Java gradeCalculator-while循环工作不正常

Question

我正在编写一个程序，用户输入一个班级中的学生人数、该班级参加的考试次数，然后输入每个学生的姓名和考试分数。然后，程序计算学生的成绩，并分配给他们一个相应的字母等级。然后最后，它将他们的分数添加到一个classSum，计算平均类分数并显示出来。

这就是我目前所拥有的：public class GradeCalculator{

    public static void main(String[] args) {
        int classSum = 0;       // variable used to hold sum of entire classes exams
        int classExams = 0;     // variable used to hold number of exams taken by whole class

        Scanner s = new Scanner(System.in);

        System.out.println("Welcome to Gradecalculator!");
        System.out.println("Please enter the number of students:");
        int students = s.nextInt();

        System.out.println("Please enter the number of exams:");
        int exams = s.nextInt();   

        int i = 0;
        int studentnumber = 1;
        int sum = 0;

        while (i < students) {    // loop until it matches number of students entered above
            i++;
            sum = 0;

            System.out.println("Enter student " + studentnumber++ + "'s name :");
            String studentname = s.next();

            System.out.println("Enter exam scores :");

            int input = 0;
            for (; input < exams; input++) {   
                int n = s.nextInt();
                sum+=n;

                if (n < 0) {
                    System.out.println("Invalid exam scores, reenter: ");  //if one of the scores entered is     negative, display message
                }
            }

            double average = sum/exams;        // assign letter grade based on average of exams
            if (average <= 100 && average >= 90) {
                System.out.println("Letter grade: A");
                System.out.println(studentname + " gets 4 stars! ****");
            } if (average <= 89 && average >= 80) {
                System.out.println("Letter grade: B");
                System.out.println(studentname + " gets 3 stars! ***");
            } if (average <= 79 && average >= 70) {
                System.out.println("Letter grade: C");
                System.out.println(studentname + " gets 2 stars! **");
            } if (average <= 69 && average >= 60) {
                System.out.println("Letter grade: D");
                System.out.println(studentname + " gets 1 star! *");
            } if (average <= 59) {
                System.out.println("Letter grade: F");
                System.out.println(studentname + " gets 0 stars!");
            }

            classSum += sum;             // add sum of this student's scores to the classSum
            classExams += exams;   // add exams taken by this student to amount of exams taken by whole class
        }

        int classAverage = classSum/classExams; // compute class average
        System.out.println("Class statistics:");
        System.out.println("\tAverage: " + classAverage);
    }
}

这是我得到的输出：

Welcome to Gradecalculator!

Please enter the number of students:

2

Please enter the number of exams:

3

Enter student 1's name :

sam

Enter exam scores :

80 80 80

Letter grade: B

sam gets 3 stars! ***

Enter student 2's name :

joe

Enter exam scores :

90 90 90

Class statistics:

Average: 125

正如您所看到的，在第一个学生之后，输入姓名和考试分数并不像循环应该做的那样显示下一个学生的字母等级。此外，未正确计算类平均值。我对自己的错误有点不知所措。

Answer 1

您必须将循环的每一圈sum设置为0

while (i < students) { // loop until it matches number of students entered above
    i++;
    sum = 0;

    System.out.println("Enter student " + studentnumber++ + "'s name :"); String studentname = s.next();
    // [...]