calculate & compare slash diagonals in square matrix

class alaxon {
    public static boolean calc_slash_diagonal(int[][] sqr) { // calc by right and down
        // # right through the first row
        int i=0;
        int ret = calc_slash_diagonal(sqr, 0, i, 0);
        i++;
        while (i <= sqr.length-1) {
            if (ret == calc_slash_diagonal(sqr, 0, i, 0))
                i++;
            else
                return false;
        }

        // # down through the last column from the second line
            int j=1;
        i = sqr.length-1;
        while (j <= sqr.length-1) {
            if (ret == calc_slash_diagonal(sqr, j, i, 0))
                j++;
            else
                return false;
        }
        return true;
    }

    public static int calc_slash_diagonal(int[][] sqr, int x, int y, int sum) {
        if ((x > sqr.length-1) || (x < 0) || (y > sqr.length-1 || (y < 0))) { // end of diagonal
            return sum;
        }
        return calc_slash_diagonal(sqr, x+1, y-1, sum+sqr[x][y]);
    }

    public static void main(String[] args) {
        int[][] sqr = { {8, -3, 3, 1, 0},
                    {11, 4, 3, 2, 8},
                {1, 6, 3, 0, 8},
                {-2, 2, 0, 7, 3},
                {1, 0, -7, 5, 8} };

        int[][] sqr2 = { {8, -3, 3, 1, 0},
                    {11, 4, 3, 2, 8},
                {1, 6, 3, 0, 8},
                {-2, 2, 0, 7, 3},
                {1, 0, -7, 5, 9} };


         int[][] sqr3 = { {8, 8, 8, 8, 8},
                                {0, 0, 0, 0, 8},
                                {0, 0, 0, 0, 8},
                                {0, 0, 0, 0, 7},
                                {0, 0, 0, 1, 8} };

                System.out.println(calc_slash_diagonal(sqr));
                System.out.println(calc_slash_diagonal(sqr2));
                System.out.println(calc_slash_diagonal(sqr3));

    }
}