In a session Thursday afternoon, Michael Kölling and John Rosenberg demonstrated BlueJ, a Java IDE they had developed over the last seven years for teaching O-O programming.

BlueJ's guiding philosophy is to make it possible to teach object-oriented concepts first, before students even begin to write code. It does so by representing the objects in a UML-like graphical format, and showing their instances as boxes on a tray at the bottom of the screen. Clicking on an instance brings up a list of its methods, which may be executed directly. The result is so stunning that, once you see it demonstrated, you wonder how we could ever have taught programming any other way.

BlueJ has been adopted by at least 500 schools. In fact, since they usually have no way of knowing when it has been adopted, the number may be much higher. Kölling and David Barnes have authored an excellent textbook: Objects First with Java: A Practical Introduction using BlueJ (PrenticeHall 2003).

BlueJ is free (as in free beer) to use for use in schools or businesses, or for any other purpose so long as it is not resold. It can be downloaded from http://www.bluej.org/ It is not open source -- specifically , as they explained, to prevent folks from adding their favorite improvements and spoiling its zen-like simplicity in the process. But don't go off to teach Java without it!