This week's giveaway is in the EJB and other Java EE Technologies forum. We're giving away four copies of EJB 3 in Action and have Debu Panda, Reza Rahman, Ryan Cuprak, and Michael Remijan on-line! See this thread for details.
Because neither the compiler nor the JVM can guarantee that the object is an ArrayList<HttpSession>, only that it's an ArrayList, you will never get this to work without a warning. So in cases like this you have to suck it up and use @SuppressWarnings("unchecked").