public ArrayList<UserComment> retrieveEntryComments(String userId, long partId) { Entry entry = dao.get(partId); if (entry == null) return null; authorization.expectRead(userId, entry); // comments ArrayList<Comment> comments = commentDAO.retrieveComments(entry); ArrayList<UserComment> userComments = new ArrayList<>(); for (Comment comment : comments) { userComments.add(comment.toDataTransferObject()); } return userComments; }