code: private static ImmutableList<String> getClassNames(String qualifiedName) {
      ImmutableList.Builder<String> classNames = ImmutableList.builder();
      List<String> parts = DOT_SPLITTER.splitToList(qualifiedName);
      for (int i = 0; i < parts.size(); i++) {
        String part = parts.get(i);
        if (isClassOrConstantName(part)) {
          classNames.add(DOT_JOINER.join(parts.subList(0, i + 1)));
        }
      }
      return classNames.build();
    }
docs: or null if no part refers to a class.