EECS1030 Lab 04

Introduction

The purpose of this lab is to implement a class that uses aggregation and composition. This lab also introduces the concept of recursion and uses your implemented class in a recursive method to draw a version of the Koch snowflake.

Question 1: Implement a turtle class

Turtle graphics is a method for drawing geometric primitives (such as points, lines, and curves) in the Cartesian (xy) plane. Logo was one of the early computer languages designed for educational purposes, and it had turtle graphics as one of its main features.

In turtle graphics, the client has control of a cursor (the turtle) that responds to commands such as "move forward 1.5 units", "turn right", "turn left", and "turn 45 degrees". As the turtle moves, it leaves behind a trail using a pen; the pen can have attributes such as colour and radius to control the trail colour and thickness.

The turtle needs attributes to represent its position in the plane, the direction that it is facing, and the pen color. The position can be represented using a Point2D object, and the direction can be represented as an angle greater than -360.0 and less than 360.0 degrees (measured counterclockwise from the positive x axis). The pen color is represented using a java.awt.Color object. Your class should use composition to manage the Point2D object and aggregation to manage the java.awt.Color object.

Furthermore, our turtle will have a class invariant: The position of the turtle is always inside or on the circle having radius equal to 1. If the turtle is asked to move outside of the circle, then the turtle will move as far as possible in its current direction and then stop at the perimeter of the circle.

Implement a Turtle class that supports turtle graphics. Use the code shown below to start your program. The code below uses the StdDraw class from the textbook Introduction to Programming in Java: An Interdisciplinary Approach by Robert Sedgewick and Kevin Wayne. StdDraw provides the capability to easily create simple drawings in a Java program. In this lab, StdDraw uses an Cartesian coordinate system with the bottom left corner of the window having coordinates (-1.0, -1.0) and the top right corner of the window having coordinates (1.0, 1.0).

Below you will find several resources to help you with your implementation:

• starter code for Turtle. Make sure that you do not modify any of the starter code given to you, as this make break the tester. The starter code includes the following features:
  • all of the private fields that are required
  • a default constructor
  • toString
  • a main method that may help you test your implementation
• API for Turtle, Point2D, IVector2D, TurtleUtil, and StdDraw
• jar file for Point2D, IVector2D, TurtleUtil, and StdDraw
• a simple JUnit tester
• web page for the test program

It is recommended that you complete Turtle in the following order:

1. Turtle(Point2D position, double angle, Color c)
2. Turtle(Turtle other)
3. getAngle()
4. getPenColor()
5. getPosition() (remember to use composition)
6. setPenColor(Color c) (remember to change the turtle's pen color and the pen color of StdDraw)
7. turn(double delta)
8. turnLeft()
9. turnRight()
10. maxDistance() (see note below)
11. move(double distance) (see note below)

Note that you have three ways to test your code: the JUnit tester, the Koch snowflake client program, and the main method of Turtle.

maxDistance and move

Computing the maximum distance that the turtle can move before it hits its enclosing circle requires some math:

If you examine the API of TurtleUtil you will find a method that helps you with Step 2.

For the move method, you may find the methods Vector2D.dirAndMag and Turtle.maxDistance to be useful in your implementation.

In the move method, you need to draw a line using the turtle's pen color. To draw a line from a point (x1, y1) to a point (x2, y2) using the turtle's current pen color, use the following code:

StdDraw.setPenColor(this.penColor);
StdDraw.line(x1, y1, x2, y2);

Submit

Submit your solution before Tuesday February 10, 4pm. To submit, log into a computer of the Prism lab (clips showing how to log in from home and transfer files can be found here). Transfer your Turtle.java to your EECS account (if it is not already there). Create a file named group.txt in the directory which contains the lab directory which contains the turtle directory which in turn contains Turtle.java. Do not put the group.txt in the same directory as Turtle.java. Each line of the file group.txt contains the EECS login name of a member of the group. Open a terminal and go to the directory that contains the file group.txt. In that directory, run the following command.

submit 1030 lab4 group.txt lab/turtle/Turtle.java

If something fails, you will be see something like

submitted:  group.txt (18 bytes)
submitted:  Turtle.java (4871 bytes)
All files successfully submitted.

Your Turtle class compiled successfully.
Your Turtle class passed all the tests.
Your code contains no style errors.
frank in group.txt is not a valid EECS account
SUMITTED FILES HAVE BEEN REMOVED.
PLEASE SUBMIT AGAIN.

Fix your code and submit again. If you successfully submitted your code, you will see something like this

submitted:  group.txt (19 bytes)
submitted:  Turtle.java (4871 bytes)
All files successfully submitted.

Your Turtle class compiled successfully.
Your Turtle class passed all the tests.
Your code contains no style errors.
Your group.txt file has been successfully validated.