final ObjectSet<DownloadedMessageLink> messageLinks = new Persistent.InitializingObjectSet<Board.DownloadedMessageLink>(mFreetalk, q);
switch(messageLinks.size()) {
case 0: throw new NoSuchMessageException("index: " + index);
case 1: return messageLinks.next();
default: throw new DuplicateMessageException("index: " + index);
}
}