@NotNull @Override public Collection<String> getNonTrivialPackagePrefixes() { Set<String> names = myNontrivialPackagePrefixes; if (names == null) { names = new HashSet<>(); final ProjectRootManager rootManager = ProjectRootManager.getInstance(myManager.getProject()); final List<VirtualFile> sourceRoots = rootManager.getModuleSourceRoots(JavaModuleSourceRootTypes.SOURCES); final ProjectFileIndex fileIndex = rootManager.getFileIndex(); for (final VirtualFile sourceRoot : sourceRoots) { if (sourceRoot.isDirectory()) { final String packageName = fileIndex.getPackageNameByDirectory(sourceRoot); if (packageName != null && !packageName.isEmpty()) { names.add(packageName); } } } myNontrivialPackagePrefixes = names; } return names; }