Assignment Four

Lab assignment:

Create a class called Rectangle that has functionality like Circle. You are given RecDemo, a very simple demonstration program. Examine the code in RecDemo and make a Rectangle class that will perform the necessary functions. Hints: My version has... 4 private instance variables (all floats) 3 public final static (class) variables (all ints) 1 instance of the Rectangle class 2 static (class) methods for calculation 3 constructors (2 doubles, no parameters, one int) 4 double getters 1 String getter 2 setters no event handling Comment out most of the code in the init method of RecDemo. Uncomment just a small part at a time, and implement that part in Rectangle. When it is working, move on to the next part. For example, I started by testing only the two double constructor and the String getter. When I got that working, I uncommented the code for the next constructor in RecDemo, then built the code for it in Rectangle. When I had this adequately tested, I moved on. Suggested order of implementation

Get the 'two double' constructor, static calc methods, and getValues getter done first.
Then do the 'no parameter' constructor and the code that demos it.
Next do the 'one int' constructor, its associated static final variables

You will need to recompile both classes whenever you make a change. The final output ought to look something like this:

Here's the code for the RecDemo class. Feel free to just copy and paste it into your editor.


//RecDemo
//used to demonstrate Rectangle class
//By Andy Harris, 5/11/97

import java.awt.*;
import java.applet.*;
import Rectangle;

public class RecDemo extends Applet{

  Rectangle myRec;  

  public void init(){

    //test '2 double' constructor and getValues
    myRec = new Rectangle (3d, 5d);
    add(new Label(myRec.getValues()));
    
    //test 'no parameter' constructor
    myRec = new Rectangle ();
    add(new Label(myRec.getValues()));

    //test 'one int' constructor
    myRec = new Rectangle (Rectangle.SMALL);
    add(new Label(myRec.getValues()));
     
    myRec = new Rectangle (Rectangle.MEDIUM);
    add(new Label(myRec.getValues()));
     
    myRec = new Rectangle (Rectangle.LARGE);
    add(new Label(myRec.getValues()));
    
    
    //test static methods
    String outString = new String();
    
    outString = "Perim of 5,6: ";
    outString += String.valueOf(Rectangle.calcPerimeter(5d,6d));
    add(new Label(outString));

    outString = "Area of 5,6: ";
    outString += String.valueOf(Rectangle.calcArea(5d,6d));
    add(new Label(outString));

  } // end init
  
} // end class def

Here's a link to the same file if that is easier for you.

© Andy Harris
Indiana University / Purdue University, Indianapolis
email: aharris@cs.iupui.edu
homepage: http://www.cs.iupui.edu/~aharris