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SumElementsByColumn.java

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/*

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

Write a test program that reads a 3-by-4 matrix and displays the sum of each

column. Here is a sample run:

Enter a 3-by-4 matrix row by row:

1.5 2 3 4

5.5 6 7 8

9.5 1 3 1

Sum of the elements at column 0 is 16.5

Sum of the elements at column 1 is 9.0

Sum of the elements at column 2 is 13.0

Sum of the elements at column 3 is 13.0 */

import java.util.Scanner;

public class Project8_1{

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

double sum = 0; //intialize sum variable

//For loop sums matrix per column index

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

sum += m[i][columnIndex];

}

return sum;

}

public static void main (String[] args){

Scanner input = new Scanner(System.in);

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

System.out.println("Enter a 3-by-4 matrix row by row:");

//Initialize 3x4 matrix based on user input

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

for(int column = 0; column < m[row].length; column++){

m[row][column] = input.nextDouble();

}

}

//Display sum per column index

for (int column = 0; column < m[0].length; column++) {

System.out.println("Sum of the elements at column " + column + " is " + sumColumn(m, column));

}

}

}