I'm not sure, but I think this is the same doubt that I was having with Eclipse and ppl from greenfoot (i think) discussed it here. I'm just answering this post cause I want help on that too :D...

In Greenfoot, if you go to Edit menu, then Preferences, there is a Libraries tab. From there, you can add JARs or directories (with .class files in them) to the Greenfoot classpath for all scenarios. That should allow you to use external Java code from within Greenfoot. Meanwhile, what I think giordanno92 is referring to is using the Greenfoot libraries from Java code developed and run outside Greenfoot, which is not practically feasible, and not something we are likely to support.

Yeah, looking now I think I've misunderstood the doubt of the topic, cause I've already seen something about BlueJ and NetBeans on the java site (i think), so I thought that was the question... I'm really hoping Greenfoot can reach the IDE level of NetBeans and Eclipse about make coding easier. But I can't help myself about how faster I can code with those IDEs, sorry for any inconvenience.

Thanks nccb! That should work well enough. It's too bad the setting is Greenfoot-wide rather than being a per-project setting. If it were a property of a Greenfoot project (scenario) then we could just bring in the pieces we need for each individual project. This casts the net a bit wider than necessary, but it will still work.

giordanno92, the method described in this topic can kind of help you accomplish what you want. We've used Netbeans to create a utility library for managing high scores. (Okay, really it was to learn Java I/O, but it has a use.) It was easier to do in Netbeans and it helped my students to expand their understanding. Then we will link back to these classes, as described in this topic, and use them in Greenfoot scenarios. Structure your code in such a way that you can separate out parts that require Greenfoot and parts that don't. Greenfoot makes some things really easy. In other places, it just doesn't have the sophistication of a full IDE. Use different tools and environments for their different strengths. Besides, it's generally a good idea to structure your code to decrease dependencies. It's generally a good idea to separate UI code from the real logic of your program. The Greenfoot classes are basically UI components. If you have a Monster (class) which is an Actor and the Monster has lots of logic, then you could create a MonsterEntity (or better name). Then the Monster could have a MonsterEntity and pass off to it all of the "heavy lifting". Basically, anything which does not extend a Greenfoot class or call something in a Greenfoot class could be implemented in Eclipse or Netbeans and used in Greenfoot. (Such as Vector.) If you do develop utilities or logic classes in Netbeans or Eclipse, write unit tests to make sure those classes work before you start using them in Greenfoot.