* The interface implemented and exposed by the builder
* @author <a href="mailto:bombe@pterodactylus.net">David ‘Bombe’ Roden</a>
*/
-public class AbstractReplyBuilder<B extends ReplyBuilder<B>> implements ReplyBuilder<B> {
+public abstract class AbstractReplyBuilder<B extends ReplyBuilder<B>> implements ReplyBuilder<B> {
protected final String senderId;
protected Optional<String> id = absent();