Questions about a MasterQuize program

Question

Hi, everyone.
I got a in-class case study program like this in the class:
* This class stores/represents a question that has one of two
* answers: True or False.
* <p></p>
* It needs to track the following information:
* <ul>
* <li>Question text</li>
* <li>Correct answer</li>
* <li>The user's answer to the question</li>
* <li>Points value</li>
* <li>Category</li>
* <li>Difficulty rating</li>
* </ul>
// Our question should allow us to do the following:
// - Create question (constructor) -- may be overloaded
// - Print (display) question
// - Check client's answer for correctness
// - Get points value for question (0 or max)
//   - Add "No-BS" grading option
// - Getting client's answer
// - Check to see if answered by client
public class TrueFalseQuestion
    // Class constants (to simplify changes to common values)
    public static final int MIN_DIFFICULTY_LEVEL = 1;
    public static final int MAX_DIFFICULTY_LEVEL = 5;
    public static final int DEFAULT_DIFFICULTY_LEVEL = 1;
    public static final int DEFAULT_POINT_VALUE = 1;
    public static final String DEFAULT_CATEGORY_VALUE = "none";
    // Class instance variables
    private String questionText;
    private String correctAnswer;
    private String userAnswer;
    private int pointsValue;
    private String category;
    private int difficultyLevel; // TODO: Set a range for difficulty levels
     * @param text The literal wording of this question
     * @param answer The correct answer for this question
     * @param pts The total points available for this question
     * @param ctgry Category keyword for this question
     * @param level The perceived/intended difficulty level of this question
     * <p></p>
     * Defines a TrueFalseQuestion object.
    public TrueFalseQuestion (String text, String answer, int pts, String ctgry, int level)
        // Set starting values for all instance variables
        questionText = text.trim();
        correctAnswer = answer.trim();
        userAnswer = null; // No user answer supplied yet
        if (pts >= 1) // We assume that every problem is worth at least 1 point
            pointsValue = pts;
        else
            pointsValue = DEFAULT_POINT_VALUE;
        category = ctgry.trim();
        if (level >= MIN_DIFFICULTY_LEVEL && level <= MAX_DIFFICULTY_LEVEL) // within range
            difficultyLevel = level;
        else
            difficultyLevel = DEFAULT_DIFFICULTY_LEVEL;
    // Simplified (overloaded) constructors
     * @param text The literal wording of this question
     * @param answer The correct answer for this question
     * @param pts The total points available for this question
     * <p></p>
     * Defines a TrueFalseQuestion with default values for category and difficulty level.
    public TrueFalseQuestion (String text, String answer, int pts)
        // Call pre-existing constructor with default category and difficulty
        this(text, answer, pts, DEFAULT_CATEGORY_VALUE, DEFAULT_DIFFICULTY_LEVEL);
     * @param text The literal wording of this question
     * @param answer The correct answer for this question
     * <p></p>
     * Defines a TrueFalseQuestion with the default point value, default category,
     * and default difficulty level.
    public TrueFalseQuestion (String text, String answer)
        // Call pre-existing constructor with default points, category and difficulty
        this(text, answer, DEFAULT_POINT_VALUE, DEFAULT_CATEGORY_VALUE,
             DEFAULT_DIFFICULTY_LEVEL);
     * @param text The literal wording of this question
     * @param answer The correct answer for this question
     * @param pts The total points available for this question
     * @param ctgry Category keyword for this question
     * <p></p>
     * Defines a TrueFalseQuestion with the default difficulty level.
    public TrueFalseQuestion (String text, String answer, int pts, String ctgry)
        // Call pre-existing constructor with default points, category and difficulty
        this(text, answer, pts, ctgry,
             DEFAULT_DIFFICULTY_LEVEL);
     * @param text The literal wording of this question
     * @param answer The correct answer for this question
     * @param ctgry Category keyword for this question
     * <p></p>
     * Defines a TrueFalseQuestion with the default point value and the default
     * difficulty level.
    public TrueFalseQuestion (String text, String answer, String ctgry)
        // Use default points and difficulty
        this(text, answer, DEFAULT_POINT_VALUE, ctgry, DEFAULT_DIFFICULTY_LEVEL);
     * @param text The literal wording of this question
     * @param answer The correct answer for this question
     * @param pts The total points available for this question
     * @param level The perceived/intended difficulty level of this question
     * <p></p>
     * Defines a TrueFalseQuestion with the default value for the question category.
    public TrueFalseQuestion (String text, String answer, int pts, int level)
        // Use default category
        this(text, answer, pts, DEFAULT_CATEGORY_VALUE, level);
    // Clients can invoke this method to retrieve the text of the current question.
