Java - 如何在我的程序中显示我的每个成绩的字母成绩，而不仅仅是我的最后一个成绩？

Question

In my assignment for college, I have to prompt for a grade and get user input 6 times, then display each mark with a letter grade alongside it, and then display the average. I was finally able to get each mark to display right, but the letter grade for the last entry shows for every entry. What do I need to change in my code for this to work?

I have a method to return a letter grade, but the method only partially works; like it displays an appropriate letter grade, but only for the last entry.

package com.company;

import java.util.Scanner; //Summons the Scanner class

public class Main { //Main class

    //Instance variables to count and calculate the grades
    public static double total;
    public static int grade;
    public static int entries = 0;

    public static void main(String[] args) { //Main method

        //Creates a scanner for user input
        Scanner keyboard = new Scanner(System.in);
        int[]grades = new int[7];

        while (entries < 6) { //Make the user enter 6 grades
            do {
                System.out.printf("Enter grade %d: ", entries); //Prompt for a grade
                grades[entries] = grade;
                entries++;
                grade = keyboard.nextInt(); //Get the user input
                total = total + grade; //Add grade to total
            } while (!wrongValue(grade)); //Call a method to prompt for a re-entry upon user error
        }
        grades[6]=grade;
        double average = total / 6; //Get the total
        System.out.printf("1st grade is %d which is %s%n%%", grades[1], letterGrade(grade));
        System.out.printf("2nd grade is %d which is %s%n%%", grades[2], letterGrade(grade));
        System.out.printf("3rd grade is %d which is %s%n%%", grades[3], letterGrade(grade));
        System.out.printf("4th grade is %d which is %s%n%%", grades[4], letterGrade(grade));
        System.out.printf("5th grade is %d which is %s%n%%", grades[5], letterGrade(grade));
        System.out.printf("6th grade is %d which is %s%n%%", grades[6], letterGrade(grade));
        System.out.printf("total average = %.1f%%", average);
    }

    public static String letterGrade (int grade)
    {
        if (grade >= 90 && grade <= 100)
            return "an A+";
        else if (grade >= 80 && grade <= 90)
            return "an A";
        else if (grade >= 75 && grade <= 80)
            return "a B+";
        else if (grade >= 70 && grade <= 75)
            return "a B";
        else if (grade >= 65 && grade <= 70)
            return "a C+";
        else if (grade >= 60 && grade <= 65)
            return "a C";
        else if (grade >= 55 && grade <= 60)
            return "a D+";
        else if (grade >= 50 && grade <= 55)
            return "a D";
        else
            return "an F";
    }
}

Answer 1

I suspect you wanted to call letterGrade with each grade you read from the user. But first, arrays start at 0 (not 1 ). Your format String (s) had odd %% literal(s) which would start over on the next line, and I cleaned up the code a bit (I'm not a fan of temporary variables that serve no purpose, nor do I like comments that fail to clarify the code). Like,

public static void main(String[] args) {
    Scanner keyboard = new Scanner(System.in);
    int[] grades = new int[6];
    int total = 0;
    for (int i = 0; i < grades.length; i++) {
        do {
            System.out.printf("Enter grade %d: ", i + 1);
            grades[i] = keyboard.nextInt();
        } while (!wrongValue(grades[i])); 
        total += grades[i];
    }
    double average = total / 6.0;
    System.out.printf("1st grade is %d which is %s%n", grades[0], letterGrade(grades[0]));
    System.out.printf("2nd grade is %d which is %s%n", grades[1], letterGrade(grades[1]));
    System.out.printf("3rd grade is %d which is %s%n", grades[2], letterGrade(grades[2]));
    System.out.printf("4th grade is %d which is %s%n", grades[3], letterGrade(grades[3]));
    System.out.printf("5th grade is %d which is %s%n", grades[4], letterGrade(grades[4]));
    System.out.printf("6th grade is %d which is %s%n", grades[5], letterGrade(grades[5]));
    System.out.printf("total average = %.1f which is %s%n", average, 
            letterGrade((int) average));
}

Finally, I assumed based on your posted logic that wrongValue actually returns true when the value is valid (so the method name seems to be backwards).