@Override
  public @Nullable String getErrorMessage(@Nullable Project project, @NotNull String className) {
    if (!PsiNameHelperImpl.getInstance().isQualifiedName(className)) {
      return JavaBundle.message("validator.text.not.valid.class.name");
    }
    if (project == null) return null;
    //wait for loading
    if (project.isDefault() || DumbService.isDumb(project)) {
      return null;
    }
    GlobalSearchScope scope = GlobalSearchScope.allScope(project);
    PsiClass psiClass = JavaPsiFacade.getInstance(project).findClass(className, scope);
    if (psiClass == null) {
      return JavaBundle.message("validator.text.class.not.found");
    }
    return checkClass(psiClass);
  }
@Override
  public @Nullable String getErrorMessage(@Nullable Project project, @NotNull String className)