You will be working in Quad lab 7. Experiment with the BlueJ project we saw in lectures.

1. Login with your zPass login and password.
2. Download the ‘Turtle’ project zip file from here .
3. Unzip both files in your “My Documents” folder.
4. In the ‘Start’ menu, select ‘Programs’ and click on BlueJ.
5. Select ‘Open Project’ from the File menu and open the ‘Turtle’ project.
6. Create a new ‘MyTurtle’ object by right clicking on the MyTurtle class and selecting new MyTurtle()
7. Give your turtle a name and press OK.

Simple shapes

1. Right click on the red MyTurtle object and select the void drawSquare(int sideLength) method.
2. Enter a side length of 100 and press OK.
3. Observe what happens in the World window.
4. Try drawing squares of different sizes.
5. What direction does the turtle face before and after you call the method?
6. Double-click on the MyTurtle class to open the source-code.
7. Read the drawSquare method. Can you explain why the turtle has a different direction after the method is called?
8. What could you do to fix this so the turtle is facing the same way before and after the method?
9. Change the code so that it draws a triangle instead of a square.

Using the debugger

1. Read the method drawPolygon and try to understand how it works.
2. Run it with different parameters to see if it does what you expect.
3. In the source window, click on the line number for the line “if (numberOfSides < 3)“. A little red stop sign should appear.
4. Run the method again with numberOfSides set to 6 and sideLength set to 100. The Debugger window should appear.
5. Press the Step button and watch how the program steps through the code.
6. Run the method again with numberOfSides set to 2. Can you predict what will happen?

Spirals

1. Read the method drawSpiral and try to understand how it works.
2. Try drawing a spiral with length = 10 on a piece of paper following these instructions.
3. Use the debugger to step through the method. Does it do what you expected?
4. Change the line ‘length = length – 2‘ to ‘length = length – 4‘. How will this change the spiral? Run it and see.
5. Change the line to ‘length = length + 4‘. What happens now? Why?
6. Change the line ‘rotate(90)‘ to ‘rotate(88)‘ and see what happens.
7. Can you make other pretty patterns by making a few simple changes?