Multidimensional array calendar, how to fix simple issues

Question

I am trying to fix my Calendar (Month-March):

Mon Tue Wed Thu Fri Sat Sun 
1   2   3   4   5   6   7   
8   9   10  11  12  13  14  
15  16  17  18  19  20  21  
22  23  24  25  26  27  28  
29  30  31  0   0   0   0   
32  0   0   0   0   0   0   

1) The first problem is that I can't stop counting after 31, as you can see I have 0 0 0 0 0 but in this place I would like to have empty space.

2) Second problem is that March is starting from Thursday, not from Monday, how to start counting days from Thursday?. This is my code:

public class MyPoorCalendar{
    public static void main(String[] args) {
        int firstday = 1;
        int mycalendar[][] = new int[6][7];
        String nameOfTheWeeks = "Mon\t" + "Tue\t" + "Wed\t" + "Thu\t" + "Fri\t" + "Sat\t" + "Sun\t";
        System.out.println(nameOfTheWeeks);

        //initializing
        for (int i = 0; i < 6; i++) {
            for (int j = 0; j < 7; j++) {
                mycalendar[i][j] = firstday++;
                if (firstday > 31) {
                    break;
                }
            }
        }
        //printing
        for (int i = 0; i < 6; i++) {
            for (int j = 0; j < 7; j++) {
                System.out.print(mycalendar[i][j] + "\t");
                if (j == 6) {
                    System.out.println();
                }
            }
        }
    }
}

Answer 1

Just print a blank space when mycalendar[i][j] == 0

 System.out.print((mycalendar[i][j] == 0 ? " " : mycalendar[i][j]) + "\t");

When setting the values you should break out of the outer most for loop, currently you only break out of the inner most loop so do this instead

   for (int i = 0; i < 6; i++) {
        for (int j = 0; j < 7; j++) {
            mycalendar[i][j] = firstday++;
        }
        if (firstday > 31) {
                break;
        }
    }

Lastly if you want to start at a different location in the calendar then you could place a counter that, when it equals 0 you start your days. For example if you wanted to start on Thursday you could do something like this

   int dayToStartOn = 4; //Thursday
   for (int i = 0; i < 6; i++) {
        for (int j = 0; j < 7; j++) {
            mycalendar[i][j] = dayToStartOn-- > 0 ? 0 : firstday++;
        }
        if (firstday > 31) {
                break;
        }
    }

Answer 2

You can do this (explanation in code):

// store the length of the month and the first day of month's weekday number
int lengthOfMonth = LocalDate.now().lengthOfMonth();
int firstDayOfMonthsWeekDay = LocalDate.now().withDayOfMonth(1).getDayOfWeek().getValue();

// use a labeled break statement to terminate the outer for loop when we reach the end of the month
month:
for (int i = 0; i < 6; i++) {
    for (int j = 0; j < 7; j++) {
        if(--firstDayOfMonthsWeekDay > 0){ // fixing first day of month's weekday to start counting from tuesday for example
            continue;
        }

        mycalendar[i][j] = firstday++;
        if (firstday > lengthOfMonth) {
            break month;                   // the execution will continue after the outer loop
        }
    }
}

for (int i = 0; i < 6; i++) {
    for (int j = 0; j < 7; j++) {
        System.out.print((mycalendar[i][j] == 0 ? " " : mycalendar[i][j]) + "\t");  // replace 0's in the array with spaces
        if (j == 6) {
            System.out.println();
        }
    }
}

Output:

Mon Tue Wed Thu Fri Sat Sun 
            1   2   3   4   
5   6   7   8   9   10  11  
12  13  14  15  16  17  18  
19  20  21  22  23  24  25  
26  27  28  29  30  31   

More information about labeled break here . And about the java.time api here .