hi,
if your layout management works fine, use pack() and let the components compute their preferred size (of course
you should set the preferred size of tables, trees etc.). pack() should be called instead of setSize() (it will overrule setSize if called afterwards, or setSize will overrule pack() in the opposite case), after adding all components, and before calling setVisible().
if you use >1.4 you can place the frame in the center of the screen by calling:
frame.setLocationRelativeTo(null);
(this is a method of java.awt.Window)
regards,
Chantal