LAB 8 - Introduction to Programming (part 3 - turtles)

Lab Exercises

Topics

n To create a method to reuse a series of Java statements

n To be able to use methods to perform tasks

n To be able communicate with methods

Exercises

3.5 Creating Methods

Type in the following program shell:

/* Program that displays different figures using turtle graphics

 * World and Turtle classes are defined in bookClasses developed

 * at Georgia Tech by Mark Guzdial / Barbara Ericson

 *

 * @author Wayne Summers

 * @date   Sept. 4, 2007

 */

public class TryTurtles

{

  public static void main(String[] args)

  {

    World newWorld;

    Turtle myTurtle;

    newWorld = new World();

    myTurtle = new Turtle (newWorld);  

  }

}

Compile and run the program.

3.5.1 Methods that Take Input

Type in the following method between the bottom two braces:

static void drawSquare(Turtle turtle1)

  {

    turtle1.turnRight();

    turtle1.forward(30);

    turtle1.turnRight();

    turtle1.forward(30);

    turtle1.turnRight();

    turtle1.forward(30);

    turtle1.turnRight();

    turtle1.forward(30);

  }

Compile and run the program.

Type the following statement in the main method below the creation of myTurtle.

    drawSquare(myTurtle);

Change the drawSquare method to look like:

  static void drawSquare(Turtle turtle1, int width)

  {

    turtle1.turnRight();

    turtle1.forward(width);

    turtle1.turnRight();

    turtle1.forward(width);

    turtle1.turnRight();

    turtle1.forward(width);

    turtle1.turnRight();

    turtle1.forward(width);

  }

and change the call to   

            drawSquare(myTurtle, 30);

QUESTIONS:

1. Modify your program to draw four squares of different sizes and colors in four different locations of the world. [Don’t forget to pick up the pen before you move the turtle and to hide the turtle when you are finished]

Submit the answers through the DropBox in WebCT.