## Thursday, 25 August 2016

### Chapter 8 Exercise 2, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

*8.2 (Sum the major diagonal in a matrix) Write a method that sums all the numbers in the major diagonal in an n * n matrix of double values using the following header: public static double sumMajorDiagonal(double[][] m) Write a test program that reads a 4-by-4 matrix and displays the sum of all its elements on the major diagonal. Here is a sample run: Enter a 4-by-4 matrix row by row: 1 2 3 4.0 5 6.5 7 8 9 10 11 12 13 14 15 16 Sum of the elements in the major diagonal is 34.5

import java.util.Scanner;

public class ProgramingEx8_2 {

public static void main(String[] args) {

double[][] matrix = new double[4][4];

java.util.Scanner input = new Scanner(System.in);
System.out.println("Enter a 4-by-4 matrix row by row: ");
for (int row = 0; row < matrix.length; row++) {
for (int column = 0; column < matrix[row].length; column++) {
matrix[row][column] = input.nextDouble();
}
}

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

}

public static double sumMajorDiagonal(double[][] m) {

double sum = 0;
for (int row = 0; row < m.length; row++) {
sum += m[row][row];
}
return sum;
}

}