    // We chose to return the text instead of printing it; this allows the client
    // to decide how it should be presented (via a GUI, over a network, etc.)
    public String getQuestion ()
        return questionText;
    // This method allows the client to store the user's answer inside the
    // TrueFalseQuestion object for easy comparison
    public void submitAnswer (String ans)
        userAnswer = ans;
    // This method reports whether the submitted answer matches the correct answer
    public boolean answerIsCorrect(String userAns) // This version does all the work
        if (userAns == null) // No response from user (yet)
            return false;
        else
            // Normalize and compare answers
            char key = normalize(correctAnswer); // Get 't' or 'f'
            char ans = normalize(userAns); // Get 't' or 'f'
            return (key == ans);
    public boolean answerIsCorrect ()
        return answerIsCorrect(userAnswer); // Call previously-defined version
    public int getPointsValue()
        return pointsValue;
    // Return the points awarded for the user's answer. This method does
    // NOT support partial credit; answers are either correct or incorrect.
    // If the "No-BS" option is selected, blank (unanswered) questions receive
    // 1 point automatically; otherwise, the score will be either 0 or the
    // question's normal points value.
    public int getPointsEarned(boolean useNoBSRule)
System.out.println("useNoBS: " + useNoBSRule + "\tuserAnswer: " + userAnswer + "\tcorrectAnswer: " + correctAnswer);
        if (useNoBSRule && (userAnswer == null))
            return 1;
        else if (userAnswer == null)
            return 0; // Without "No-BS", treat blank problems as incorrect
        if (answerIsCorrect() == false)
            return 0;
        else
            return pointsValue;
    // This method returns true if the user has submitted an answer
    // for this question (regardless of whether that answer is correct)
    public boolean hasBeenAnswered ()
        return (userAnswer != null);
    // Private helper method to convert all answers to single lowercase
    // letters (in this case, 't' for TRUE and 'f' for FALSE)
    private char normalize (String input)
         if (input != null)
              input = input.trim(); // Remove leading whitespace
              input = input.toLowerCase();
              return input.charAt(0);
         else
              return ' ';
import java.util.*;
* This class represents a complete test or quiz.
* Data stored:
* - List of questions
* - Total score earned
* - Total score possible
* - Name/title of test
* - Instructions
*  - Category/class assignment
*  - Student (test-taker) name
*  - Date test is/was taken
*  - Time started
*  - Time completed
*  - Maximum time allotted
*  - (List of) Maximum attempts per question
*  - List of attempts per question
*  - List of difficulty ratings per question
*  - Assignment weight
* Methods:
* - Constructor
* - Add question
* - Display question
* - Display test
* - Display instructions
*      - Generate random exam
* - Take/administer test
* - Get score
* STUFF TO DO:
* - Add time/date restrictions
* - Add network access restrictions
* - Add other restrictions/allowances?
* @author (your name)
* @version (a version number or a date)
public class Test
    // Class constant
    public static final int MAX_NUMBER_OF_QUESTIONS = 10;
    // Class instance variables
    private String testName;
    private int scoreEarned; // What the student earned on the exam
    private int scorePossible; // Total point values of all questions
    private String instructions; // Exam header text
    private ArrayList<TrueFalseQuestion> questions; // Create inside constructor
    // Methods
    public Test (String name, String instr)
        testName = name;
        scoreEarned = 0;
        scorePossible = 0;
        instructions = instr;
        questions = new ArrayList<TrueFalseQuestion>(); //[MAX_NUMBER_OF_QUESTIONS];
    public String getInstructions()
        return instructions;
    public int getScore()
        return scoreEarned;
    public void addQuestion (TrueFalseQuestion q)
        scorePossible += q.getPointsValue();
        questions.add(q); // Automatically append question to end of test
    public String displayQuestion (int position)
        if (position < questions.size())
            return (position+1) + ". " + questions.get(position).getQuestion();
        else
            return null;
    public String displayTest ()
        String result = "";
        for (int i = 0; i < questions.size(); i++)
            result += (i+1) + ". (";
            TrueFalseQuestion t = questions.get(i);
            result += t.getPointsValue();
            result += " points)\n\n" + displayQuestion(i);
