for循環中的java.lang.nullpointer異常

-1

我正在嘗試制定一個計劃，它使用Scanner類的用戶輸入。該計劃的重點是打印日程安排。在在makeSchedule功能循環，出現了一個java.lang.NullPointerException這行：for循環中的java.lang.nullpointer異常

System.out.print(blocks[numberSchedule[i][k] - 1] + "\t");

我測試了這行代碼的功能之外，它完美的工作沒有任何異常。

我不知道我在想什麼。

import java.util.Scanner; 

public class Schedule 
{ 
    public int[][] scheduleArray; 
    public static String A, B, C, D, E, F, G, H; 
    public static String[] blocks; 

    public static void main(String[] args) 

    { 
    Scanner kboard = new Scanner(System.in); 
    int[][] scheduleArray = new int[][] { {1, 2, 3, 1, 2, 3, 1, 2}, 
     {3, 1, 2, 3, 1, 2, 3, 4}, {4, 8, 6, 5, 7, 4, 8, 6}, 
     {8, 7, 4, 6, 5, 8, 5, 7}, {6, 5, 7, 8, 4, 6, 7, 5}}; 

    System.out.print("What is your A block class?"); 
    String A = kboard.nextLine(); 
    System.out.print("\n"); 
    System.out.print("What is your B block class?"); 
    String B = kboard.nextLine(); 
    System.out.print("\n"); 
    System.out.print("What is your C block class?"); 
    String C = kboard.nextLine(); 
    System.out.print("\n"); 
    System.out.print("What is your D block class?"); 
    String D = kboard.nextLine(); 
    System.out.print("\n"); 
    System.out.print("What is your E block class?"); 
    String E = kboard.nextLine(); 
    System.out.print("\n"); 
    System.out.print("What is your F block class?"); 
    String F = kboard.nextLine(); 
    System.out.print("\n"); 
    System.out.print("What is your G block class?"); 
    String G = kboard.nextLine(); 
    System.out.print("\n"); 
    System.out.print("What is your H block class?"); 
    String H = kboard.nextLine(); 
    System.out.print("\n"); 
    final String[] blocks = {A, B, C, D, E, F, G, H}; 

    makeSchedule(scheduleArray); 

    } 

    public static void makeSchedule(int[][] numberSchedule) 
    { 
    for (int i = 0; i < 5; i++) 
    { 
     for (int k = 0; k < 8; k++) 
     { 
     if (k != 7) 
     { 
      System.out.print(blocks[numberSchedule[i][k] - 1] + "\t"); 
     } 
     if (k == 7) 
     { 
      System.out.println(blocks[numberSchedule[i][k] - 1] + "\n"); 
     } 

     } 

    } 
    } 

}

來源

2014-09-20 user3813072

千萬不要這樣'k <8'，請使用長度屬性！ – Yoda 2014-09-20 22:02:57

請花一些時間來學習如何使用IDE的調試器。 – OldProgrammer 2014-09-20 22:04:39

@OldProgrammer - 在這個例子中，調試器不是必須的。順便說一句，我得到-1，告訴他初始化塊數組，但沒有發生其他事情。 – 2014-09-20 22:07:16