ACS-1903
Lab 2: Objects, Scanners, Numbers
Fall 2007
Working with Objects, Scanners, Numbers
In Lab 2 we will work with the same shapes classes as in Lab1, but we will interact with
them programmatically using main() and appropriate messages.
In this lab you will :
 Review the shapes classes: Circle, Square, Triangle
 Write classes with main() methods that interact with shapes objects
The lab demonstrator will initial your lab appropriately in the spaces provided, and when
you are finished, hand the lab in to your demonstrator.
Student Identification
Student number
____________________________________________
Last name
____________________________________________
First name
____________________________________________
Workstation user id
____________________________________________
Email address
____________________________________________
1.
Logon to your workstation
Using your userid and password from Lab 1, logon to a workstation.
Obtain the Java files
Begin with the same Java classes as in Lab1. If necessary you can download the four java
files from http://io.uwinnipeg.ca/~rmcfadye/1903/shapes/.
Start BlueJ
Create a BlueJ Project
Create a project. It can be useful to you if you store such a project on the H drive. You
have access to this drive from both computer labs.
Import java files
If necessary, import the four java files to your project
Review the Triangle, Circle and Square classes
Use Tools >> Project Documentation to review the methods/responsibilities of these
classes.
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ACS-1903
Lab 2: Objects, Scanners, Numbers
Fall 2007
2. In Lab 1 you determined how to arrange for a square to be immediately below a
triangle. Now do this programmatically using a main() method.
Your main() method must:
 Instantiate a triangle,
 Instantiate a square,
 Make the triangle visible
 Make the square visible
 Send one or more move messages to the triangle and/or square
The following code may prove useful to you; it does all but the movement. You can
create a new class in your project named drawPicture, paste the following in it, test it and
develop it further.
public class drawPicture
{
public static void main()
{
Triangle t;
Square s;
t = new Triangle();
s = new Square();
t.makeVisible();
s.makeVisible();
// place one or more move messages here
}
}
Note that when testing your program (modify and recompile), you may need to reset the
Java Virtual Machine.
When you have drawPicture working correctly you must show it to the lab
demonstrator.
Demonstrator’s initials:
2
ACS-1903
Lab 2: Objects, Scanners, Numbers
Fall 2007
3. Note that each of Triangle, Square, Circle have methods to move horizontally and
vertically a number of pixels:
public void moveHorizontal(int distance)
public void moveVertical(int distance)
Write a class named moveObjects with a main method that uses the Scanner class and the
nextInt() method to accomplish:
 prompt for a horizontal distance and send moveHorizontal() to a square
 prompt for a vertical distance and send moveVertical() to a square
 prompt for a horizontal distance and send moveHorizontal()to a circle
 prompt for a vertical distance and send the moveVertical()to a circle
 prompt for a horizontal distance and send moveHorizontal()to a triangle
 prompt for a vertical distance and send the moveVertical()to a triangle
You may find the following code a useful starting point.
import java.util.Scanner;
/**
* Moving shapes objects left/right and up/down
*
* @author (your name)
* @version (a version number or a date)
*/
public class moveObjects
{
public static void main()
{
Square s;
s = new Square();
s.makeVisible();
System.out.println(
"How many pixels should I move the square?");
Scanner keyboard = new Scanner(System.in);
int moveSquareHorizontal = keyboard.nextInt();
s.moveHorizontal(moveSquareHorizontal);
}
}
Note that when testing your program (modify and recompile), you may need to reset the
Java Virtual Machine.
When you have moveObjects working correctly you must show it to the lab
demonstrator.
Demonstrator’s initials:
3