GradeTester

import java.util.Scanner;

public class GraderTester {

    public static void main(String []args) {

        Scanner scan = new Scanner(System.in); // instantiate Scanner object
        int quizNumber = 1; // initialize beginning quizNumber for increment later
        double sumOfQuizScores = 0; // initialize for addition later
        double quizScore, finalExamScore;
        final int TOTALNUMBEROFQUIZZES = 4;

        System.out.println();

         do {
            System.out.printf("Enter the score for Quiz #%d: ", quizNumber);
            quizScore = scan.nextDouble();

            // this while loop validates input. Negative numbers are not accepted
            while (quizScore < 0) {
                System.out.println("Score cannot be negative.");
                System.out.printf("Enter the score for Quiz #%d: ", quizNumber);
                quizScore = scan.nextDouble();
            }

             sumOfQuizScores += quizScore;
             quizNumber++;
        } while (quizNumber <= TOTALNUMBEROFQUIZZES);

        // Ask for final exam score
        System.out.print("Enter final exam score: ");
        finalExamScore = scan.nextDouble();

        // Validate score, must be 0 or positive
        while (finalExamScore < 0) {
            System.out.println("Score cannot be negative.");
            System.out.print("Enter final exam score: ");
            finalExamScore = scan.nextDouble();
        }

        // define variables to store the return values of the static methods
        double averageOfQuizzes = getAverageOfQuizzes(sumOfQuizScores);
        double finalPercentageOfStudent = getFinalPercentage(averageOfQuizzes,finalExamScore);
        char finalLetterGradeOfStudent = getLetterGrade(finalPercentageOfStudent);

        System.out.printf("Student's Final Percentage: %,.2f\n", finalPercentageOfStudent);
        System.out.printf("Student's Letter Grade: %c\n", finalLetterGradeOfStudent);
    } // end main

    /**
     * Method that calculates the average score of 4 quizzes.
     * @param sum the sum of all 4 quiz scores entered.
     * @return average
     */
    public static double getAverageOfQuizzes(double sum) {

        return sum / 4;
    }

    /**
     * Method that calculates final percentage of student.
     * @param average the average of 4 quizzes
     * @param score final exam score
     * @return final percent score of student
     */
    public static double getFinalPercentage(double average, double score) {

        return (0.60 * average) + (0.40 * score);
    }

    /**
     * Method that calculates letter grade based on score.
     * @param score calculated total decimal score of 4 quizzes + 1 final exam
     * @return letter grade
     */
    public static char getLetterGrade(double score) {

        int quotient = (int) score / 10;

        switch (quotient) {
            case 10:
            case 9:
                return 'A';
            case 8:
                return 'B';
            case 7:
                return 'C';
            case 6:
                return 'D';
            default:
                return 'F';
        }
    }

} // end class