Using Jeroo
To Teach Object-Oriented
Concepts
By
Christian Digout
What is Jeroo?

A tool for helping students learn objectoriented concepts including:
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Instantiating and using objects
Constructors
Writing methods to extend behavior
Information Hiding
Jeroo Layout
Example of a Program
Features of the Jeroo Application
Animation showing Jeroos moving around
the island
 Source code highlighting synchronized
with execution
 Stepwise or continuous execution mode
 Choice of execution speeds
 Ability to switch between execution
modes and change speeds at will
 Error messages

Summary of Jeroo
Small Object-Oriented Language
 Only one class, the Jeroo class
 Can instantiate up to four Jeroos
 Three attributes per Jeroo

◦ location
◦ direction
◦ number of flowers
Summary of Jeroo
Six constructors to initialize the
attributes
 Seven action methods
 Seven sensor methods to examine the
immediate surroundings
 Four relative directions

Instantiation
The process of creating an instance of an
object.
 Jeroo has 6 constructors

◦ Including a default constructor
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The new operator is used to instantiate
objects
Constructors
Objects and Jeroo

States (or member variables)
Position (x, y)
Direction (North, East, South, West)
Number of flowers
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Information Hiding
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◦ A Jeroo’s data is protected
◦ Protects data integrity
◦ Need to use member methods to access member
variables
Behavior and Member Methods
Behaviors and Member Members
Student Assignments

From the Jeroo website:
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Pick All Flowers
The Maze
Walk the Lake
http://home.cc.gatech.edu/dorn/48
Jeroo
Use of constructors
 Get use to the dot-notation
 Use member methods
 Can extend the Jeroo class with new
methods

Java – Building a Class
public class Circle {
private static final double PI = 3.14;
private double radius;
public Circle() {
radius = 1;
}
public void setRadius(double newRadius) {
radius = newRadius;
}
}
Jeroo Class
It is written in Java
 Ask students what would it include?
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◦ 6 constructors
◦ Member variables
◦ Member methods
Turtle Graphics
Downloaded from:
 http://www.cengage.com/cgiwadsworth/course_products_wp.pl?fid=M
20bI&product_isbn_issn=9780619267230
 Part of textbook resources for:
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◦ Fundamentals of Java by Lambert/Osbourne
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Allows students to create simple graphics
using Java
Turtle Graphics
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Good for showing:
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Composition “has a” relationships
Inheritance “is a” relationships
Interfaces
Abstract classes
Turtle Graphics
Create a Shape Interface
 AbstractShape can implement Shape

◦ Can implement members that would be the
same for all shapes such as:
 X and Y coordinates
 Move function
◦ Abstract methods would be:
 Area
 Draw
Shape Hierarchy

Can implement Circle and Rectangle
Classes with students.
◦ Extend Abstract Shape
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Assignment:
◦ Students implement a Triangle Class
◦ Students can add a Perimeter Method to the
hierarchy