The problem with adding block calls to the listener are that it is a specialised callback that serves little general purpose use. The problem with a sub-interface is that it adds complexity and a performance bottleneck to the notifier (the need to test each listener if it is a subclass instance, etc). If at all I'd prefer the 2nd approach, so we could even move viewChanged() to the 2nd interface - perhaps ReplicatedCacheListener with viewChange() and block/unblock events. Thoughts? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4053631#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...