Java is a great language. You can branch out and go into many areas with it.
Since you already have a little bit of programming experience, but lack object oriented concepts you should use these three books (in order):
1. Thinking in Java [3rd edition], Bruce Eckel. The third edition is available at Amazon. Alternatively, he offers the second edition FREE on his website:
http://mindview.net/Books
This book will give you a good rundown of object oriented principles and how to apply them in Java. Its a very popular book.
2. The Java Programming Language [4th edition], Ken Arnold, James Gosling, David Holmes. A great reference book. I have my copy nearby [3rd edition] and use it all the time. James Gosling (one of the authors) is the guy who developed the Java language. So, it should go without saying, that this is a good resource
3. Effective Java Programming Language Guide [1st edition], Joshua Bloch. A great book on how to write good Java code. Many of the tips in this book you will learn over time on your own, but some of the ones you wouldn't naturally incur or think about are worth the price. If you want to get up to speed on writing decent code, buy this book after you've used the first two. Read it a couple months into your Java adventures. Then continually reread it every couple months. Its a rather short book and very useful.
Thats all you need to know to learn Java for now. Once you are knowledgeable with the language you can branch off into graphics toolkits, enterprise web apps with J2EE, portable apps with J2ME, etc. Once you develop a strong Java foundation the rest of these are easy to pick up on.