HourglassSum.java

public class HourglassSum {
    static int maxHourglassSum(int[][] mat) {
        int rows = mat.length;
        int cols = mat[0].length;
        int maxSum = Integer.MIN_VALUE;

        for (int i = 0; i <= rows - 3; i++) {
            for (int j = 0; j <= cols - 3; j++) {
                int sum = mat[i][j] + mat[i][j + 1] + mat[i][j + 2]
                         + mat[i + 1][j + 1]
                         + mat[i + 2][j] + mat[i + 2][j + 1] + mat[i + 2][j + 2];
                maxSum = Math.max(maxSum, sum);
            }
        }
        return maxSum;
    }

    public static void main(String[] args) {
        int[][] mat = {
            {1, 1, 1, 0, 0},
            {0, 1, 0, 0, 0},
            {1, 1, 1, 0, 0},
            {0, 9, 2, -4, -4},
            {0, 0, 0, -2, 0}
        };
        System.out.println("Maximum Hourglass Sum: " + maxHourglassSum(mat));
    }
}