This week's book giveaway is in the Agile and Other Processes forum. We're giving away four copies of Darcy DeClute's Scrum Master Certification Guide: The Definitive Resource for Passing the CSM and PSM Exams and have Darcy DeClute on-line! See this thread for details.
In the first case, you are casting, however in the second, you are calling a method on a variable that is null. Hence, the reason for the null pointer. With casting, if what you are casting returns null, your fast will return exactly that.