CS 204: Software Design

You may work with a partner for this assignment.

Animation with Java and inheritance

The purpose of this project is to get you warmed up on GUI programming in Java, and to start you thinking about program structures that make use of polymorphism and inheritance.

Run-time behavior

Your program will start with a class named Animation.java, which will have the main method that launches the program. You'll run your program via a command line like this:

java Animation sprites.txt 500 300

where sprites.txt contains a textual description of the various objects (sprites) that will be moving around in your animation, and 500 and 300 are examples of the animation window width and height, in pixels.

When you run this program, some sort of animation will take place. Spaceships in space, butterflies in a meadow, cars in a city, zombies in the park, or whatever strikes your fancy. The keys to this program will be the use of Java and adherence to the structure described in the next section, so the particulars of your animation don't matter a great deal.

I have provided a simple bouncing ball example in Animation.java, AnimationPanel.java, and Ball.java. I have also created a short sample FileScanner.java showing how to read a text file one line at a time and parse each line for structured information. Feel free to borrow any of this code for your program.

Program structure

Your program should model itself after the Animation/AnimationPanel/Ball program. Here's what I recommend. (If you have a better architecture, go for it, but I do want to see a top-level Sprite class plus at least two subclasses of Sprite.)

• First, please read the comments in Animation.java, AnimationPanel.java, and Ball.java to familiarize yourself with the strategy I have used in this program.

• Modify AnimationPanel.java to store an ArrayList of Sprite objects instead of a single Ball object. This modification should include a method with signature "public void addSprite(Sprite sprite)" to enable you to add Sprites one at a time to the AnimationPanel object.

• To begin the replacement of the Ball class, create a Sprite class like this (see Sprite.java):

  import java.awt.*; public class Sprite { private int positionX; private int positionY; private int velocityX; private int velocityY; // You could put width and height instance variables // here if you thought the generic Sprite should have them. public Sprite(int x, int y, int vx, int vy) { positionX = x; positionY = y; velocityX = vx; velocityY = vy; } public void step() { // Move the Sprite one step in the direction and magnitude // of its velocity. Subclasses may want to supplement this // behavior (or not) by calling super.step() followed by // any desired additional stepping actions. } public void draw(Graphics g) { // This will just be a stub, to be overridden in the // child classes. (Or you could draw a default Sprite // if you wanted to. I could see it for testing purposes-- // maybe a black rectangle or something.) } /* ... other methods you think the parent should have ... */ /* ... accessors ... */ }

• Modify the main method in Animation.java to look something like this:

  Instantiate and initialize an AnimationPanel object. Instantiate an AnimationFrame and pack the AnimationPanel into it. Open the sprites file specified on the command line. For each line in the sprites file, instantiate an object of a suitable Sprite subclass and call the AnimationPanel's add method to add it to the panel. // Begin animation do forever sleep for some time call the AnimationPanel's step method
• Create a collection of at least three subclasses of Sprite, representing the various kinds of objects you want to include in your animation. These classes will contain overrides of the methods in Sprite to arrange for the drawing and stepping.

Sprite file format

The sprite file will consist of lines of text, one per sprite, of this format:

For example:

would, presumably, cause the instantiation of an object of type Goat with initial position (200, 100) and initial velocity (10, 0) and initial color purple.

You are free to add features to your particular sprite types, making corresponding additions to the "other info" section of the sprite description line in the sprites file.