How to put values taken from a text file inside a matrix

Question

I can't put numbers taken froma text file inside a matrix.

The text file is this:

4
0 24 12 52
24 0 16 23
12 16 0 18
52 23 18 0

I tried this:

public class Siti {

    public static void main(String[] args) throws FileNotFoundException, IOException {
        BufferedReader reader = new BufferedReader(new FileReader("C://Users//dbruschi//Java-projects//NodiTelefonici//nodi.txt"));

        String line = null;

        ArrayList<Integer> numbers = new ArrayList<>();

        while ((line = reader.readLine()) != null) {
            StringTokenizer token = new StringTokenizer(line);
            while (token.hasMoreTokens()) {
                int num = Integer.parseInt(token.nextToken());
                numbers.add(num);
            }
        }
        System.out.println(numbers);

        int dimension = numbers.get(0);


        System.out.println("The dimension is: " + dimension);

        ArrayList<ArrayList<Integer>> matrix = new ArrayList<ArrayList<Integer>>();

        for(int j = 0; j < dimension; j++) {
            ArrayList<Integer> matrixRow = new ArrayList<Integer>();
            for (int i = 1; i < dimension+1; i++) {
                int elem = numbers.get(i);
                matrixRow.add(elem);
            }
            matrix.add(matrixRow);
        }
        System.out.println(matrix);
     }
}

And of course the output is this:

[[0, 24, 12, 52], [0, 24, 12, 52], [0, 24, 12, 52], [0, 24, 12, 52]]

I tried without arraylist but I want to manage rows and columns and so i think that arraylist is the best way