Question

Can someone explain this code with comments I am supposed to dispay an array an add each columns and add each row

An application uses a two-dimensional array declared as follows: int[][] days = new int[29][5]; a. Write code that sums each row in the array and displays the results. b. Write code that sums each column in the array and displays the results.

class TwoDimensionalArrayDemo
{
  public static void main( String[] arg ) {
      
  int[][] days = new int[29][5];

 for (int i = 0; i < days.length; i++) {
      for (int j = 0; j < days[i].length; j++) {
          days[i][j] = i + j;
      }
  }

  
  for (int[] a : days) {
      for (int i : a) {
          System.out.print(i + "\t");
      }
      System.out.println("\n");
  } 
  System.out.println("column totals"); 
   int totalRow = 0;
  for( int col = 0; col < 5; col++)
  {
          totalRow = 0;
      for( int row = 0; row < 29; row++)
        totalRow = totalRow + days [row][col];
          System.out.println(totalRow);
  }
  System.out.println("row totals");
   int totalCol;
      for( int row = 0; row < 29; row++)
      {
       totalCol = 0;
    for( int col = 0; col < 5; col++)
           totalCol = totalCol + days [row] [col];
    System.out.println(totalCol);
}

}
}

Answer 1

// Defines a class TwoDimensionalArrayDemo for matrix implementation

public class TwoDimensionalArrayDemo

{

// main method definition

public static void main( String[] arg)

{

/*

* Creates an array of 29 X 5

* Number of rows is 29

* Number of columns is 5

* new keyword is used to dynamically allocate memory

*/

int[][] days = new int[29][5];

// Loops till number of rows (days.length will provide number of rows)

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

{

// Loops till number of columns

// (days[i].length will provide number of columns in ith row)

for (int j = 0; j < days[i].length; j++)

{

// Adds i and j value and stores it at ith row and jth column position

days[i][j] = i + j;

}// End of inner for loop (for column)

}// End of outer for loop (for row)

/*

* Enhanced for loop is used to access matrix

* Extract each row from the matrix and stores it in a

*/

for (int[] a : days)

{

// Each column value is extracted from array a

for (int i : a)

{

// Displays current cell value stored in i with tab space

System.out.print(i + "\t");

}// End of inner for loop

// Displays new line character to move to next line for next row

System.out.println("\n");

}// End of outer for loop

// Displays heading

System.out.println("column totals");

// To store column sum

int totalCol = 0;

// Loops till number of columns

for( int col = 0; col < 5; col++)

{

// Resets the total to 0 for each column sum

totalCol = 0;

// Loops till number of rows

for( int row = 0; row < 29; row++)

// Calculates total by moving row index and keeping column constant

totalCol = totalCol + days [row][col];

// Displays current column total

System.out.println("Column " + (col + 1) + " total = " + totalCol);

}// End of outer for loop

// Displays heading

System.out.println("row totals");

// To store row sum

int totalRow = 0;

// Loops till number of rows

for( int row = 0; row < 29; row++)

{

// Resets the total to 0 for each row sum

totalRow = 0;

// Loops till number of columns

for( int col = 0; col < 5; col++)

// Calculates total by moving column index and keeping row constant

totalRow = totalRow + days [row] [col];

// Displays current column total

System.out.println("Row " + (row + 1) + " total = " + totalRow);

}// End of outer for loop

}// End of main method

}// End of class

Sample Output:

0 1 2 3 4

1 2 3 4 5

2 3 4 5 6

3 4 5 6 7

4 5 6 7 8

5 6 7 8 9

6 7 8 9 10

7 8 9 10 11

8 9 10 11 12

9 10 11 12 13

10 11 12 13 14

11 12 13 14 15

12 13 14 15 16

13 14 15 16 17

14 15 16 17 18

15 16 17 18 19

16 17 18 19 20

17 18 19 20 21

18 19 20 21 22

19 20 21 22 23

20 21 22 23 24

21 22 23 24 25

22 23 24 25 26

23 24 25 26 27

24 25 26 27 28

25 26 27 28 29

26 27 28 29 30

27 28 29 30 31

28 29 30 31 32

column totals

Column 1 total = 406

Column 2 total = 435

Column 3 total = 464

Column 4 total = 493

Column 5 total = 522

row totals

Row 1 total = 10

Row 2 total = 15

Row 3 total = 20

Row 4 total = 25

Row 5 total = 30

Row 6 total = 35

Row 7 total = 40

Row 8 total = 45

Row 9 total = 50

Row 10 total = 55

Row 11 total = 60

Row 12 total = 65

Row 13 total = 70

Row 14 total = 75

Row 15 total = 80

Row 16 total = 85

Row 17 total = 90

Row 18 total = 95

Row 19 total = 100

Row 20 total = 105

Row 21 total = 110

Row 22 total = 115

Row 23 total = 120

Row 24 total = 125

Row 25 total = 130

Row 26 total = 135

Row 27 total = 140

Row 28 total = 145

Row 29 total = 150