How not to check for null

There are some clever tricks how to deal with null values. Usage of guava's Optional is one of them. But this is not one of them:

    final Optional<MilestoneDocument> documentOfVersion = findDocumentOfVersion(documentType, documentVersion);
    if (documentOfVersion == null) {
      throw new IllegalStateException();
    }
    if (documentOfVersion.isPresent()) {
      return documentOfVersion.get();
    }