CS 5 Fall 2009
Short Assignment #8
Due Monday, October 19

Your assignment is to write an applet that draws a checkerboard. The checkerboard should look like this:

Your program should define some constants (i.e., final variables) that determine the configuration of the checkerboard. You may name these constants as you wish, but the names should be descriptive of their intended purposes. The checkerboard should adhere to the following rules:

• The checkerboard should have 8 rows and 8 columns. Use a constant for how many rows and columns there should be.
• Each square should be 30 pixels high and wide. Use a constant for the size of each square.
• The upper left corner of the upper left square is at position (0,0) in the applet window. You don't need to use a constant for the upper left corner position; you can assume that it's always at (0,0).
• Squares should either be red or black, as drawn above. Use the constants Color.red and Color.black.

Note that these specifications make it unnecessary to use input and output from the console (i.e., don't use Scanner or System.out).

I'll let you work out how to organize your applet's classes and methods, but I'm happy to give you a hint about how to compute information about the squares. In what follows, let's assume that we number rows and columns from 0, so that the top left square is in row 0, column 0.

If you know the row number and column number of a square, how do you determine whether it's a red or black square?

Here's a cool way. Observe that we can determine the color from the following table:

We call whether a number is even or odd its parity. So all you have to do is determine whether the row parity and column parity are equal. And, given variables row and column, how do you determine their parity? You already know the answer: row % 2 and column % 2. And you know how to determine whether two numbers are equal.

Turn in a listing of your Java file and a screen shot of your checkerboard. It's OK if you print in black and white.

To take a screen picture on Mac OS X, while you have the graphic output on your screen, use the Grab utility if you have it. On my Mac, it's in the Utilities folder within the Applications folder. If you don't have Grab, then press Command-Shift-4. That is, simultaneously hold down the Command key (the one with the apple and/or the butterfly on it), the Shift key, and 4. You'll see a funny icon. Then drag the mouse over the portion of the screen that you want a picture of. The picture will be saved as a PDF file on your desktop.

On the PC, in the Applet Viewer window, click menu "Applet" and then choose "Print... ." A "Print" dialog box will show up. Just press "OK."

Extra Credit

You can see my version by clicking here.

You will want to use the Timer class, as I did in the PsychBoxes.java and Illusion.java programs. We'll see later this week how to use Timer objects, but in the meantime you can read about them in Section 8.8 of Lewis and Loftus.

If you submit the extra credit, submit it as a separate program from the regular version, and also submit a screen shot of your green-and-white checkerboard. Again, it's OK if you print in black and white. Note also that although you will be allowed to resubmit the regular version (assuming that you get a 1 on it and you have not used up your six resubmits), you won't be able to resubmit the extra credit.