anonymous wrote : Being dependent on the implementation in one place (at construction) is better than being dependent on the implementation in N places (each place the class is used), so it's an improvement. I agree, but that is what IOC is all about, it class doesnt have to worry about how a pluggable component is constructed. anonymous wrote : 1) Makes testing a whole lot easier since can easily create mock / fake implementions i agree anonymous wrote : 2) Makes code easier to read / understand again i agree anonymous wrote : 3) If user wants to create their own implementation of the interface they can. If it's a concrete class they'd have to extend that class. That may not be possible or desirable. defo. I'm not against using interfaces where we can, just making a point. We have to make sure that we dont just introduce interfaces that are dragged out of the implementation, the abstraction still needs to make sense. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4132492#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...