This week's book giveaway is in the Performance forum. We're giving away four copies of The Java Performance Companion and have Charlie Hunt, Monica Beckwith, Poonam Parhar, & Bengt Rutisson on-line! See this thread for details.
If you want to set the preferred size, every get method usually has a corresponding set (i.e. setPreferredSize(java.awt.Dimension)). If you want to override getPreferredSize, you'd have write your own class to extend JTextField.