public Comment addComment(int messageId, Comment comment) {
   String query =
       "insert into comment (\"commentMessage\", author, created, \"messageId\") values('"
           + comment.getCommentMessage()
           + "', '"
           + comment.getAuthor()
           + "', '"
           + comment.getCreated()
           + "', "
           + messageId
           + ")";
   db.addData(query);
   return comment;
 }
 public Comment updateComment(int messageId, Comment comment) {
   String query =
       "update comment set \"commentMessage\" = '"
           + comment.getCommentMessage()
           + "', author = '"
           + comment.getAuthor()
           + "', created = '"
           + comment.getCreated()
           + "', \"messageId\" = '"
           + messageId
           + "' where id = '"
           + comment.getId()
           + "'";
   db.addData(query);
   return comment;
 }
 public Comment removeComment(int commentId, Comment comment) {
   String query = "delete from comment where id = '" + commentId + "'";
   db.addData(query);
   return comment;
 }