Thread: Need help using interfaces

The instructions for this program are to find a way to make it display both the letter grade and the score but I have no idea how to do it without completely defeating the point of the interface. If anyone knows a way to do this I would really appreciate the help.

public class Quiz implements Measurable
{
    public Quiz(double initialScore, String initialLetter)
    {
        score = initialScore;
        letter = initialLetter;
    }
    public Object measure()
    {
        return score;
    }
    public Object measure2()
    {
        return letter;
    }
    private double score;
    private String letter;
}
 
public interface Measurable
{
    Object measure();
}
 
public class DataSet
{
   public DataSet()
   {
       sum = 0;
       i = 0;
       maximum = null;
   }
   public void add(Measurable x)
   {
       sum += (double) x.measure();
       if (i == 0 || (double) maximum.measure() < (double) x.measure())
       {
           maximum = x;
       }
       i++;
   }
   public double getAverage()
   {
       return sum / i;
   }
   public Measurable getMaximum()
   {
       return maximum;
   }
   private Measurable maximum; 
   private double sum;
   private int i; 
}
 
public class DataSetTester
{
    public static void main(String[] args)
    {
        DataSet data = new DataSet();
 
        data.add(new Quiz(.98, "A"));
        data.add(new Quiz(.90, "A"));
        data.add(new Quiz(.85, "B"));
        data.add(new Quiz(.28, "F"));
        data.add(new Quiz(.91, "A"));
 
        System.out.println(data.getAverage());
        System.out.println(data.getMaximum().measure());
    }
}

What happens when you compile the program? If there are errors, copy the full text and paste it here.
What is the program supposed to do? Where are the values to be displayed? What code is supposed to display them? Why does the method in the interface return an Object? What is in the object?

Please edit your post and wrap your code with code tags:

[code]
**YOUR CODE GOES HERE**
[/code]

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The program works this is the output:
0.784
0.98

I just need to figure out how to get the letter grade into the output through the dataset. The exact instructions are as follows: Define a class Quiz that implements the Measurable interface. A quiz has a score and a letter grade (such as B+). Use the first implementation of the DataSet class to process a collection of quizzes. Display the average score and the quiz with the highest score (both letter grade and score).

What is supposed to be in the Object returned by measure? Why does the method return an Object instead of a specific class that has useful data and methods?

Yes, I have a reasonable understanding of what an interface is and how to use it.

My question is about the Measurable interface. What is it supposed to do? How and why would it be used?
Method names should be verbs describing what the method does. What is being measured by the measure method?

measure method is measuring the fundamental data that is inputted rather than looking at specifics of the measurement. It's basically just looking at what all measurable objects have in common for the sake of reducing coupling and making the code reusable.

How does it do that? Your description is generic and could apply to lots of methods.
What does it return after doing all that?