            result += "\n\n";
        return result;
    // Get test length (number of questions)
    public int length ()
         return questions.size();
    // Submit answer to a specific question
    public boolean answer(int number, String a)
         // Question numbers run from 0-(max-1) -- THIS WAS AN OFF-BY-ONE ERROR AT FIRST
         if (number >= 0 && number < questions.size())
              TrueFalseQuestion t = questions.get(number);
              t.submitAnswer(a);
              return true; // Question was answered
         else
              return false; // Unable to answer (nonexistent) question
    // Score exam
    public void scoreExam (boolean useNoBS)
         scoreEarned = 0;
         for (int i = 0; i < questions.size(); i++) // For each question in exam
              TrueFalseQuestion t = questions.get(i); // get current question
              scoreEarned += t.getPointsEarned(useNoBS);
}// Test harness for the Test and *Question classes
import java.util.*;
public class QuizDriver
     public static void main(String[] args)
          // Create a new Test object
          Test exam = new Test("Sample Exam", "Select the correct answer for each question");
          setUp(exam);
          Scanner sc = new Scanner(System.in);
          System.out.println(exam.getInstructions());
          // Administer exam
          for (int i = 0; i < exam.length(); i++)
               // Print out current question
               System.out.println(exam.displayQuestion(i));
               // Get user answer
               System.out.print("Your answer: ");
               String ans = sc.nextLine();
               if (ans.equals("")) // Handle blank responses for unanswered questions
                    ans = null;
               exam.answer(i, ans);
          // Get exam results
          exam.scoreExam(true);
          System.out.println("Your final score was " + exam.getScore() + " points.");
     private static void setUp (Test t)
          TrueFalseQuestion x = new TrueFalseQuestion("The sky is blue.", "true", 2);
          t.addQuestion(x);
          x = new TrueFalseQuestion("The first FORTRAN compiler debuted in 1957", "true", 5);
          t.addQuestion(x);
          x = new TrueFalseQuestion("Spock was a Vulcan", "false", 3);
          t.addQuestion(x);
}This program is far from finishing.
I have many questions about this program, but let me ask this one first:
In the TrueFalseQeustion class, why are there so many constructors? What is the purpose of setting some of the variables to default values?
Thank you very much!!!
Edited by: Terry001 on Apr 16, 2008 10:02 AM

Answer 1

newark wrote:
Stop ignoring the error messages. You seem to think that an error message means you're doing the assignment wrong. It's probably a simple fix. Post the exact error messages, as well as the code that corresponds to them. The error message will tell you exactly what line the problem occurs on, so you know right where to look.Hi,
After some modifications, the program now gives me the result the assignment wants when I run it. But I still have trouble with the MultipleChoiceQuestion class
Here is the complete program
QuizDriver class
// Test harness for the Test and *Question classes
import java.util.*;
public class QuizDriver
     public static void main(String[] args)
          // Create a new Test object
          Test exam = new Test("Sample Exam", "Select the correct answer for each question");
          setUp(exam);
          Scanner sc = new Scanner(System.in);
          System.out.println(exam.getInstructions());
          // Administer exam
          for (int i = 0; i < exam.length(); i++)
               // Print out current question
               System.out.println(exam.displayQuestion(i));
               // Get user answer
               System.out.print("Your answer: ");
               String ans = sc.nextLine();
               if (ans.equals("")) // Handle blank responses for unanswered questions
                    ans = null;
               exam.answer(i, ans);
          // Get exam results
          exam.scoreExam(true);
          System.out.println("Your final score was " + exam.getScore() + " points.");
     private static void setUp (Test t)
                               Question x;
          x = new TrueFalseQuestion("The sky is blue.", "true", 2);
          t.addQuestion(x);
          x = new TrueFalseQuestion("The first FORTRAN compiler debuted in 1957", "true", 5);
          t.addQuestion(x);
          x = new TrueFalseQuestion("Spock was a Vulcan", "false", 3);
          t.addQuestion(x);
          x = new MultipleChoiceQuestion("What is the color of the car\na.Red\nb.Green", "a. Red", 3);
          t.addQuestion(x);
