HW7.1

 import java.util.Scanner;

 public class Solution
 {
     public static void main(String[] args)
     {
         Scanner input = new Scanner(System.in);
         double[][] matrix = new double[4][4];
         System.out.print("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.nextDouble();

         input.close();
         System.out.println("Sum of the matrix is " + sumMatrix(matrix));
     }

     public static double sumMatrix(double[][] m)
     {
         double sum = 0;
         for(double[] i: m)
             for(double j: i)
                 sum += j;
         return sum;
     }
 }