This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
You cannot use identifier syntax with super. You can only use ? with super.
The reason for this is that since you don't know what type it actually is, so you can't declare a name for it. Suppose you were allowed to do this
<T super Integer>
now what. What does T stands for?? It can be Number, Object, Comparable, Serializable (these are all super-types of Integer). So you are not sure what it actually is. So you cannot create instances of T as
as you don't know the actual type of T. This is why you have to use the ? syntax.
Now you may ask why is this allowed for extends syntax.
<T extends Number>
In this case you at least know that T supports the functionality supported by Number. So you can say that yes, I can call intValue or shortValue on any object created of type T (as these methods are defined in Number). This is why identifier syntax is supported with extends but not super.
It didn't used to make sense for me either. I used to fear from Generics. Then everyone at ranch gave me the confidence that I can do it. I used generics tut from sun to get comfortable with Generics...