          x = new MultipleChoiceQuestion("What is the name of this class\na.CSE110\nb.CSE114", "b, CSE114", 3);
          t.addQuestion(x);
}Test
public class Test
    // Class constant
    public static final int MAX_NUMBER_OF_QUESTIONS = 10;
    // Class instance variables
    private String testName;
    private int scoreEarned; // What the student earned on the exam
    private int scorePossible; // Total point values of all questions
    private String instructions; // Exam header text
    private ArrayList<Question> questions; // Create inside constructor
    // Methods
    public Test (String name, String instr)
        testName = name;
        scoreEarned = 0;
        scorePossible = 0;
        instructions = instr;
        questions = new ArrayList<Question>(); //[MAX_NUMBER_OF_QUESTIONS];
    public String getInstructions()
        return instructions;
    public int getScore()
        return scoreEarned;
    public void addQuestion (Question q)
        scorePossible += q.getPointsValue();
        questions.add(q); // Automatically append question to end of test
    public String displayQuestion (int position)
        if (position < questions.size())
            return (position+1) + ". " + questions.get(position).getQuestion();
        else
            return null;
    public String displayTest ()
        String result = "";
        for (int i = 0; i < questions.size(); i++)
            result += (i+1) + ". (";
            Question t = questions.get(i);
            result += t.getPointsValue();
            result += " points)\n\n" + displayQuestion(i);
            result += "\n\n";
        return result;
    // Get test length (number of questions)
    public int length ()
         return questions.size();
    // Submit answer to a specific question
    public boolean answer(int number, String a)
         // Question numbers run from 0-(max-1) -- THIS WAS AN OFF-BY-ONE ERROR AT FIRST
         if (number >= 0 && number < questions.size())
              Question t = questions.get(number);
              t.submitAnswer(a);
              return true; // Question was answered
         else
              return false; // Unable to answer (nonexistent) question
    // Score exam
    public void scoreExam (boolean useNoBS)
         scoreEarned = 0;
         for (int i = 0; i < questions.size(); i++) // For each question in exam
              Question t = questions.get(i); // get current question
              scoreEarned += t.getPointsEarned(useNoBS);
}Question
public class Question
// Class constants
  public static final int MIN_DIFFICULTY_LEVEL = 1;
  public static final int MAX_DIFFICULTY_LEVEL = 5;
  public static final int DEFAULT_DIFFICULTY_LEVEL = 1;
  public static final int DEFAULT_POINT_VALUE = 1;
  public static final String DEFAULT_CATEGORY_VALUE = "none";
  // Class instance variables
  protected String questionText;
  protected String correctAnswer;
  protected String userAnswer;
  protected int pointsValue;
  protected String category;
  protected int difficultyLevel; //TODO: set a range for difficulty levels
  // Constructors
  public Question (String text, String answer, int pts, String ctgry, int level)
      questionText = text.trim();
      correctAnswer = answer.trim();
      userAnswer = null;
      if (pts >= 1)
          pointsValue = pts;
        else
            pointsValue = DEFAULT_POINT_VALUE;
        category = ctgry.trim();
        if (level >= MIN_DIFFICULTY_LEVEL && level <= MAX_DIFFICULTY_LEVEL)
            difficultyLevel = level;
        else
            difficultyLevel = DEFAULT_DIFFICULTY_LEVEL;
    // Overloaded (simplied) constructors
    public Question (String text, String answer, int pts)
        this(text, answer, pts, DEFAULT_CATEGORY_VALUE, DEFAULT_DIFFICULTY_LEVEL);
    public Question (String text, String answer, int pts, String ctgry)
        this(text, answer, pts, ctgry, DEFAULT_DIFFICULTY_LEVEL);
    public Question (String text, String answer, String ctgry)
        this(text, answer, DEFAULT_POINT_VALUE, ctgry, DEFAULT_DIFFICULTY_LEVEL);
    public Question (String text, String answer, int pts, int level)
        this(text, answer, pts, DEFAULT_CATEGORY_VALUE, level);
    // Methods
    public String getQuestion ()
        return questionText;
    // Use this method to store user answers
    public void submitAnswer (String ans)
        userAnswer = ans;
    public boolean answerIsCorrect (String userAns)
        if (userAns == null)
            return false;
        else
            // Normalize and compare answers
            char key = normalize (correctAnswer); //Get the first letter of an answer
            char ans = normalize (userAns); //Get the first letter of an answer
            return (key == ans);
    public boolean answerIsCorrect ()// Why do we need two answerisCorrect() methods?
