NullPointException error when parsing string 1D array to int 2D array

Question

Background: I am writing a program that uses BufferedReader to store several lines of a text file into a String array.

Example of text file:

4 5

4 5 2 3 3

3 2 1 3 2

2 3 1 2 3

3 3 2 1 2

2 3 1 2 1

ArrayList of textfile lines:

["4 5"]["4 5 2 3 3"]["3 2 1 3 2"]["2 3 1 2 3"]["3 3 2 1 2"]["2 3 1 2 1"]

Need a 2D array like this:

[3][2]1[3][2]

[2][3]1[2][3]

[3][3]2[2]

[2][3]1[2]1

The first line(array element) essentially indicates the size of my array which I successfully created a new array using array.split(" "): [4][5]. The second line is used for a different method which was successful as well using array.split(" "). I'm having an issue with lines 3-6.

void allocatedUnits(){
    String au;
    start_alloRow = 2;                          //start row 2 of text file
    end_alloRow = start_alloRow + num_process;  //length is how many processes were indicated

    for (int i = start_alloRow; i < end_alloRow; i++){
        au = fileArray[i];                      //fileArray element i into String au (i=start-end)
        String[] array = au.split(" ");         //split String au "i" into array elements
        for (int j = 0; j <= array.length; j++){         //for element j 0-arraylength (0-num_resource)
            allocatedArray[i][j] = Integer.parseInt(array[j]);  //use alloArray[i] row for [j] element
            System.out.println(allocatedArray[i][j]); //print each element
        }

    }}

The error I get is NullPointerExcetion at the line of allocatedArray[i][j] = Integer.parseInt(array[j]);

I have printed the String[] array elements without the 2D array and it prints correctly, so I'm unsure if I'm creating the 2D array incorrectly.

Error screenshot

EDIT:// I now have an ArrayIndexOutOfBounds exception which I understand, but don't know how to fix it. This is my updated code with initialized array (which helped)

void allocatedUnits(){
    String au;
    start_alloRow = 2;                          //start row 2 of text file
    end_alloRow = start_alloRow + num_process;  //length is how many processes were indicated
    allocatedArray = new int[num_process][num_resource];

    for (int i = start_alloRow; i < end_alloRow; i++){
        int k = 0;
        au = fileArray[i];                      //fileArray element i into String au (i=start-end)
        String[] array = au.split(" ");         //split String au "i" into array elements
        for (int j = 0; j < array.length; j++){ //for element j 0-arraylength (0-num_resource)
            allocatedArray[k][j] = Integer.parseInt(array[j]);  //use alloArray[i] row for [j] element
            System.out.println(allocatedArray[k][j]); //print each element
            k++;
        }
    }
}

Answer 1

You need to fully initialize allocatedArray. To do that, you need to know two things:

1. How many subarrays you want it to have.
2. How big each subarray should be.

So in your case, you should first do:

allocatedArray = new int[end_alloRow - start_alloRow][];

then initialize the subarray like this:

au = fileArray[i];
String[] array = au.split(" ");
allocatedArray[i] = new int[array.length];

and finally set the values like this:

allocatedArray[i - start_alloRow][j] = Integer.parseInt(array[j]);