1. Introduction To Greenfoot
Part-2

2. Disclaimer
This document is intended to give a beginner an introductory material for the Greenfoot system. Greenfoot is a software framework made by Poul Henriksen and Michael Koelling at University of Kent / Deakin University. More information can be found at
This document is available „AS IS“ free of charge for personal use and non-commercial redistribution. It may not be sold for profit or included in other packages which are sold for profit without written authorisation. This document is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; your use of the document is at your sole risk. Reusing and modifying (part of) this document is allowed, as long as you state explicitly that your work is based on the original document produced by the copyright holder: Eueung Mulyana. The author can be contacted via eueung-[at]-yahoo.com (

3. Purpose
This is the second part of the document „Introduction to Greenfoot“ and focuses on understanding the wombats scenario
Part of the content of these slides is based on the Greenfoot Tutorial made by Michael Koelling, publicly accesible at the Greenfoot website,

4. Outline Class Display Revisited Class Editor The Leaf Class
The Wombat Class
The WombatWorld Class

5. Class Display Revisited
Class display contains all classes which are used in a scenario
Class World and Actor are abstract superclasses, part of the Greenfoot system
Scenario wombats has 2 actor classes (Wombat, Leaf)

6. Class Editor (1)
We can modify objects behaviour by editing the source code of the corresponding class
To display the source code editor:
Double-click the class
Right-click the class, choose the item „Open editor“

7. Class Editor (2)

8. The Leaf Class
The simplest class compared to the Wombat and WombatWorld class
Leaf objects do nothing!
As you can see in the previous slide, the Leaf class has no statement and consists of an empty constructor

9. The Wombat Class (1) import necessary packages class header;
Wombat is a subclass
from Actor
data (constants and
variables)
class constructor and
methods

10. The Wombat Class (2) 4 constants : EAST, WEST, NORTH, SOUTH
2 variables : direction, leavesEaten
1 constructor : Wombat()
8 methods :
getLeavesEaten(), foundLeaf(), eatLeaf()
setDirection(), turnLeft()
canMove(), move()
act()

11. The Wombat Class (3) constructor  initialising
direction and leavesEaten
is there any Leaf object
in my position?
this method is inherited from
the superclass Actor
remove that Leaf object
update the variable
leavesEaten

12. The Wombat Class (4)

13. The Wombat Class (5) this method is inherited from
the superclass Actor

14. The Wombat Class (6)
change direction 90 degrees
to the left

15. The Wombat Class (7) these methods are inherited from Actor
new coordinate
if the object moves
forward;
depends on
its direction
checks if the object
reaches the edges of the world

16. The Wombat Class (8)

17. The Wombat Class (9) if object reaches one of the borders, do nothing!
the object moves
forward;
depends on
its direction
setLocation() is
inherited from Actor

18. The Wombat Class (10) if you find leaves, eat !
if you don‘t find leaves, but you can move forward, then move!
if you don‘t find leaves and you also cannot move, then turn to the left!

19. The WombatWorld Class (1)
1 constructor : WombatWorld()
2 methods :
populate()
randomLeaves()

20. The WombatWorld Class (2)
calls the World constructor
sets the background.
the method is inherited
from the superclass World
cell.jpg

21. The WombatWorld Class (3)

22. The WombatWorld Class (4)
Create a Leaf object at a random
position (x,y); repeat howmany
times