java - do while 循环重复两次，不遵循条件

Question

我是 Java 新手，遇到了一些问题。我的导师要求我在 while 循环中嵌套 do while 循环； do while 循环对用户可以输入的期中、期末和项目成绩的成绩类型(大于 0 但小于 100)进行限制。然后，该输入用于计算这三个成绩的平均值。

但是，我的 do while 循环运行两次，并在计算平均值时使用第二个提示的输入。我究竟做错了什么？我已经浏览了我的教科书和这个网站，但我似乎无法理解它为什么这样做，因为它只提示两次，然后只使用第二次提示的输入。任何帮助将不胜感激。感谢您花时间阅读我的帖子!

为了澄清起见，这是我的代码:

System.out.println("******** Step 2: Grading for Multiple Students *********");
    System.out.println();
    // Create scanner object for text and number
    Scanner textReader = new Scanner(System.in);
    Scanner numberReader = new Scanner(System.in);
    System.out.print("Would you like to input grades (y/n): ");
    String response = textReader.nextLine();
    // Create while loop for first yes/no question
    while ((!response.equalsIgnoreCase("y")) && (!response.equalsIgnoreCase("n")))
    {
        System.out.print("y/n needed: ");
        response = textReader.nextLine();
        System.out.println();
    }
    while ((response.equalsIgnoreCase("y")))
    {
        System.out.print("\nStudent Name: ");
        String studentName = textReader.nextLine();
        System.out.print("Course Name: ");
        String courseName = textReader.nextLine();
        System.out.print("Midterm Grade (needs to be between 0-100): ");
        double midtermGrade = numberReader.nextDouble();
        do
        {
            System.out.print("Midterm Grade (needs to be between 0-100): ");
            midtermGrade = numberReader.nextDouble();
            break;
        }
        while ((midtermGrade < 0) || (midtermGrade > 100));
        System.out.print("Final Grade (needs to be between 0-100): ");
        double finalGrade = numberReader.nextDouble();
        do
        {
            System.out.print("Final Grade (needs to be between 0-100): ");
            finalGrade = numberReader.nextDouble();
        }
        while ((finalGrade < 0) || (finalGrade > 100));
        System.out.print("Project Grade (needs to be between 0-100): ");
        double projectGrade = numberReader.nextDouble();
        do
        {
            System.out.print("Project Grade (needs to be between 0-100): ");
            projectGrade = numberReader.nextDouble();
        }
        while ((projectGrade < 0) || (projectGrade > 100));

这是我的输出:

Output link

Answer 1

在 do-while 循环中，无论条件如何，循环至少被调用一次。在普通的 while 循环中，只有满足条件时才会调用循环。

而不是

System.out.print("Final Grade (needs to be between 0-100): "); // remove this
double finalGrade = numberReader.nextDouble(); // remove this
do
{
   System.out.print("Final Grade (needs to be between 0-100): ");
   finalGrade = numberReader.nextDouble();
}
while ((finalGrade < 0) || (finalGrade > 100));

只需为每个输入循环删除上述代码片段的前两行即可。