LAB 7 - Introduction to Programming (part 2 - turtles)

Lab Exercises

Topics

n To introduce computation as simulation

n To introduce the turtle and talk about the history of using turtles to teach programming

n To show how to add classes to the classpath in DrJava

n To create objects in Java

Exercises

3.4 Working with Turtles

3.4.1 Defining Classes

Make sure the classpath is set to include the classes from the book:

3.4.2 Creating Objects

Create a world named myWorld:

> World myWorld;

> myWorld = new World();

>System.out.println(myWorld); //calls toString method for the myWorld object

[Find World in the API for the Book Classes]

Create a turtle named myTurtle on myWorld

>Turtle myTurtle;

> myTurtle = new Turtle (myWorld);

> System.out.println(myTurtle);

[Find Turtle (and SimpleTurtle) in the API for the Book Classes]

Create a second turtle named yourTurtle on myWorld at x=40, y=50

>Turtle yourTurtle;

> yourTurtle = new Turtle (40, 50, myWorld);

> System.out.println(yourTurtle);

3.4.3 Sending Messages to Objects

            Use forward(), forward(x), backward, backward(x), turnLeft(), turnRight(), and turn(x) to move the two turtles around the world where x can be positive or negative integers

3.4.4 Objects Control Their State

            Try making one of the turtles to leave the world (use a large value for x)

            Where is the turtle (“print” the turtle to find out)

3.4.5 Additional Turtle Capabilities

Explore other SimpleTurtle methods (hide, show, penUp, penDown, moveTo) to draw squares, the letter T, and other objects

QUESTIONS:

Submit the answers through the DropBox in WebCT.