Introduction To
Greenfoot
Part-2
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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 http://www.greenfoot.org
 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 (http://kakihijau.googlepages.com).
Introduction to Greenfoot 2
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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,
http://www.greenfoot.org
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Outline
 Class Display Revisited
 Class Editor
 The Leaf Class
 The Wombat Class
 The WombatWorld Class
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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)
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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“
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Class Editor (2)
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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
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The Wombat Class (1)
import necessary packages
class header;
Wombat is a subclass
from Actor
data (constants and
variables)
class constructor and
methods
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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()
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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
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The Wombat Class (4)
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The Wombat Class (5)
this method is inherited from
the superclass Actor
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The Wombat Class (6)
change direction 90 degrees
to the left
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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
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The Wombat Class (8)
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The Wombat Class (9)
if object reaches one of
the borders, do nothing!
the object moves setLocation() is
forward; inherited from Actor
depends on
its direction
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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!
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The WombatWorld Class (1)
 1 constructor : WombatWorld()
 2 methods :
– populate()
– randomLeaves()
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The WombatWorld Class (2)
calls the World constructor
sets the background.
the method is inherited
from the superclass World
cell.jpg
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The WombatWorld Class (3)
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The WombatWorld Class (4)
Create a Leaf object at a random
position (x,y); repeat howmany
times
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