Look, there are numerous tools out there ranging from free to affordable to expensive to make Java GUI painless. Once used you can study the generated code to see how it's done:
Netbeans - A full featured, cross platform, Open Source Java IDE w/ a nice GUI designer including Gridbag Layout. Very mature robust product. Written in Java it requires a fast computer to appreciate (600mhz +, 128MB RAM +, 3D graphics card)
Borland JBuilder (Foundation Edition) - Powerful, fast, full featured Java IDE and GUI Designer.
Elcipse - Full featured Java IDE, but no built in GUI designer. Not as mature as Netbeans or JBuilder, but improving in leaps and bounds. Faster than Netbeans, but slower than JBuilder. GUI designers for eclipse can be purchased from 3rd parties.
Swing designer - $199.00 a Java GUI editor plug-in for Eclipse. Really sweet GUI layout tool capable of rapid development of complex GUIs in Swing or Eclipse's SWT and the code it generates is professionally formatted, readable, and easy to maintain.
Borland JBuilder (Developer Edition) - $499 Top of the line Java IDE, GUI Designer, and Rapid Database Developer.
BX for Java - $998 a complete stand alone visual development tool for pure Java applications. Includes a database designer module that makes Java widgets "data-aware" by mapping them to database fields.
Hope this helps,