I've always liked to point out that the Input''''''Stream hierarchy in Java (yes, it's JDK 1.0, but it's still there...) is an example of the DecoratorPattern.  Specifically, all Input''''''Streams are either leaves (e.g. File''''''Input''''''Stream, String''''''Buffer''''''Input''''''Stream) or Decorators (e.g. Filter''''''Input''''''Stream and its subclasses).  In fact, this hierarchy nicely shows all three ways in which Decorators can extend their "Wrapped" objects, e.g by additional state (Line''''''Number''''''Input''''''Stream), additional methods (Pushback''''''Input''''''Stream) or extended core methods (Buffered''''''Input''''''Stream).

KyleBrown