HW7.2

 import java.util.Scanner;

 public class Solution
 {
     public static void main(String[] args)
     {
         Scanner input = new Scanner(System.in);
         int[][] matrix = new int[4][4];
         System.out.println("Enter a 4-by-4 matrix row by row: ");
         for(int i = 0; i < 4; i++)
             for(int j = 0; j < 4; j++)
                 matrix[i][j] = input.nextInt();

         input.close();

         System.out.println("Sum of the elements in the major diagonal is " + sumMajorDiagonal(matrix));
     }

     public static int sumMajorDiagonal(int[][] m)
     {
         int sum = 0;
         for(int i = 0; i < 4; i++)
             sum += m[i][i];
         return sum;
     }
 }