Or in short java isn't a tool for making games. It's a programming language. That means you have to do stuff like write code (with a text editor) and compiling it (with a compiler). It's hard but interesting work.
If you're good at it you can write a tiny game within hours. A shareware quality game takes 1-9 months... or even more. And a big mind blowing game needs a team of up to 100 people and 3-5 years... or generally spoken - twice your lifetime
If you've never used a programming language before (and it looks like that), you'll need at least 6-9 months until you can start
writing a proper tetris.
Well, maybe it's better if you just try one of those game cration tools or something like BlitzBasic
If programming is not your forte then I'd recommend you get hold of Games Factory from Click Team and pick up a copy of "Awesome Game Creation : No Programming Required" from Charles River Media.
There is also "3D Game Creation : No Programming Required" that covers 3D games using Jamagic.http://www.charlesriver.com/Books/BookDetail.aspx?productID=18866