嵌套循环，如何制作日历

Question

Hello I am a beginner and I am getting very angry at this problem because I can't quite figure out. The question is to make a calendar using NESTED LOOPS, can anyone help me out? The calendar should somewhat look like the one below, dates should be corresponding to the day of week and should also look like how a calendar looks like (spaces, structure...)

      Su   M   T   W   Th   F  Sa 
                   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

All i know is how to make columns and rows filled with "x's".

public class sumfOddsInNumber
{
    public static void main(String[] args)
    {
        for (int r = 1; r <= 6; r++)
        {
            for(int c = 1; c <= 7; c++)
            {
                System.out.print("x");
            }
            System.out.println();
        }
    }
}

Answer 1

Seems like this is a homework problem, so I'm not going to give you the code, but you're heading in the right direction. First, I'd change

System.out.print("x");

to

System.out.print("  x"); //Add two spaces in front of the x

so you have space between the numbers. Next, to generate actual numbers instead of x's, put int dayOfMonth = 1; above the for loop. You'll then want to print out dayOfMonth instead of x's. The problem I leave to you is how to make the value of dayOfMonth increase each time.

Answer 2

This is not really a programming issue, it is a question of logic. If you would concentrate for about 4 minutes straight, you would have figured it out. But I guess nobody takes their time with homework anymore. This is how bad programmers are born, please learn to have more ambition than a can opener.

---

I've made you a small, stylish example, that does exactly what you're asking for.

Code isn't optimized. I just left it like I've thought it (yup, 4 minutes). Please take the time to review and improve this example. Everything is explained by comments.

/**
 * The parameters indicate where the month starts,
 * and where it ends.
 *
 * @author ggrec
 *
 */
public class Calendar 
{
    private static final String WEEKDAYS = "Su Mo Tu We Th Fr Sa";
    private static final String NEW_LINE = "\n";
    private static final String EMPTY_STRING = " ";
    private static final String TRIPLE_EMPTY_STRING = "   ";

    public static void main(final String[] args) 
    {
        final String calendarString = getFormattedCalendar(4, 6);

        System.out.println(calendarString);
    }

    private static String getFormattedCalendar(final int startDay, final int endDay)
    {
        // Create StringBuilder
        final StringBuilder calendar = new StringBuilder();

        // Append weekdays to string header
        calendar.append(WEEKDAYS).append(NEW_LINE);

        // This will keep track of days
        int day = 1;

        for (int i = 1; i <= 5; i++) // Week loop
        {
            for (int j = 1; j <= 7; j++) // Weekday loop
            {
                // If we are on the last week of the month,
                // and we've reached the endDay that we specified,
                // simply return the assembled string
                if (i == 5 && j == endDay + 1)
                    return calendar.toString();

                // These are the empty spaces for the beginning of
                // the first week
                if (i == 1 && j < startDay)
                {
                    // Just append empty space, then CONTINUE
                    // to next iteration (j++)
                    calendar.append(TRIPLE_EMPTY_STRING);
                    continue;
                }

                // Check if the day is a single or double digit
                if (day / 10 >= 1)
                    calendar.append(day++).append(EMPTY_STRING);
                else
                    // If this is the first week, then it means that
                    // we have single-digit days. Apply strings on each
                    // side of the day for proper spacing of digits
                    calendar.append(EMPTY_STRING).append(day++).append(EMPTY_STRING);
            }

            calendar.append(NEW_LINE);
        }

        return calendar.toString();
    }
}