CS111, CS Dept, Wellesley College Lab 3 Wednesday, September 17, 2007

Total checkmarks:

Go to the download directory on puma and download the lab3_programs directory to your desktop.

EXERCISE 1 - Another Java Execution Model Diagram

public class ScooterWorld extends BuggleWorld {

  public void run () {
    ScooterBuggle sam = new ScooterBuggle();
    ScooterBuggle sara = new ScooterBuggle();
    Color c = Color.blue;
    sara.setColor(c);
    sam.scootLeft(4);
    sara.forward(4);
    sam.switchPositions(sara);
    sara.forward(8);
    sam.left();
    sam.forward(8);
    sam.setColor(c);
    sam.scootRight(4);
    sara.setColor(Color.red);
    sara.left();
    sara.forward(4);
  }

}


class ScooterBuggle extends Buggle {

  public void scootLeft (int steps) {
    this.left();
    this.forward(steps);
    this.right();
  }

  public void scootRight (int n) {
    right();
    forward(n);
    left();
  }

  public void switchPositions (Buggle b) {
    Location p = b.getPosition();
    b.setPosition(this.getPosition());
    this.setPosition(p);
  }

}

EXERCISE 2 - Bagel Rugs

Hints

• It is helpful to realize that the rug design consists of three concentric rings of 3x3 grids, as indicated by the heavy black outines shown below (the lighter black lines demarcate the 3x3 grid patterns):

• Here are some helpful patterns to break the rug:
  Patterns 1 and 2 appear in the outter ring, while patterns 3 and 4 appear in the inner and center rings respectively. However, feel free to come up with your own, especially instead of pattern 1 and pattern 2 above.

  Starting code for this excercise can be found in LabRugWorld.java file, within the lab_programs folder you downloaded.

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  EXERCISE 3 - Checkerboards

  Task
  Today in lab you are going to write a program to draw checkerboards. You have already done so in the previous lab, but in a smaller scale.

  We can draw the checker board in many different ways, following different drawing strategies. A couple of those strategies are shown below.

  Checker Board Strategies

  • Square Checker Board
    In this approach, we draw the checkerboard by drawing 2 x 2 pieces, one at a time. Here is such a piece, in black and red, as an example:
    

  • L Checker Board
    This time we draw the checkerboards by finishing L-shaped pieces one at a time. As an example, here is such a piece in black and red:
    

• Spiral Checker Board
  If you were curious, here is one more approach, to draw the checkerboards:
  
  

  Can you think of any others?

Implementation of Checker Board Strategies

• Square Checker Board
  

  • You can find starting code for this approach, in the file CheckerBoardSquare.java
  • Start your coding, by writing a method to produce the basic square. Name it draw2x2Square()
  • Invoke this method to test it. Can you produce different color basic squares? Do you need to make any changes to the code in the method draw2x2Square() in order to do so? You shouldn't!! Only the way the method is invoked should change!
  • Add a method, named draw4x4Square() , to draw a 4 x 4 square. This method will use the previously defined and tested draw2x2Square() method.
  • Test this newly defined method (draw4x4Square() )
  • Continue this way.

• L Checker Board
  You can find starting code for the L Checker Board approach, in the file CheckerBoardL.java