Dynamic class diagrams in JAKE

It’s been noted [e.g. 1] that showing the static class structure is important in teaching materials and tools. BlueJ, for instance, places a lot of emphasis on this.
The JAKE IDE dynamically compiles a class diagram as classes are added to the JAKE program. Every program starts with a default class diagram that shows all the classes in the main JAKE package: World, Mover, Robot, and so on.

Debugging: Class, interface, or enum expected.

Java's error messages aren't always very meaningful - to novices at least. Take this, what we might imagine to be a fairly common error:

Class, interface, or enum expected.

Now, I know what it means, but would a new programmer? To understand this message, you surely need to know what an interface or an enum is - neither of which are likely to be taught in the first few lessons.

New robot graphics

Up until now Jake's had to make do with a clipart-based outfit. His new ensemble has now arrived, and it comes in several stylish colours...

The new drawings are courtesy of Miriam Lowrie.

Ghosts!

JAKE is an objects-first tool, built using the object-oriented Java language.
One of the advantages of using robots is that there's a clear model for inheritance. In the current build, the JAKE architecture has a number of classes. The World owns several WorldObjects. There are different kinds of world object: Walls, Beepers and Movers. Walls are solid structures that block off paths in the World. Beepers are just that - little devices that "beep" so that they can be detected by the robots. For now, Movers are the most interesting class.
Just like there are different kinds of WorldObject - one of which is the Mover - there are different kinds of Mover. All Movers can, well, move. Different kinds of Movers behave in different ways, but all have a move() method. The first type of Mover to be created was the Robot. The Robot class represents a basic robot that can move forwards, turn, and do some other (similarly exciting) things. Jake - our main character - is one of these Robots.

It's alive!

The robot has a name: Jake. Jake stands for "Java Karel with Events". Jake is based on Karel the robot, with an objects-first approach and some new button-based event interfaces.

Today the first prototype is complete: Jake can move, turn and bump into walls. He's programmable in Java using the "jaketherobot" package. There are world, robot, beeper and wall classes.

So far Jake only exists as a collection of classes. The JAKE IDE is planned for development within the next couple of months.