This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
You are not allowed to place assignments (=) in if statements. You are only allowed to make comparisons in if statements (==) and call methods that return boolean. This is a Java build-in security checking mechanism.