Project 2

Logistics

  • Due: Friday, September 30th AoE.
  • Submission instructions: upload seven Java files (Circle.java, EquilateralTriangle.java, Rectangle.java, RegularPolygon.java, Shape.java, ShapeDemo.java, and Square.java) to the D2L dropbox for Project 2. The preferred method is to put them all into one folder, zip that, and upload the zipped file. Ask if you need help with this.
  • You may do this project with a partner. If you do this, one partner should turn in the seven Java files on D2L and the other should just submit a comment on D2L saying who their partner is. The TA for the partner who turned it in will enter the same grade for both partners. If you choose this option, you should do the project together, not just have one partner do all the work.

Assignment

In this project, you will continue working with the code you wrote for Lab 4. You will need the RegularPolygon interface and the Square and EquilateralTriangle classes. You will also write an abstract Shape class and two new concrete classes, Circle and Rectangle. You will also write your own ShapeDemo.java to demonstrate polymorphism using your classes.

Add an abstract Shape class

Create an abstract Shape class with the following fields and methoods:

  • field color (type String)
  • methods: setColor(), getColor(), and abstract methods area(), perimeter(), and toString(). (What parameters and return types should these methods have? Ask if you are unsure.)

Bring in RegularPolygon, EquilateralTriangle and Square from lab 4.

Edit EquilateralTriangle and Square to extend Shape as well as implement RegularPolygon (as they already should). For example, the EquilateralTriangle class header should be:


public class EquilateralTriangle extends Shape implements RegularPolygon  {...}

Note: later in the project description, we will change which class Square extends. But first you can implement it to extend Shape.

Add Circle and Rectangle

Create and add the classes Circle and Rectangle to the package as well, which extend the Shape class. These two will not have an interface to implement like the Square and EquilateralTriangle, but they will still need to have constructors so that we can create objects of their types. The shape subclasses should each have three constructors:

  • Circle(radius)
  • Circle(color)

  • Circle(radius, color)

  • Square(side)
  • Square(color)

  • Square(side, color)

  • EquilateralTriangle(side)
  • EquilateralTriangle(color)

  • EquilateralTriangle(side, color)

  • Rectangle(width, height)
  • Rectangle(color)
  • Rectangle(width, height, color)

If unspecified, the color should be white, and size (radius, side, width, height) should be 1.

Change Square to extend Rectangle instead of Shape

If you think about it, it makes more sense for Square to be implemented as a subclass of Rectangle instead of a subclass of Shape. Change your code to reflect this.

Demonstrate your implementation and understanding of polymorphism in ShapeDemo.java

Notice that we can use the same syntax on different shapes because we have a sensible system of inheritance and abstraction.

Showcase your program by testing shapes of different types. You have a shape that can take many forms (Circle, Square, etc.). In the file ShapeDemo.java, create some shapes, and call the methods to get their colors, areas, and perimeters. Create a shape and assign it a square. Create a circle and assign it a circle. Can you create a rectangle and assign it a square? Why or why not? Can you create a square and assign it a rectangle? Why or why not? Think about the “is a” relationship. Comment your demo with explanations of what is happening in these experiments. If some assignments doesn’t work, comment them out and explain why in comments preceding them. Example:

// Circle myCircle = new Rectangle(2, 3); // Fail: not true that a rectangle "is a" circle.
Shape myRectangle = new Rectangle(3.5, 4, "periwinkle");
System.out.println(myRectangle);
Circle myCircle = new Circle(1);
System.out.println(myCircle);

// do more tests! Test each of the 4 shapes in at least 3 ways (minimum 12 tests)

Grading - 100 points

Readable code and good comments

  • 15 points

Some things you can think about for writing readable code:

  • using meaningful identifiers (variable names, method names)
  • indent statement blocks
  • don’t rewrite the same code!
  • use comments to explain ambigiuous or confusing constructs
  • be thoughtful about which access modifiers you use for class members
  • come back to your code a day or two after writing it and see if the way you solved the problem could be improved, or if you need to add comments

Correct implementation

  • 10 points - Circle class extending Shape
  • 10 points - EquilateralTriangle class extending Shape and implementing RegularPolygon
  • 10 points - Rectangle class extending Shape
  • 10 points - Square class extending Rectangle and implementing RegularPolygon
  • 10 points - RegularPolygon interface
  • 10 points - abstract Shape class
  • 10 points - driver ShapeDemo class

Demo

  • 15 points - write 12 distinct tests to show that your classes are implemented properly and that you understand polymorphism. Your tests don’t need to be completely exhaustive, but should contain several shape instantiations of different varieties, and print statements showing that the area and perimeter of each shape are computed correctly. You could also show that the getters and setters for the color works, that the different constructors work, and demonstrating some instances of the “is-a” relationship between objects in the hierarchy. (And possibly some non-examples in comments.) Comment the demo for yourself and your TA. You should have at least 12 tests for 1 point each. The remaining 3 points are for nice commenting and printing along with your demonstration.

Sample output

You will probably want to print out more during your demo. But you can check your area and perimter calculations:

Square. Color = white. Side = 3.0. Area = 9.0. Perimeter = 12.0
Square. Color = green. Side = 2.5. Area = 6.25. Perimeter = 10.0
Circle. Color = blue. Radius = 2.0. Area = 12.566370614359172. Circumference = 12.566370614359172
Circle. Color = blue. Radius = 1.5. Area = 7.0685834705770345. Circumference = 9.42477796076938
Rectangle. Color = periwinkle. Width = 3.5. Height = 4.0. Area = 14.0. Perimeter = 15.0
Rectangle. Color = lime. Width = 1.0. Height = 1.0. Area = 1.0. Perimeter = 4.0
EquilateralTriangle. Color = white. Side = 1.0. Area = 0.4330127018922193. Perimeter = 3.0

Grading turnaround

This program will be graded with scores in Brightspace by Tuesday, October 4th, AoE.

Go beyond

  • Draw out the inheritance hierarchy between all of your classes.
  • Make it so that you can change the default colors and default side lengths by only changing one thing in your code.
  • Use an array to demonstrate your understanding of the “is-a” relationship between shapes in your ShapeDemo class.