Have you tried looking at the
java documentation for instanceof?
Maybe a google search? The top entry on my google search just came back with an interesting discussion on the sun java forums.
Basicly, it does what it says. It returns true is objectB is an instance of objectA.
Upcasting simply means you are casting the object "up" the inheritance tree. If you are having trouble with this, I really do suggest you go to the Java site and read up on Object casting, it is a fundemental concept.
Give C extends A, and B extends Object, what do you think the result of these would be?
Gavin