        return answerIsCorrect (userAnswer);
    public int getPointsValue ()
        return pointsValue;
    public int getPointsEarned (boolean userNoBSRule)
        System.out.println ("useNoBS: " + userNoBSRule + "\tuseAnswer: " + userAnswer + "\tcorrectAnswer: " + correctAnswer);
        if (userNoBSRule && (userAnswer == null))
            return 1;
        else if (userAnswer == null)
            return 0;
        if (answerIsCorrect() == false)
            return 0;
        else
            return pointsValue;
    public String getCorrectAnswer ()
        return correctAnswer;
    public boolean hasBeenAnswered ()
        return (userAnswer != null);
    private char normalize (String input)
        if (input != null)
            input = input.trim();
            input = input.toLowerCase();
            return input.charAt(0);
        else
            return ' ';
       TrueFalseQuestion
public class TrueFalseQuestion extends Question
  public TrueFalseQuestion (String text, String answer, int pts, String ctgry, int level)
      super(text, answer, pts, ctgry, level);
    public TrueFalseQuestion (String text, String answer, int pts)
        super(text, answer, pts, DEFAULT_CATEGORY_VALUE, DEFAULT_DIFFICULTY_LEVEL);
    public TrueFalseQuestion (String text, String answer, int pts, String ctgry)
        super(text, answer, pts, ctgry, DEFAULT_DIFFICULTY_LEVEL);
    public TrueFalseQuestion (String text, String answer, String ctgry)
        super(text, answer, DEFAULT_POINT_VALUE, ctgry, DEFAULT_DIFFICULTY_LEVEL);
    public TrueFalseQuestion (String text, String answer, int pts, int level)
        super(text, answer, pts, DEFAULT_CATEGORY_VALUE, level);
    // Methods
    public String[] getPossibleAnswerChoice ()
        String[] possibleAnswerChoice = {"true", "false"};
        return possibleAnswerChoice;
} MultipleChoiceQuestion
public class MultipleChoiceQuestion extends Question
   public MultipleChoiceQuestion (String text, String answer, int pts, String ctgry, int level)
       super(text, answer, pts, ctgry, level);
    public MultipleChoiceQuestion (String text, String answer, int pts)
        super(text, answer, pts, DEFAULT_CATEGORY_VALUE, DEFAULT_DIFFICULTY_LEVEL);
    public MultipleChoiceQuestion (String text, String answer, int pts, String ctgry)
        super(text, answer, pts, ctgry, DEFAULT_DIFFICULTY_LEVEL);
    public MultipleChoiceQuestion (String text, String answer, String ctgry)
        super(text, answer, DEFAULT_POINT_VALUE, ctgry, DEFAULT_DIFFICULTY_LEVEL);
    public MultipleChoiceQuestion (String text, String answer, int pts, int level)
        super(text, answer, pts, DEFAULT_CATEGORY_VALUE, level);
    // Methods
    String possibleAnswers;
    public String getPossibleAnswers ()
        return possibleAnswers;
    public void addAnswerChoice (String answerChoice)
        String ansChoice = answerChoice;
        questionText += "\nansChoice";
        possibleAnswers = answerChoice;
    public void printAnswerChoice ()
        System.out.println (questionText);
} I don't understand why the assignment wants me to build a method in the MultpleChoiceQuestion class to store the potential answer choices, I can make the program display the potential answer choices by including them in the questionText as following in the QuizDriver class
Question x;
x = new MultipleChoiceQuestion("What is the color of the car\na.Red\nb.Green", "a. Red", 3);
t.addQuestion(x); I don't know how to allow the client to construct the list of answer choices one at a time(add one potential answer choice by calling the addAsnwerChoices() method once)
Here are a few original sentences of my assignment which describe what I should do with the MultipleChoiceQuestion class
Using TrueFalseQuestion as a model, develop a new MultipleChoiceQuestion class that can be used to represent a problem where the user must select one of several answer choices (e.g., "Select answer (a), (b), (c), or (d)."). This new question type should have all of the same externally-visible functionality as TrueFalseQuestion, except that it must:
maintain a list of potential answer choices
provide a method that allows the client to construct the list of answer choices one at a time (i.e., the client should be able to call an addAnswerChoice() method to pass a new answer option to the MultipleChoiceQuestion.)
display (as part of the question text) the list of answer choices with appropriate letters ("abcd" instead of "0123") I don't understand what these sentences mean.
1. "Maintain a list of potential answer choices"-- this reminds me of the getPossibleAnswerChoice() method in the TrueFalseQuestion class
public String[] getPossibleAnswerChoice ()
        String[] possibleAnswerChoice = {"true", "false"};
        return possibleAnswerChoice;
    }I wonder that if the potential answer choices I have to store in the MultipleChoiceQuestion class are only letters "a", "b", "c", "d", etc, or include the answer text coming after the letters(eg. a.Red, b.Green)
2. "provide a method that allows the client to construct the list of answer choices one at a time". How do I achieve the functionality "one at a time"? Do I need to pass the input of the client (a potential answer choice) to the variable of the method which stores the list of potential answers?
3. "display (as part of the question text) the list of answer choices with appropriate letters". My question here is that: When the client type in one possible answer, should I append it to the variable questionText? (So I use the questionText variable in the methods of the first and second steps)
Thank you very much for your nice help!
Edited by: Terry001 on Apr 21, 2008 8:01 AM