public static int diagonalDifference(List> arr) { int n = arr.size(); /// tam de la matriz int diagnonalPrincipal = 0; int diagonalSecundaria = 0;

    for(int i = 0; i<n;i++){
        diagnonalPrincipal += arr.get(i).get(i);
        diagonalSecundaria += arr.get(i).get(n-1-i);
    }

    return Math.abs(diagnonalPrincipal - diagonalSecundaria);


}