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The fundamental object of a Quiz Generator app is a Question. A question of an MCQ quiz is composed of 3 main parts:

Question Title
Question Options
Question Answer

To treat all 3 of these features as a single unit, we need a class.

Initial design of class, Question:

public class Question {
    // Fields
    String title;
    String options;
    String answer;
}

As per Object-Oriented Programming (OOP) concept, Encapsulation, fields of a class must be hidden and the data stored by them must be exposed through their respective public accessors (getters) and mutators (setters).

Let’s apply that:

public class Question {
    // private Fields
    private String title;
    private String options;
    private String answer;
    // public Accessor Methods
    public String getTitle() {
        return title;
    }
    public String getOptions() {
        return options;
    }
    public String getAnswer() {
        return answer;
    }
    // public Mutator Methods
    public void setTitle(String title) {
        this.title = title;
    }
    public void setOptions(String options) {
        this.options = options;
    }
    public void setAnswer(String answer) {
        this.answer = answer;
    }
}

It’s a good practice to always test the code as soon as some new features or behaviors are updated in the source code. While writing test code for your class, it is suggested that you always write expected result along with any print statements. That way, you can check if your code is giving a result as you already expected. Let’s try testing our code with a Tester class:

public class QuestionTester {
    public static void main(String[] args) {
        // 1. Create an instance of the class we are testing
        Question q1 = new Question();
        System.out.println("Question Title" + q1.getTitle());
        System.out.println("Expected: null");
        System.out.println("Question Options" + q1.getOptions());
        System.out.println("Expected: null");
        System.out.println("Question Answer" + q1.getAnswer());
        System.out.println("Expected: null");
    }
}

Question

Why do you think results of each of these fields are null?

Answer

As we did not provide any constructor in the class, an implicit default constructor is provided and it looks like the following:

  public Question() {
    title = null;
    options = null;
    answer = null;
  }

This default constructor initializes all the fields with default values of their respective types.

Continue to the next topic if you are clear about the above question.

Adding a Constructor