could you please tell me how to understand the question

import java.io.; import java.math.; import java.security.; import java.text.; import java.util.; import java.util.concurrent.; import java.util.regex.*;

class Result {

/*
 * Complete the 'diagonalDifference' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts 2D_INTEGER_ARRAY arr as parameter.
 */

public static int diagonalDifference(List<List<Integer>> arr) {
    int left =0;
    int right =0;
    int n = arr.size();
   for(int i = 0 ; i < n; i++) {
        left += arr.get(i).get(i);
        right += arr.get(i).get(n-1-i);

    }

    return Math.abs(left-right);

}

}

public class Solution { public static void main(String[] args) throws IOException { BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in)); BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

    int n = Integer.parseInt(bufferedReader.readLine().trim());

    List<List<Integer>> arr = new ArrayList<>();

    for (int i = 0; i < n; i++) {
        String[] arrRowTempItems = bufferedReader.readLine().replaceAll("\\s+$", "").split(" ");

        List<Integer> arrRowItems = new ArrayList<>();

        for (int j = 0; j < n; j++) {
            int arrItem = Integer.parseInt(arrRowTempItems[j]);
            arrRowItems.add(arrItem);
        }

        arr.add(arrRowItems);
    }

    int result = Result.diagonalDifference(arr);

    bufferedWriter.write(String.valueOf(result));
    bufferedWriter.newLine();

    bufferedReader.close();
    bufferedWriter.close();
}

}

Solution in C

public static int diagonalDifference(List<List<int>> arr)
    {
        int left = 0;
        int right = 0 ;
        int indexRight = arr.Count();
        
        
        for(int x=0; x < arr.Count(); x ++){
            indexRight --;
            left += arr[x][x];
            right += arr[x][indexRight];
        }
        
        if(left > right)
            return left - right;
        else
            return right - left;
    }

Solution in PHP

function diagonalDifference(array arraySize = count($arr);

    // primary & secondary sum vars
    `$primarySum = $`secondarySum = 0;

    // looping the array
    for (`$x = 0; $`x < `$arraySize; $`x++) {
        // incrementing primary sum 
        `$primarySum += $`arr[`$x][$`x];

        // incrementing secondary sum
        `$secondarySum += $`arr[`$x][$`arraySize - 1 - $x];
    }

    // return absolute diagonal
    return abs(`$primarySum - $`secondarySum);

};

Solution in js

function diagonalDifference(arr) {
    // Write your code here
    let leftToRight = 0
    let rightToLeft = 0
for(let i =0;i<arr.length ;i++){
    leftToRight +=arr[i][i]
    rightToLeft += arr[i][arr.length-1-i]
}
return  Math.abs(leftToRight-rightToLeft)
}