2D Array - DS HACKKERANK

 import java.io.*;

import java.math.*;

import java.security.*;

import java.text.*;

import java.util.*;

import java.util.concurrent.*;

import java.util.function.*;

import java.util.regex.*;

import java.util.stream.*;

import static java.util.stream.Collectors.joining;

import static java.util.stream.Collectors.toList;

class Result {

    /*

     * Complete the 'hourglass sum function below.

     *

     * The function is expected to return an INTEGER.

     * The function accepts 2D_INTEGER_ARRAY arr as a parameter.

     */

    

    //Time O(1) as we know every time we have to iterate the loop

//through value 4 as array size will be fixed as 6.

//Space O(N) as we are using ArrayList for storing of values and then

//find out the max value from it.

    public static int hourglassSum(int[][] arr) {

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

        int sum=0;

        for(int i=0;i<4;i++){

            for(int j=0;j<4;j++){

                sum=arr[i][j]+arr[i][j+1]+arr[i][j+2]+arr[i+1][j+1]+arr[i+2][j]+arr[i+2][j+1]+arr[i+2][j+2];

                aa.add(sum);

                sum=0;

            }

        }

        System.out.println(Collections.max(aa));

        return Collections.max(aa);

    }

}

public class Solution {

    public static void main(String[] args) throws IOException {

        int arr[][]=new int[6][6];

        Scanner sc=new Scanner(System.in);

        for(int i=0;i<6;i++){

            for(int j=0;j<6;j++){

                arr[i][j]=sc.nextInt();

            }

        }

       Result obj=new Result();

       obj.hourglassSum(arr);

    }

}