faurek:
I´m learning BASIC for programing AVR chips on school, and I was interested on learning Java too.
Let me give you an analogy ...
Let's say you are planning to visit Russia, and you don't speak Russian. It would be logical to learn Russian, right? But a friend says "why not learn Greek? - some people in Russia speak Greek". Now you could do that, and it would work in a limited sort of way. But learning Russian is smarter, yes?
The fact is that 99% (if not 99.9%) of programs for the Arduino are in C++. That isn't a particularly hard language to learn. Almost all of the libraries, example code, projects, etc. are in C++. That is the "native" programming environment. Yes, I know you can turn Basic into .hex code if you find a compiler, but where would that be?
If you choose to go down the Basic route, you have abandoned most of the examples, help, libraries, etc. that you will get if you stick to the language used by the Arduino IDE. Even the examples in the Atmel datasheet are in C (and machine code).