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。我的教师要求我在while循环中嵌套do while循环; do while循环会为中期，最终和项目等级的用户可输入的等级类型（大于0但小于100）创建限制。然后将此输入用于计算这三个等级的平均值。

但是，我的while while循环运行了两次，并使用来自计算中第二个提示的输入的平均值。我究竟做错了什么？我已经浏览了我的教科书和这个网站，但我似乎无法理解为什么它这样做，因为它只提示两次，然后只使用第二个提示的输入。任何帮助将不胜感激。感谢您花时间阅读我的文章！

为了清楚起见，这里是我的代码：

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)); 

这里是我的输出：

Output link

Answer 1

在do-while循环，该循环称为至少一次，无论的条件。 在正常的while循环中，只有满足条件时才会调用循环。

代替

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)); 

只需删除上述片断的前两行的每个输入回路。