Question

I’m writing a program that takes user input of five students and four test scores per student and puts them into arrays. It then averages the student’s scores and gives a letter grade. The program also needs an input validation that doesn’t accept scores under 0 and over 100.

So far my program validates the user and tells them that they’ve input an invalid number, but I would also like for it to prompt the user to start over after they’ve input an invalid number. I’ve tried a couple of different options as you will see below (in the enterData method), but none of which force the user to start over. Any suggestions?

import java.util.Scanner;

public class GradeBook {
    private String[] names = new String[5];

    private char[] grades = new char[5];

    private double[] scores1 = new double[5];
    private double[] scores2 = new double[5];
    private double[] scores3 = new double[5];
    private double[] scores4 = new double[5];
    private double[] scores5 = new double[5];

    int studentData = 0;
    int studentCount = 0;

    Scanner keyboard = new Scanner(System.in);

    public void enterData() {
        do {
            System.out.println("Enter the student's name:");
            String student = keyboard.nextLine();

            System.out.println("Enter the student's first test score");
            double score1 = Double.parseDouble(keyboard.nextLine());
            if (score1 > 0 || score1 < 100) {
            } else {
                System.out.println("Invalid number");
                continue;
            }


            System.out.println("Enter the student's second test score");
            double score2 = Double.parseDouble(keyboard.nextLine());
            if (score2 > 0 || score2 < 100) {
            } else {
                System.out.println("Invalid number");
                System.out.println("Please start over");
                continue;
            }

            System.out.println("Enter the student's third test score");
            double score3 = Double.parseDouble(keyboard.nextLine());
            if (score3 < 0 || score3 > 100)
                System.out.println("Invalid number");

            System.out.println("Enter the student's fourth test score");
            double score4 = Double.parseDouble(keyboard.nextLine());
            if (score4 < 0 || score4 > 100)
                System.out.println("Invalid number");

            addStudent(student, score1, score2, score3, score4);
            studentData++;
        } while (studentData < 5);
    }


    public String toString() {
        StringBuilder printout = new StringBuilder();
        for (int i = 0; i < names.length; i++) {
            if (names[i] == null)
                continue;
            printout.append("Student name: " + names[i] + "\t" + "Average test score: " +
                    getAverage(i) + "\t" + "Grade: " + grades[i] + "\n");
        }
        return printout.toString();
    }


    private void addStudent(String inName, double scr1, double scr2, double scr3, double scr4) {

        names[studentCount] = inName;
        scores1[studentCount] = scr1;
        scores2[studentCount] = scr2;
        scores3[studentCount] = scr3;
        scores4[studentCount] = scr4;
        grades[studentCount] = getLetterGrade(studentCount);
        studentCount++;
    }


    private double getAverage(int index) {
        double score1 = scores1[index];
        double score2 = scores2[index];
        double score3 = scores3[index];
        double score4 = scores4[index];
        double average = (score1 + score2 + score3 + score4) / 4.0;
        return average;
    }

    private char getLetterGrade(int index) {
        double average = getAverage(index);
        char grade;

        if (average >= 90)
            grade = 'A';
        else if (average >= 80)
            grade = 'B';
        else if (average >= 70)
            grade = 'C';
        else if (average >= 60)
            grade = 'D';
        else
            grade = 'F';


        return grade;
    }

}

I made this more difficult than needed. This works just fine.

   System.out.println("Enter the student's third test score");
    double score3 = Double.parseDouble(keyboard.nextLine());          
      while (score3 < 0 || score3 > 100)
      {
          System.out.println("Invalid score, plese reenter");
          System.out.println("Enter the student's third test score");
        score3 = Double.parseDouble(keyboard.nextLine());
      }

Answer 1

System.out.println("Enter the student's third test score");
double score3 = Double.parseDouble(keyboard.nextLine());          
  while (score3 < 0 || score3 > 100)
  {
      System.out.println("Invalid score, plese reenter");
      System.out.println("Enter the student's third test score");
    score3 = Double.parseDouble(keyboard.nextLine());
  }