I've never found GUI builders to be very useful in Java anyway. NetBeans has a very good one, but I highly recommend you build your own GUIs.
On the other hand, you may find Swing GUis somewhat verbose. There are alternatives, Java-FX apparently has a declarative language that you can define your GUI in while writing everything else in Java.
Also Groovy has a nice declarative syntax layer over Swing that can make things a little easier when starting out.
If you want to experiment with Swing, I recommend playing with it in Groovy or BeanShell. It's a real quick to just type:
f=new JFrame("My Frame")
f.setVisible(true)
f.setSize(300,600)
and see your frame show up on the screen. (Both Groovy and Beanshell handle Java syntax very well--it's not like you are not learning Swing--it's more like you are learning it in an interpreter instead of compiler...
By the way, if you don't want to use Java's syntax Groovy can make it easer with statements that are SOMETHING like this (I may have it wrong by just a tad)
f=new JFrame(name="My Frame", visible=true, size=[300,600])
which changes it from 3 or 4 lines down to one.