我是新來的Java，我工作的一個項目，但我似乎無法得到for循環右

Question

public static void main(String[] args) { 

    Scanner s = new Scanner(System.in); 
    System.out.println("Welcome to GradeCalculator!"); 
    System.out.println("\nPlease enter the number of students: "); 
    int numberOfStudent = s.nextInt(); 
    System.out.println("Please enter the number of exams: "); 
    int numberOfExams = s.nextInt(); 
    System.out.println(); 

    //outer loop for the number of students 
    for (int i = 1; i <= numbeOfStudent; i++) { 
     System.out.println("----------------------------------------"); 
     System.out.println("Enter student " + i + "'s " + "name: "); 
     String name = s.nextLine(); 
     s.next(); 
    } 
    System.out.println(); 

    //inner loop for the number of exams scores entered 
    int sum = 0; 
    for (int j = 1; j <= numberOfExam; j++) { 
     System.out.print("Enter exam scores: "); 
     double examScore = s.nextDouble(); 
     sum += examScore; 

     if (examScore < 0) { 
      System.out.println("Invalid exam scores, reenter: "); 
      double examScoreReenter = s.nextDouble(); 
      sum += examScoreReenter; 
     } else { 
      System.out.println(); 
     } 
    } 
} 

---

控制檯輸出：

Welcome to GradeCalculator! 

Please enter the number of students: 
2 
Please enter the number of exams: 
3 

---------------------------------------- 
Enter student 1's name: 
john smith 
---------------------------------------- 
Enter student 2's name: 
jane smith 

Enter exam scores: "get exception" 
------------------------------------------------------------------------ 

我一直在掙扎現在這個好幾天了，我想不出來。我想要的輸出是這樣的：

------------------------- 
Enter student 1's name : 
Enter exam score: 
Invalid exam scores, reenter: 
------------------------- 

任何建議將不勝感激。

Answer 1

如果輸入一個無效的double，如「thisisastringnotanumber」，則爲InputMismatchException is thrown。你應該用try塊來包圍你的nextDouble（）調用來適應這個。

for (int j = 1; j <= numberOfExam; j++) { 
    System.out.print("Enter exam scores: "); 
    try{ 
     double examScore = s.nextDouble(); 

     if (examScore < 0) { 
      System.out.println("Invalid exam scores, reenter: "); 
      j--; //Retry this iteration 
     } else { 
      sum += examScore; 
      System.out.println(); 
     } 
    }catch(InputMismatchException e){ 
     System.out.println("Invalid exam scores, reenter: "); 
     j--; //Retry this iteration 
    } 
}