/*
 * T01n21.java -- The object-oriented take on handling a collection of 
 * scores.
 * 
 * The collection of scores, and the operations that work on it, make a
 * nice object.  Here, we define the class Scores that supports
 * the fetchScores(), computeAverage(), and computeSum() methods, along
 * with a constructor, a couple of getters, and a setter.
 * 
 * I mixed in a lot of variety in how things get done.  For instance,
 * sometimes methods call other methods to get values, etc., and other
 * times they do it themselves.  In general, the calling approach is
 * best, to help isolate that specific task within one method; if that
 * task changes, we only have to change the implementation of that one
 * method.
 */

import java.util.*;

class Scores
{
    private int[] scores;          // the scores held by the object
    private int   numberOfScores;  // the # of elements holding valid scores
    private int   maxScores;       // the quantity of scores we can store

    public Scores (int quantity)
    {
        scores = new int[quantity];
        numberOfScores = 0;
        maxScores = quantity;
    }

    public int getScore(int index)
    {
        return scores[index];
    }

    public void setScore(int index, int value)
    {
        scores[index] = value;
    }

    public int getQuantity()
    {
        return numberOfScores;
    }

            /* Note that fetchScores() references a Scanner object created
             * by the application program.  This class doesn't know from
             * which source the scores will come from, so it shouldn't
             * be in charge of creating the Scanner object.  The application
             * knows; let it worry about the source.
             */

    public void fetchScores (Scanner keyboard)
    {
        numberOfScores = 0;               // make sure we have an empty list
      
        do {
            System.out.print("Enter a score (-1 to quit): ");
            this.setScore(numberOfScores++,keyboard.nextInt());
        } while (this.getQuantity() < maxScores 
                 && this.getScore(numberOfScores-1) != -1);

        if (this.getScore(numberOfScores-1) == -1)
            numberOfScores--;
    }

    public double computeAverage ()
    {
        int total;   // holds the sum of the scores

        total = this.computeSum();
        return (double)total/numberOfScores;
    }

    public int computeSum ()
    {
        int runningTotal = 0;  // accumulates the sum

        for (int i = 0; i < numberOfScores; i++) {
            runningTotal += scores[i];
        }

        return runningTotal;
    }

}

public class T01n21
{
    final static int MAX_SCORES = 10;

    public static void main (String [] args)
    {
        int     numberOfScores,  // quantity of scores entered by the user
                totalOfScores;   // sum of the entered scores
        double  average;         // mean of the scores
        Scores  collection;      // reference to the object holding the scores
        Scanner keyboard = new Scanner (System.in);  // source of user input

        collection = new Scores (MAX_SCORES);

        collection.fetchScores(keyboard);
        numberOfScores = collection.getQuantity();
        totalOfScores = collection.computeSum();
        average = collection.computeAverage();

        if (numberOfScores > 0) {
            System.out.printf("\nThere are %d scores that total to %d;\n"
                            + "the average for the class is %.2f.\n\n",
                            numberOfScores, totalOfScores, average);
        } else {
            System.out.println("\nYou entered no scores; there is"
                             + " no average.\n");
        }

    }
}