为什么会收到“ java.lang.ArrayIndexOutOfBoundsException：0”

Question

What is wrong here? I get an runtime error when I run the code in Netbeans saying "java.lang.ArrayIndexOutOfBoundsException: 0"

I found out it means something like "the value does not exist" - but that is what I am trying to do - to let the user define the values for the array size. Help, please.

public static void main(String[] args) {

    int row = 0;
    int colum = 0;

    //Declare 2d array
    int [][] matrix = new int [row][colum];
    //Create input for array size
    Scanner input = new Scanner(System.in);
    System.out.println("Enter " + matrix[row].length + " rows and " + matrix[colum].length + " colums: ");
    for (row = 0; row < matrix.length; row++) {
        for (colum = 0; colum < matrix[row].length ; colum++) {
            matrix[row][colum] = input.nextInt();
    //Input variables to array


    //Print the array
    for (row = 0; row < matrix.length; row++ ) {
        for (colum = 0; colum < matrix[row].length; colum++ ) {
            System.out.println(matrix[row][colum] + "");
        }

        System.out.println();
    }



        }
    }








    }


}

Answer 1

For your case

int [][] matrix = new int [0][0];

Means with no element , index starts from 0, where the size you specify starts from 1

Go for ArrayList if you want dynamic array

Answer 2

Two problems. You need to initialize row and column with non-zero values:

int row = 3;
int colum = 4;

You're not referencing the dimensions of the matrix correctly, you want:

System.out.println("Enter " + matrix.length + " rows and "
        + matrix[0].length + " colums: ");

There are a few more bad references further down. You could of course just use your row and column variables instead of getting the lengths from the matrix though.

Answer 3

您的数组有0个元素-您正在尝试访问第一个（索引为0）-超出范围。

Answer 4

You are creating an array of arrays that has size 0 in both dimensions:

int row = 0;
int colum = 0;

//Declare 2d array
int [][] matrix = new int [row][colum];

If you try to index this you will get an ArrayIndexOutOfBoundsException .

Set row and colum to something > 0.

Arrays in Java have a fixed size. Once you have created an array, you can't change the size of it. If you need to change the size at runtime, use a collection class (for example an ArrayList ) instead of an array.

Answer 5

int row = 0;
int colum = 0;
int [][] matrix = new int [row][colum];

The declared array has zero rows and zero columns. You can't store anything in it.

The exception occurs here:

matrix[row].length

with row=0 because it is the number of columns of the first row (arrays are zero based!) which doesn't exist.

Answer 6

Your problem is that you're setting row and column to 0, then you create a two-dimensional array of size 0 in both directions, and then this:

matrix[row].length

fails because there is no entry at index 0 - it would require the array to have at least size 1.