Exercise 7.1

import java.util.Scanner;

public class Exercise7_1 {
  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;
  }

  public static void main(String[] args) {
    double[][] matrix = new double[3][4];
    String[][] rows = new String[3][4];
    Scanner in = new Scanner(System.in);
    System.out.println("Enter a 3-by-4 matrix row by row:");
    rows[0] = in.nextLine().split(" ");
    rows[1] = in.nextLine().split(" ");
    rows[2] = in.nextLine().split(" ");
    for (int i = 0; i < rows.length; i++) {
      for (var j = 0; j < rows[i].length; j++) {
        matrix[i][j] = Double.parseDouble(rows[i][j]);
      }
    }
    for (int i = 0; i < 4; i++) {
      double sum = sumColumn(matrix, i);
      System.out.println("Sum of the elements at column " + i + " is " + sum);
    }
  }
}