Implement a drawing program in Java.

Here are some ideas for getting started: (a) study the BallWorld program in Budd.  Understand how the paint method works and what you need to do to get graphics up on the screen.  (b) think about how a vector (see Budd on Java's Vector class, page 100) could be used to store a succession of mouse positions corresponding to dots of ink or to vertices of a polyline).  (c) look and see how you can detect mousePressed and mouseReleased events by subclassing the MouseAdapter class (Budd, page 101).

Here is the minimum functionality you should support:

1. Bring up a frame that has a drawing area.  (If you wish, create an applet and you won't need a separate frame.)
2. Detect mousePressed events (or, if you prefer, mouseDragged events) and cause something to be drawn at the current mouse position whenever the mouse is pressed within the drawing area.
3. The ink marks or whatever the user is drawing should accumulate as s/he draws more and more of them.
4. If the user picks up the frame (window) and moves it or resizes in, the program should correctly repaint the screen with the current drawing.

Here's an applet that shows the minimum functionality. To start a new painting, reload the applet.  (In Netscape Navigator, you reload the applet by holding down the shift key while clicking on Reload.)

Optional functionality:

5. Provide a way for the user to erase the screen without restarting the program.
6. Provide a way for the user to erase selectively within the current drawing.
7. Provide a way for the user to change the color of what is being drawn.
8. Provide a way to change the brush size or pen size.

Programming style:  Define your classes carefully. Comment your code.  Explain (in your comments) where you are using inheritance.  Explain (in your comments) where you are providing a method that overrides the one that would be inherited.  Choose identifier names carefully.  Use appropriate indentation and other formatting.  Make your code easy to read and understand.