为什么在尝试输出数组时会出现异常错误？

Question

I have written a simple code that is supposed to output a 2D array. This is the code:

String month[];
int speedfines[][];

public int speedFines() {
    speedfines = new int[3][2];
    month = new String[2];

    month[0] = "JAN";
    month[1] = "FEB";
    month[2] = " MAR";

    speedfines[0][0] = 128;
    speedfines[0][1] = 135;
    speedfines[0][2] = 139;
    speedfines[1][0] = 155;
    speedfines[1][1] = 129;
    speedfines[1][2] = 175;
    speedfines[2][0] = 129;
    speedfines[2][1] = 130;
    speedfines[2][2] = 185;
    speedfines[3][0] = 195;
    speedfines[3][1] = 155;
    speedfines[3][2] = 221;

    System.out.println(Arrays.toString(speedfines));

    return 0;
}

When I run this code it gives me java exception in thread error. I am using netbeans 12.0 and I do not have any errors in my code but when I run I get the exception error error Can someone explain to me what the java exception means and how to fix it if possible.

Answer 1

The problem is the sizes you defined for the arrays month and speedfines .

For example, you defined size 2 to month and tryed to put 3 elements into it. To your code work properly, change the arrays definitions to:

speedfines = new int [4][3];
month = new String [3];

 -------------------
|      |      |     |     ⇒    Size = 3  /  month = new String [3]
 -------------------
   ↑       ↑     ↑
   0       1     2

Answer 2

Your month array should be:

month = new String[3];

When you set it to new String[2] , you are allowing 2 items to be in the array.

Since you set 3 items in the array:

month[0] = "JAN";
month[1] = "FEB";
month[2] = "MAR";

It raises the ArrayIndexOutOfBoundsException , because at this point index 2 does not exist.

Furthermore, your arrays are defined outside the function . Move them inside the function.

The code should be:

public int speedFines() {
    int speedfines[][] = new int[3][2];
    String month[] = new String[3];

    month[0] = "JAN";
    month[1] = "FEB";
    month[2] = "MAR";

    speedfines[0][0] = 128;
    speedfines[0][1] = 135;
    speedfines[0][2] = 139;
    speedfines[1][0] = 155;
    speedfines[1][1] = 129;
    speedfines[1][2] = 175;
    speedfines[2][0] = 129;
    speedfines[2][1] = 130;
    speedfines[2][2] = 185;
    speedfines[3][0] = 195;
    speedfines[3][1] = 155;
    speedfines[3][2] = 221;

    System.out.println(Arrays.toString(speedfines));

    return 0;
}

Answer 3

you save 12 items in array 2dimention so you need to do this speedfines = new int [4][3]; I think the exception name is ArrayIndexOutOfBounds that show when you put a size of array and give it items bigger than her size