key, default=[]): return view.settings().get(key, settings.get(key,default)).
Sorry for asking here, but i don't see issue category. I already installed this plugin but i don't know how to use it. I don't see any instruction. Is this plugin support autocomplete for class, method from a package jar or gradle dependency.