array of counters-histogram

package class170629;

import java.util.Random;
import java.util.Scanner;

public class arrayHistogram {

    public static void main(String[] args) {
        /*
         * histogram
         * input: grades of students. until the first invalid grade
         * output: the number of grades, and a histogram of grades
         */

        // create a scanner
        Scanner s = new Scanner(System.in);

        // array for counting grades
        // 0 for 0-9, 1 for 10-19, ... , 9 for 90-99, 10 for 100
        int[] count = new int[11];
        for (int i = 0; i < count.length; i += 1) {
            count[i] = 0; // initialize counter
        }
        int total = 0; // total number of students

        // data source
        char dataSource; // auto=computer or manual=user;
        do {
            System.out
                    .println("select data source ('m' for manual, 'a' for auto): ");
            dataSource = s.next().charAt(0);
        } while (dataSource != 'a' && dataSource != 'A' && dataSource != 'm'
                && dataSource != 'M');

        if (dataSource == 'a' || dataSource == 'A') {
            // computer select number of students and their grades
            Random rnd = new Random();
            total = 20 + rnd.nextInt(980); // number of students: 20 to 999

            for (int i = 0; i < total; i += 1) {
                int grade = rnd.nextInt(101); // get random grade
                count[grade / 10] += 1; // update counter
            }
        } else {
            // read grades from the user
            System.out
                    .println("Enter grades of students (1 to 100), or any other number to exit: ");
            do {
                int grade = s.nextInt();
                // if invalid grade
                if (grade < 0 || grade > 100) {
                    // then stop
                    break;
                }

                // else
                count[grade / 10] += 1;
                total += 1;

            } while (true);
            s.close();
        }

        // printing results
        System.out.println("distribution of the grades:");
        System.out.println("+-----------+-----+--------+");
        System.out.println("|   Range   | No. |    %   |");
        System.out.println("+-----------+-----+--------+");
        for (int i = 0; i < count.length; i += 1) {
            int rangeFrom = 10 * i;
            int rangeTo = i == 10 ? 10 * i : 10 * (i + 1) - 1;
            double percent = 100 * count[i] / (double) total;

            System.out.printf("| %3d - %3d | %3d | %6.2f |\n", rangeFrom,
                    rangeTo, count[i], percent);
            System.out.println("+-----------+-----+--------+");
        }
        System.out.printf("Total number of students is %d\n", total);

    }
}