How I got good with Java

I started with Java programming from making Minecraft mods, using Eclipse, and MCP (Minecraft Coder Pack). The coder pack decompiles and deobfuscates the jar (only unmodified jars), and when you're done modifying the source, it will recompile it into .class files, which you can add to your jars. It's very easy, and it's good for those people that learn by doing things.
Minecraft Coder Pack
Eclipse