Question

(Sum elements column by column) Write a method that returns the sum of all the elements in a specified column in a matrix using the following header: public staticdouble sumColumn( double[] [] m, int columnIndex) Write a test program that reads a 3- by- 4 matrix and displays the sum of each column.

Answer 1

import java.util.Random;

public class Main {

/**

* @param args the command line arguments

*/

public static void main(String[] args) {

Random rand = new Random();

double[][] matrix = new double[3][4];

for (int r = 0; r < matrix.length; r++) {

for (int c = 0; c < matrix[r].length; c++) {

matrix[r][c] = rand.nextDouble();

System.out.print(matrix[r][c] + " ");

}

System.out.println();

}

for (int i = 0; i < 4; i++) {

System.out.println("Sum of column " + i + " is " + sumColumn(matrix, i));

}

}

public static double sumColumn(double[][] m, int columnIndex) {

double sum = 0;

for (int i = 0; i < m.length; i++) {

sum += m[i][columnIndex];

}

return sum;

}

}