如何初始化二维数组？

Question

I'm having trouble initializing an array. When I try to draw the Array I'm getting a NullPointerException .

I need to access the class where I've declared the array from another class, that's why it's static .

Here's my code:

static int[][] DayOfTheMonth = new int[3][10];


public static void ArrayValue() {
    for (int column = 0; DayOfTheMonth.length < 4; column++) {
        for (int row = 10; DayOfTheMonth[column].length < 10; row++) {
            if (DaysofTheMonth <= Tag.MaximumDaysOfAMonth()) {

                DayOfTheMonth.[column][row] = Date.getDate() + DaysofTheMonth;
                DaysofTheMonth++;

            } else if (DaysofTheMonth > Tag.MaxDay()) {
                DaysofTheMonth = 1;

                if (Month != 12)
                    Month++;
                else {
                    Month = 0;
                    Year++;

                }
            }
        }
    }
}

Another problem is that, when I try to access the method trough my main class, it says:

Exception in thread "Main" java.lang.ArrayIndexOutOfBoundsException: 3

Answer 1

ArrayIndexOutOfBoundsException states you are trying to access an Element from and Index that does not exists so,

In this line:

for (int column = 0;  DayOfTheMonth.length < 4; column++)

You have specified to go For Loop to go infinite because the length will always be less than 4 so you need to have column in condition like

for (int column = 0;  column < DayOfTheMonth.length; column++)

So Make it loop until 3, as it will start from 0 and go up to 3.

And 1 more thing for your clarity the 1st Thing is Row and Second is column, so you have 3 rows and 10 columns although its just related to naming-problem but you should be clear about it.

Answer 2

This is 2 questions. I can't answer the first because you don't say where the exception happens, and I don't know what you mean by "draw" the array.

For the second, your problem is here (and in similar places):

for (int column = 0; DayOfTheMonth.length < 4; column++) 

DayOfTheMonth.length will always evaluate to 3, so column will keep increasing. What you probably want is

for (int column = 0; column < DayOfTheMonth.length; column++) 

I make no claims as to whether this is the only problem.