public static int diagonalDifference(List<List<Integer>> matrix) {
    int primaryDiagonalSum = 0;
    int secondaryDiagonalSum = 0;
    int n = matrix.size();
    for (int i = 0; i < n; i++) {
        primaryDiagonalSum += matrix.get(i).get(i); // Left-to-right diagonal
        secondaryDiagonalSum += matrix.get(i).get(n - i - 1); // Right-to-left diagonal
    }
    return Math.abs(primaryDiagonalSum - secondaryDiagonalSum);
}