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.
It means that aset is a HashSet<Character> variable which isn't initialized, and bset is a HashSet<Character> variable which is initialized to refer to a HashSet<Character> object. It's nothing to do with generics; consider this: