Lab 2: Improving the Crab

Table of Contents


  • Get you ready for the week's lessons.
  • Introduce you to the following concepts:
    • keyboard control
    • random numbers
    • sound
    • comments
    • dot notation
    • static methods
    • method definitions

Academic Honesty

Read the Scholastic Honesty Policy and Quest and Lab Integrity policies of the syllabus. Here are some clarifications for this particular lab:

  • This is a solo lab that you must complete individually.
  • You may discuss the code with other students for this lab.
  • You must type all the code yourself and not copy from another student.

Lab Specifications

  1. Make sure you have completed the exercises from lesson 2.
  2. Complete the Chapter 2 exercises in CodeLab. These are review exercises and you have all the information needed to complete them. If you have questions, please contact the instructor for help.
  3. Scan the textbook chapter 3 to get an overview of the material.

    It is important to have access to the book. If you have ordered the book but have not received it yet, then you can read it at the CTC. Make sure you are using the second edition of the textbook and not the first.

  4. Complete the in-chapter exercises 3.1 through 3.24 that are listed throughout chapter 3. Exercise 3.25 is optional.

    You can download the starting files from: Book scenarios.

  5. Follow the exercise steps exactly and read the textbook as you progress through the chapter to enhance your understanding.

    For those exercises steps that have a text answer, open the Scenario Information (Scenario > Scenario Information) and type the exercise number and answer after the existing Scenario Information. For example, here are my answers to the first few exercises:

    Exercises with Text Answers
    3.1: if (Greenfoot.getRandomNumber(100) < 10)
    (more answers needed...)
  6. Add the following to the top of the Scenario Information with the "VERSION or DATE" and "AUTHORS" fields filled in:
    PURPOSE OF PROJECT: Book tutorial chapter 3
    VERSION or DATE: 1.0  (The date completed)
    AUTHORS: Your name here
  7. When completed, upload all the files in the scenario to Canvas as explained in the section of this document: Deliverables.

Lab Self-Test

Be prepared to answer questions like the following after completing this lab:

  1. What code do you write to get the following result, including the end points?
    1. A random number between 0 and 9. answer
    2. A random number between 0 and 10. answer
    3. A random number between 1 and 10. answer
    4. A random number between -10 and 10. answer
  2. To cause an actor to make a random right-turn between 0 and 45 degrees inclusive write ________.
    1. turn(random(45));
    2. turn(getRandomNumber(45));
    3. turn(Greenfoot.getRandomNumber(45));
    4. turn(Greenfoot.getRandomNumber(46));
  3. To remove an object from a scenario world, call the Actor method ________.
  4. True or false: defining a method means it will be executed.
  5. True or false: method calls always have parenthesis, even when a method does not define any parameters.
  6. True or false: defining short methods makes it easier to understand the logic of a program.
  7. To check whether a key on the keyboard has been pressed, call the Greenfoot class method ________.
  8. To play sounds, first add the sound files to the ________ folder of your scenario.
  9. To play a sound file, call the Greenfoot class method ________.

Grading Criteria

The instructor will evaluate your lab using the following criteria. Thus you should check your lab against these criteria to maximize your XP.

Lesson Exercises (from Class)

  • 2: All lesson exercises attempted and turned in
  • 1: Some lesson exercises not completed and turned in or other problems found
  • 0: No lesson exercises turned in or wrong folder name

Tutorial Lab (Textbook)

  • 4: Demonstrates mastery of the lab exercise:
    • Applies concepts from the lessons appropriately
    • Follows the steps exactly
    • Exercises perform correctly
  • 3: Has all the major functionality expected:
    • Demonstrates many techniques from the lesson
    • May deviate from the specified steps in some way
    • Implementation seems more complicated than necessary.
  • 2: Has much of the functionality expected:
    • Demonstrates some techniques from the lesson
    • Deviates from the specified steps in some way
    • Implementation seems excessively complicated.
  • 1: Serious functional problems but shows some effort and understanding:
    • Follows at least 1/2 of the of the specified steps
    • Has a major error (detected by the browser) or many minor errors
    • Demonstrates few techniques from the lesson
  • 0: Not turned in or wrong folder name

CodeLab Exercises

Number completed correctly / number exercises * 8 and rounded up to the nearest integer.

Maximum XP: 14


CodeLab is submitted automatically, but other lab work must be submitted as described below.

  1. On your computer, create a folder for the lesson exercises named "lesson" (no extra characters) and place all the exercise files from Lesson 2 into this folder. There should be only one scenario, which is the culmination of all the lesson exercises on the bugs scenario completed during class.
  2. Add the errors.txt file from Exercise 2.3 to the lesson folder as well.
  3. Create a second folder named "tutorial" (no extra characters) and place the entire tutorial scenario from chapter 3 of the textbook into this folder. There should be only one scenario. Do not include the files from previous labs.
  4. Zip both folders and submit the zip files to the Lab 2 slot of Canvas.

Please do not add any extra characters to the above folder names. Also, do not put any spaces or special characters like #, : or $ in zip file or folder names. Your crafted code must work as submitted. Remember to test and double check your files before and after submitting them. If you make a mistake, you can resubmit up to the deadline but must resubmit all your files. For information on resubmitting see How do I change an assignment in Canvas?

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Last Updated: February 12 2017 @15:18:56