Lab 3: Shapes Scene Graph
CS 241: Data Structures, Spring 2007

Goals for this assignment are to:

• interfaces
• abstract classes
• inheritance

Reading

Carefully read all of Chapter 3 before starting this assignment.

Directions

1. Begin with the Shapes program (zip file) discussed in class. The UML diagram for it can be seen here (pdf).

2. Run the code first without making any changes. You should see a scene with 2 houses and some grass.

   
3. Open the ShapesFrame class and go to the method makePicture(). Change the code to obtain a different picture. You have Boxes and Polygons to work with.

4. Carefully look through the code to understand it's structure and then make the following additions:

   • Add an Oval class. Since it will look a lot like the Box class, you may chooseto extend the Box class to create the Oval shape, or not. Test your code.

   • Extend the PolyShape class to create a FilledPolyShape. Note, to fill a Polygon object you need to use the command g.fill(p) instead of g.draw(p) in the drawShape method. Test your code.

   • Add a scale method to the Shape interface. You will then need to make sure that a scale method is available to all of the shapes. Think about how scaling is done before beginning this. Scaling is always relative to a fixed point - where do you want this fixed point to be? What will happen to the composite shape when all of its components are scaled? Will they stay in the correct relative positions?

   • Create a single interesting picture that tests your code on the Oval class, the FilledPolyShape, and the scaling capabilty for all the different types of Shape objects. Include a Shape object that contains some structure (i.e. has several Composite nodes).

     Example: the big picture is scaled into a little picture.

5. The code already has some javadoc comments included. Add javadoc comments where they are missing.

Evaluation

By no later than class on Mon September 24, you should do the following:

1. Added the Oval and FilledPolyShape.
2. Added scaling to all of the shapes.
3. Created a picture illustrating all of the above.
4. Included the javadoc and jar file.
5. Zip together the entire project and emailed the code as an attachment to gorr@willamette.edu. Include CS241 Lab 3 in the subject line.

By Thursday (Sept 27) you should demonstrate the code to the instructor.

We will look at your pictures in class.