Computer Science I - 810:061:01 and 810:061:02 - Fall 2002 - 2nd four weeks

ObjectDraw blue sheet quick reference.

VIP: First four weeks web page outline/lecture notes/example applets and java resources. Please review these often until October 31st gets here!

HELP: Color coded TA Schedule for Daniel and PJ, indicating the WRT 339 lab TA hours in BLUE and the WRT 112 TA hours in RED.

  1. Monday, September 23rd Defining Your Own Classes, such at T-Shirts (see Williams College book, chapter 4) and coin purses (See page 90-92 of Big Java).

  2. Wednesday, September 25th Local variables, PIVs (Private Instance Variables) and Parameters are the big three categories of data you will see inside of any class definition.

  3. Here is the Coin Purse example from Wednesday's class 9/25/02.

  4. Here is the Coin Purse Version 2 to preview befor Friday's class on 9/27/02. This is the last Friday class in September, by the way. Where will your understanding of Java and programming and problem solving and skill at developing algorithms be by the end of the last full week of October classes?

    Play with this Coin Purse program BEFORE Friday, September 27th, 2002.

  5. How do I use the Project menu, Compiler Settings for Project... command? If you don't want to save a Project that uses objectdraw.jar under a NEW NAME, using Project menu, Save As... to ensure all the settings are correct.

    • Command you use when in jGrasp.

    • See dialog box for Flags/Args/Main and the need to set the following (for Java, NOT for Ada!):
      For ALL programs that use the William's College 
          ---                                 textbook objectdraw package.
                -classpath objectdraw.jar
      For my Java program that uses the Purse class, you just add
              that to the -classpath so the compiler looks for it.
                -classpath objectdraw.jar
      Note that the file should be in the same folder or
            subdirectory as you have the client .java that imports
            the class and uses its capabilities by constructing
            Purses or Tshirts or whatever objects of the class!

    • See dialog box for HTML settings for the Applet Window that the Project should have.
                                    is all you have to add to the
                                    default HTML, which you can Copy
                                    to the windows clipboard with
                                    control+C and then Paste back
                                    with control+V.
              archive="objectdraw.jar"      <---- Only phrase you add.
              code = %MAIN_CLASS.class
               width = 400
              height = 400>
      Note:  2 Greater Than and 1 Less Than symbols removed so you
             can see the HTML, instead of the browser's 
             interpreting of the HTML!  See the GIF file snapshot...

    • See a very instructive sample output that illustrates why pennies and storing your money at int (or long) inside the class is SO MUCH BETTER than storing it as double (or float). For example: $7.89 should be stored as the int 789 for the number of cents or pennies it represents, rather than the 7.89 floating point or REAL number representation the computer provides. CoinPurseFlagsArgs.gif CoinPurseSettingsHTML.gif CoinPurseProjectMenuCompilerSettingsCommand.gif CoinPurseStorePennies.gif

  6. Assignment #4: Lab 4: Yahtzee game - dice and writing the Die class.

  7. How to do WHILE LOOPS and REPETITION in Java using the while statement.

  8. While loops exercise and examples. Monday, 09/30 class exercise. Do the exercise on your own AGAIN before the Wednesday class. Can you think of several different ways to solve it?

  9. Answer to Die class getRoll() method questions. The PIV currentRoll is an intEGER variable that remembers what the value of the die is, for each of the objects in Yahtzee game. die1, die2, die3, die4 and die5 each have their own PIVs.

  10. Clarification on the canvas and the this Java keyword used to refer to the methods or the PIVs of the current object.

    this.canvas = canvas;

  11. You do NOT need to use the this.canvas = canvas idea, unless you wanted to have your roll() method create a new RED LINE for every roll that the user did. Then it would need to know where, from the PIV canvas! There are 14 RED lines drawn on the Yahtzee game shown below, representing the 14 times that the user clicked the Reroll button.

       // From the Die class, with the lines to implement the roll
       // removed, but with the two statements that draw a RED LINE
       // and prepare for the position of the next RED LINE shown.
       // Note how this would NOT work, except for the PIV canvas!
       //                                                  ------
       public void roll()
          //                               ------
          new Line(150, lineY, 250, lineY, canvas).setColor( );
          //                               ------
  12. Friday, October 4th Lecture notes and BoxBall Lab 5 assignment. CHAPTER 5: Read and study carefully chapter 5 of the Williams College textbook as you study these lecture notes.

  13. Lab #5 assignment to play the simple game of dropping a ball into a box from a certain height. Note that you must do a DESIGN OF YOUR CLASSES FIRST!

    Boxball assignment: THERE ARE HANDOUTS FOR LAB #5 TAPED TO MY OFFICE DOOR, Wright 106. (The 9 a.m. class did not get the handout).

  14. Download the lab_5.gpj that has RELATIVE file references. You would need to fix the other lab_5.gpj project file, as it was accidently saved with absolute file references to,, and objectdraw.jar files.

  15. See the Boxball game phase #1 demonstration, with helpful hints and directions for getting more than halfway through the project.

  16. See the completed Boxball game, with a few extra features added.

  17. Class #18 review: Summary of and examples from the Monday, October 7th class and lecture.

  18. Boxball game Helpful Hints email #1 of 2.

  19. Boxball game Helpful Hints email #2 of 2. Also EXAM ONE being Wednesday, October 16th.

  20. Class #19 preview: Raindrops keep filling up the collector and falling on my head.

    Example helpful for understanding the public onBallHittingBottom() method techniques and issues for your Boxball class, and how the Ball class could call it. Hopefully, this will be clear after you study THIS example. Look at this ahead of time. Review of class #18 and chapter 5 is useful too, as this is a development of the DropCollector and the FallingBall classes from pages 156-157 of the book.

  21. Here is an example that uses a dialog box to gather input from the user, then uses standard String processing and while loop techniques to print your favorite movie in a triangular pattern, using the Courier New font.

  22. See a Boxball game that does not produce correct output. "Hey, I Made that Shot!" Boxball game, with some added features like randomly sized ball objects, and the 10 second pause() before doing the hide() method action.

  23. Boxball game: Lab 5 at 5 p.m. is okay. Lab 5 by 9 a.m. or 10 a.m. isn't required. Also important information about midterm EXAM.

  24. EXAM WEDNESDAY: while loop and Color and FilledRect practice question and exercise. To be solved in Monday exam review, but try to solve it yourself FIRST, at least the simpler version. Can you solve this without looking at the book or lecture notes or blue sheet? Try to simulate the closed book test conditions and test your memory and understanding of the while loop pattern.

  25. Midterm exam outline of topics and practice questions is still in progress.

  26. Solution to while loop RED rectangles problem: while loop exercise has 5 staggered red rectangles.