How should I start? | Java the Devil |

Hi everyone!
I assume that this isn't a good place to get advice, but it could be.
Anyways, I've been wanting to learn how to make plug-ins (or coding in java)
But, I'm not sure where to start. I can't even decompile/recompile a file on this computer, and I'm not sure on what program can.
Can I get a few bits and pieces of advice to perhaps make my learning easier?
I do plan on purchasing a reference book on java, whenever I can locate one that is.