private void checkInterface(PsiClass aClass) {
      final PsiReferenceList extendsList = aClass.getExtendsList();
      if (extendsList == null) {
        return;
      }
      final PsiJavaCodeReferenceElement[] extendsElements = extendsList.getReferenceElements();
      for (PsiJavaCodeReferenceElement extendsElement : extendsElements) {
        checkExtendedInterface(extendsElement, extendsElements);
      }
    }
private void checkInterface(PsiClass aClass)