What is greenfoot?
Consider greenfoot as a combination between a framework for creating two-dimensional grid assignments in Java and an integrated development environment (class browser, editor, compiler, execution, etc.) suitable for novice programmers. While greenfoot supports the full Java language, it is especially useful for programming exercises that have a visual element. In greenfoot object visualisation and object interaction are the key elements.
If you know BlueJ and a microworld framework (like Karel the Robot or the AP Marine Biology Case Study) consider greenfoot as the best from both: object interaction (BlueJ) and object visualisation (microworlds).
Read on for a more detailed description, or take a look at the screenshots to see what it looks like.
The Framework
The framework can be used to create a wide range of programs that can be visualised in a two-dimensional grid. Popular examples of such programs often used in an educational setting includes: The 8 Queen Puzzle, Karel the Robot, Conway's Game of Life, The AP Marine Biology Case Study and Turtle Graphics,
The framework in greenfoot has two main responsibilities:
- Make it easy to create graphical representations of objects.
- Control the execution (start, stop, step) of a simulation loop.
To accomplish these things the greenfoot framework supplies a base class GreenfootObject which should be extended by all classes that wish to visualise themselves. The two most important methods that must be implemented are the getImage() method which should return the image of the object, and the act() method which will be called in each step of the simulation loop.
When you browse the rest of this page, you will often encounter the term scenario. Scenarios are a set of classes typically created by the teacher/instructor that implements the base classes for a specific application. The idea is that the student gets an interesting framework that can be modified and extended to create even more interesting functionality. A scenario could for instance be one of the programs mentioned above. Below you can see screenshots of a turtle graphics scenario and a Karel the Robot scenario.
Turtle Graphics Scenario
Karel the Robot scenario
The integrated development environment
The greenfoot environment contains the typical elements of a development environment:
- A source code editor
- A class browser
- Compilation
- Execution control
- A debugger
In addition greenfoot can visualise the objects from a greenfoot scenario, and interact with these. It can control the execution of the execution loop of a greenfoot scenario.
The most important feature of greenfoot that sets it apart from other development environments is the direct interaction. The direct interaction is available on both classes and objects as is demonstarted below.
To instantiate a new object you select the desired method from the context menu on a class like this:
This gives you the newly created object on the mouse cursor and you can place somewhere in the world:
Objects can be interacted with in a similar manner. Invoke the context menu and select the method you want to invoke:
If the method changes a state that is visualised in the graphical representation of the object, this is imediatedly reflected:
Who should use greenfoot?
Greenfoot is aimed at programming at high school level or above (from age 13 up). It can be effectively used at school level, college and university, and even in advanced university courses.
The students at high school levels might not be as commited to programming and we have tried to create an interesting program that should engage the student. In order to do this, we acknowledge that students have different opinions on what might be interesting. Hence, we sought to create a flexible environment that could be customised for the specific group of students. Furthermore, in the design of greenfoot we considered the different learning styles of students.
The teachers/instructors in high schools can't be expected to have a lot of time and professional training, so the customisation (creation of scenarios/exercises) is made as easy as possible. In the future, we hope that many different scenarios will be available, so the teachers can just select the scenarios that best fits the students.
