使用二維數組創建一個年級計算器

Question

我很難理解如何去做我的程序。該程序應該看起來像這樣：

Number of students: 3 

Number of exams : 3 

Enter student's data (first name follow by exam scores): 

Joe 85 88 93 

Mike 90 100 97 

Bill 50 68 73 

Name E1  E2  E3  Grade 


Joe 85  88  93  88.666666666667 

Mike 90  100 97  95.666666666667 

Bill 50  68  73  63.666666666664 

我在介紹Java課程，所以我剛剛學習了本週的數組。

我的代碼看起來像這樣到目前爲止。

import java.util.Scanner; 

public class GradeCalcWithArrays { 
    public static void main(String[] args) { 

     Scanner s = new Scanner(System.in); 
     int students = 0; 
     int exams = 0; 

     System.out.println("Number of students: "); 
     students = s.nextInt(); 
     String names[] = new String[students]; 

     System.out.println("Number of exams: "); 
     exams = s.nextInt(); 
     int scores[][] = new int[students][exams]; 

     for (int i, j = 0;;) { 
      System.out 
        .println("Enter student's data (first name followed by exams scores):"); 
      String studentnames = s.nextLine(); 
      studentnames = names[3]; 
      int e1 = s.nextInt(); 
      e1 = scores[0][0]; 
      int e2 = s.nextInt(); 
      e2 = scores[0][2]; 
      int e3 = s.nextInt(); 
      e3 = scores[0][3]; 

     } 

    } 
} 

我很想爲這些陣列提供一些幫助。我想我正在嘗試輸入一些東西。但是，一旦我到達老師所說的需要使用的雙數組，我就不知所措，我不知道如何去輸入數組。任何幫助深表感謝。

而且我的程序的輸出到目前爲止是：

Number of students: 3 

Number of exams: 3 

Enter student's data (first name follow by exam scores): 

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 3 
    at GradeCalcWithArrays.main(GradeCalcWithArrays.java:25) 

我使用Eclipse，如果這是如何幫助也給出一個因素。

Answer 1

數組索引從0開始。由於name是一個可容納3個元素的String數組，因此有效索引爲0-2。您嘗試在name[3]中存儲String（studentnames），這是一個無效的位置。因此，你會得到一個ArrayOutOfBounds異常。

所以代碼應該是：

import java.util.Scanner; 

public class GradeCalcWithArrays { 
    public static void main(String[] args) { 

     Scanner s = new Scanner(System.in); 
     int students = 0; 
     int exams = 0; 

     System.out.println("Number of students: "); 
     students = s.nextInt(); 
     String names[] = new String[students]; 

     System.out.println("Number of exams: "); 
     exams = s.nextInt(); 
     int scores[][] = new int[student][exams]; 

     for (int i = 0;i<students; i++) { 
      System.out.println("Enter student "+ i+1 +" data (first name followed by exams scores):"); 
      names[i] = s.nextLine(); 

      for(int j=0;j<exams;j++) 
      { 
       scores[i][j] = s.nextInt(); 
      } 

     } 
    //Rest of your code to print the table goes here 
    } 
}