Hey Sinjin (cool name),
I mostly agree with Max Peck. Certificates are okay and all, but I wouldn't use one as your primary education- especially one I've never heard of. Instead, go through the basic tutorials, play around with them, and see what fits into your brain and what doesn't. Then you can seek out education in the bits you struggle with.
One way to learn is by going the traditional Java tutorial route: The Java™ Tutorials
The Swing tutorial will get you started on graphics: Trail: Creating a GUI With JFC/Swing (The Java™ Tutorials)
But if you know your way around a basic Java program, and you've been doing frontend web design, you might try out Processing
, which is built on Java. It uses [mostly] Java syntax and gives you a GUI that a designer should have no trouble experimenting with- it's not going to teach you the more traditional stuff (layouts, Swing, etc), but it will introduce you to the basics in a fun way. Then from there you can start on the more traditional route of the Swing tutorials. That's just my $.02 though.
Either way, feel free to ask us questions as you go!