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

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.