Don't kid yourself: that's coupling

One of the books that I was reading (I think that it was Lighter, Faster Java) was talking about coupling. When working with a language like Java, it's a good idea to try and deal with interfaces instead of concreate classes. Especially with method signatures. But that's another rant about the joy's of the Java Collections.

Back on topic. Working with interfaces is a good idea, just don't kid yourself when you are doing it. For example, if you have some code like this:
Set mySet = new HashSet();
it is no less coupled to HashSet than code that is written like this:
HashSet mySet = new HashSet();

So, using interfaces in method calls / signatures: good. Using interfaces where you create a new concreate object (not using a factory or something like that): pointless.