/*
 * T01n20.java -- Using an array, computes the sum and average of a group
 * of exam scores.  Things to note:
 *
 *   (1) Modular design (that is, use of appropriate methods and parameters)
 *       
 *   (2) A demonstration (in the method fetchScores) of passing in an
 *       existing array and populating it.  The following example program
 *       shows a different approach.
 *
 *   Notice that main() and computeAverage() both call computeSum().  Yes,
 * this means that we are wasting time computing the sum twice, but it's
 * also logical; when some part of the program needs the sum, it calls
 * computeSum() to get it.  There are some tricks we could play to get
 * the sum just once for both uses, but it's clearer the way it is.
 * (Remember, for most programming, you'd rather sacrifice a little efficiency
 * for an understandable, reliable solution (and thus easier maintenance).
 */

import java.util.*;

public class T01n20
{
    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
        int[]  scores;          // the collection of scores

        scores = new int[MAX_SCORES];

        numberOfScores = fetchScores(scores);
        totalOfScores = computeSum(scores,numberOfScores);
        average = computeAverage(scores,numberOfScores);

        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");
        }
    }


    private static int fetchScores (int[] list)
    {
        int numberOfScores = 0;   // Haven't seen any scores yet
        Scanner keyboard = new Scanner (System.in);  // source of user input

                // Continue accepting scores until the array is full
                // or the user enters -1.  Note that we're changing the
                // content of the array, which is the same array that main()
                // created.  Thus, no need to return the array.

        do {
            System.out.print("Enter a score (-1 to quit): ");
            list[numberOfScores++] = keyboard.nextInt();
        } while (numberOfScores < MAX_SCORES && list[numberOfScores-1] != -1);

                // Adjust the quantity of scores stored if -1 was entered

        if (list[numberOfScores-1] == -1)
            numberOfScores--;

        return numberOfScores;
    }

    private static double computeAverage (int[] list, int quantity)
    {
        int total;  // holds the sum of the scores

        total = computeSum(list,quantity);
        return (double)total/quantity;
    }

    private static int computeSum (int[] list, int quantity)
    {
        int runningTotal = 0;  // accumulates the sum

        for (int i = 0; i < quantity; i++) {
            runningTotal += list[i];
        }

        return runningTotal;
    }

}