This week's book giveaway is in the General Computing forum. We're giving away four copies of Arduino in Action and have Martin Evans, Joshua Noble, and Jordan Hochenbaum on-line! See this thread for details.
There is no difference in performance. A Java import only comes into play at compile time, and then ONLY the required classes are pulled in. This makes it somewhat different from a C++ include which pulls everything in. With that said, for production classes many shops insist that you name the exact classes that you want imported for documentation purposes.
"JavaRanch, where the deer and the Certified play" - David O'Meara
Please don't post the same question in multiple forums. It takes time for people to answer, which is wasted if the poster doesn't realize the question has already been aswered elsewhere. Followups can go here. Thanks.