This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
The only way this might be possible is to implement WindowListener on your JFrame and then in the windowMaximized(WindowEvent w) method adjust the verticle of your JFrame to not change. The problem with this is you are going to see the JFrame maximize in both directions and then see the height change after that.