CSCI 161b: Introduction to Computer Science • Fall 2012 • University of Puget Sound

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CSCI Homework Assignment 2 - The Robot

Due Wed Sep 12 at beginning of class

Introduction

For this assignment, you will be creating another simple Robot class in Java. This is a very primitive Robot. The Robot has only a few capabilities: it can be turned on and off, it can move forward, it can turn to the right, it can draw itself on the screen, and it can print out information about itself. A complete specification of the Robot class can be found at the bottom of the page.

Note that these Robots are seen from the top down!

The Assignment

You'll be making this Robot from scratch. But don't panic: I'll walk you through some of steps. Jut remember to take it slowly, one step at a time. Test your code frequently, after each step. It will make errors easier to find.

Ask many questions; I'm happy to help you out!

1. Start by downloading a copy of Homework2.zip. This project includes the Circle, Square, and Triangle objects you're familiar with, so that you can use them to make your robot. Your robot will be made of Shapes! Note that this is not the same project as previously (I've modified it slightly to make it easier to use). Do not make any changes to the Circle, Square, or Triangle classes! Only to your Robot class!
2. First, make a new Robot class by clicking the "New Class" button. There, now you're started! You can double-click this class to see its source code. You can also make new Robots by using the BlueJ interface.
3. Your robot will need to maintain some information about its state by using fields--for example, the robot may want to remember a name (e.g., "Robbie", "R2D2"). Make sure you give the field a meaningful name so the rest of your code is easier to read.
4. Now modify the constructor so that it takes a single parameter: the robot's name. This parameter should be a string. Remember, this parameter will need to be stored in the object's state field!
5. Add a toString() method so that we can print out the Robot's status. Remember, this method should return a String representation of the robot--for example "Robbie the Robot."
6. Remember to test each method as you create it using either the Code Pad or the BlueJ Interactive Window.
7. Now it's probably a good idea to define what your robot looks like, using the the Circle, Square, and Triangle objects. For example, we might give it a body that is a Square, and a head that is a Circle. Since we don't want our robot to lose its head, we'll want to make these body parts into fields. You are free to make your robot as awesome looking as you want, but more complicated robots may be more difficult to move and turn later. I suggest starting with just a body and a head. Also, make sure you have time to finish the rest of the assignment!
   Hint: You can make a new Circle, Square or Triangle in your robot by using the new keyword. For example, I might make the body of my robot a Square by using body = new Square(); in the constructor (be sure to have declared the body variable with the other attributes/fields!)
8. Once you've defined what your Robot will look like, let's give the robot a method to draw itself on the screen. Since the Shape objects that make up our robot are shown on the screen using a method called makeVisible(), let's also give our Robot a makeVisible() method. This method should tell all of the body parts to make themselves visible. Test that calling this method does draw your robot on the screen (and that your robot looks the way you want it to!)
9. The next thing we'll want to do is make sure our robot can be turned on. The Robot object will need to keep track in the state of whether it is on or off. And we'll want to make methods that turn the robot on and off (see the documentation below for those methods' signatures). Remember to test that these methods work (and do change the robot's state), and that nothing else broke. You also will want to change the toString() method so that the robot's state is included when it prints out the status.
10. Now that we can turn our robot on, we can go ahead and create a method to move the robot forward by a certain distance (again, see the documentation for the method signatures). We can move the robot by moving its component parts--e.g., moving the body, the head, etc. Remember that we should only move the robot if the robot is turned on! Test to make sure this works.
11. Next, let's write the method that will turn the robot 90degrees to the right. Again, this should move the component body parts. You may need to be careful about your robot design so that it still looks okay when turned around! (Consider what functionality is missing from the Shape objects that would help us out). Test that it works correctly no matter how many right turns you make.
12. So it seems like we're done, right? We've included a RobotTester class to help test your completed Robot. Does everything seem to work? Feel free to add more tests to the class if you're not sure.
13. It's possible that your moveForward() method doesn't work when the robot is turned--because forward is no longer "up" on the screen. This means your robot is going to need to keep track of what direction it is facing. Add this capability to your robot if you haven't already. Once you've done that, you'll need to modify the moveForward() method to consider what direction the robot is facing when determining how to change the component Shapes. Hint: One simple way to do this is to use a variable to the state that keeps track of current direction, and then use a conditional statement to choose which direction to move when moveForward() is called.
14. Make sure to test everything thoroughly. Once you're sure it works, You can use the RobotChaos class to view many copies of your robot moving randomly! Weee!!
15. Finally, make sure to include comments in your code explaining what you did!

Submitting

Submit your solution through BlueJ following the same submission directions as presented in Lab A. However make sure to select "Hwk2" instead of "LabA".

Submitter will accept the Robot.java file.

Grading

This assignment will be graded on the following criteria:

• The Robot object can be turned on and reports its state using toString()
• The Robot is able to move forward and turn to the right. The Robot visually appears to turn.
• The Robot only moves if it is on!
• The moveForward() method moves the Robot in the direction that it is facing.
• Your code is documented with comments explaining what you've done.

Class Documentation

java.lang.Object
  Robot

          public Robot(java.lang.String _name)

          public void makeVisible()

          public void moveForward(int distance)

          public java.lang.String toString()

          public void turnOff()

          public void turnOn()

          public void turnRight()

Joel Ross • jross@pugetsound.edu

Assignment adapted from Chuck Hommel

Page Last Modified: 2012-09-10 13:01:23 -0700

Mathematics and Computer Science Department • University of Puget Sound