Project6

Computer Science 111 Introduction to Algorithms and Programming: Java

Programming Project #6   Polymorphism & Inheritance (30 points total)

For project #5 we will implement a classic Inheritance hierarchy and implement a little polymorphism. Build your classes first, each in their own .java file, then test them with the simple main method provided below.

Here is the following set of classes you will implement and their inheritance relationship:

Shape

The generic abstract class shape will serve as the parent class to Circle, Rectangle and Triangle. This class MUST be abstract and it will contain abstract methods

Variables:

x – x coordinate for the shape, an integer

y – y coordinate for the shape, an integer

Methods:

getX() returns an int for the shapes x position

setX()  assign the shapes x position

getY() returns an int for the shapes y position

setY()  assign the shapes y position

A constructor with no parameters and one with x,y parameters

display()  an abstract method to display the shape

area() an abstract method to calculate the shapes area

Circle

must inherit Shape.

Variables:

radius – an int, length of the radius

Methods:

getRadius() returns an int for the circles radius

setRadius ()  assign the circles radius

A constructor with no parameters and one with x, y, radius parameters (in that order)

display() - display the circle as a text string containing the word Circle, and the x, y and radius values

area()  - calculate and return a double of the area.

Rectangle

it must inherit Shape.

Variables:

width –  an int

height – an int

Methods:

getHeight() returns an int for the rectangles height

setHeight ()  assign the rectangles height

getWidth() returns an int for the rectangles width

setWidth ()  assign the rectangles width

A constructor with no parameters and one with x, y, height, width parameters(in that order)

display() - display the rectangle as a text string containing the word Rectangle, and the x, y, width and height values

area()  - calculate and return a double of the area.

Triangle

it must inherit Shape.

Variables:

base –  an int

height – an int

Methods:

getHeight() returns an int for the Triangle height

setHeight ()  assign the Triangle height

getBase() returns an int for the Triangle base

setBase ()  assign the Triangle base

A constructor with no parameters and one with x, y, height, base parameters (in that order)

display() - display the triangle as a text string containing the word Triangle, and the x, y, width and height values

area()  - calculate and return a double of the area.

Note: all display() methods should use System.out.println()  to output a text description of the shape to the console.

If you build the classes correctly, the following main program should work:

public class Project6 {

 private Shape [] thearray = new Shape[100];  // 100 Shapes, circle's, tri's and rects

 public static void main (String [] args) {

Project5 tpo = new Project6();

tpo.run();

 }  // end of main

 public void run () {

int count = 0;

   // ------------------------   Fill the array section ----------------------

thearray[count++] = new Circle(20, 20, 40);

thearray[count++] = new Triangle(70, 70, 20, 30);

thearray[count++] = new Rectangle(150, 150, 40, 40);

// ------------------------------  array fill done ------------------------

//---------------------------  loop through the array  --------------------

for (int i = 0; i < count; i ++ ) { // loop through all objects in the array

   thearray[i].display();           // don’t care what kind of object, display it

}  // end for loop

int offset = 0;

double totalarea = 0.0;

while (thearray[offset] != null) {       // loop through all objects in the array

   totalarea = totalarea + thearray[offset].area();   // get area for this object

   offset++;

} // end while loop

System.out.println("The total area for " + offset + " Shape objects is " + totalarea);

 }  // end of run

}  // end of class Project6

When get the main program above working make sure it works with different Shape objects placed in the array. When I test the program I will provide a different ‘Fill in the array’ section of the code and expect your program to work with the new objects. This means you must implement all the methods listed in the class specifications exactly as I ask. The new code I provide will assume they are available and will call them. Remember: I will only change (and you should only change when testing) the following section of code:

     // ------------------------   Fill the array section ----------------------

thearray[count++] = new Circle(20, 20, 40);

thearray[count++] = new Triangle(70, 70, 20, 30);

thearray[count++] = new Rectangle(150, 150, 40, 40);

// ------------------------------  array fill done ------------------------