What was Duck Typing again?

Duck Typing is a powerful feature included primarily in newer languages. It provides the following capability: An object having all the methods described in an interface can be made to implement that interface dynamically at runtime, even if the objects class does not include the interface in its implements clause.
This is actually a somewhat restricted definition of Duck Typing compared to other languages. But it is the one I have chosen because it is the one I believe fits best with Javas design philosophy of having API contracts explicitly specified in interfaces up-front.
The good news is that although this feature is not built into the Java language, it turns out to be quite easy to implement.