Ich arbeite an einer Java-Aufgabe und es wird ein Kalender gedruckt, nachdem der Benutzer einen Monat und ein Jahr angegeben hat. Ich kann die Klassen Calendar oder GregorianCalendar nicht verwenden. Mein Problem ist, dass der Kalender Monate mit ihrem ersten Tag an einem Samstag nicht richtig druckt. Ich habe meinen Code jetzt ungefähr eine Stunde lang durchgesehen und bin mir nicht sicher, was schief gelaufen ist. Ich benutze Zellers Kongruenz, um den ersten Tag des Monats zu finden, der durch "h" dargestellt wird.

Der Kalender vom März 2008 sieht beispielsweise (fälschlicherweise) folgendermaßen aus:

     March 2008
Su Mo Tu We Th Fr 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 

Hier ist mein Code:

package calendar;

import java.util.Scanner;

public class Calendar
{
    private static int numDays = 0;
    private static int h = 0;
    public static boolean leap(int year)
    {
        if(((year % 4 == 0) && !(year % 100 == 0)) || (year % 400 == 0))
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    public static void firstDayOfYear(int year)
    {
        int month = 13;
        year--;
        h = (1 + (int)(((month + 1) * 26) / 10.0) + year + (int)(year / 4.0) + 6 * (int)(year / 100.0) + (int)(year / 400.0)) % 7;
        String dayName = "";
        switch(h)
        {
            case 0: dayName = "Saturday"; break;
            case 1: dayName = "Sunday"; break;
            case 2: dayName = "Monday"; break;
            case 3: dayName = "Tuesday"; break;
            case 4: dayName = "Wednesday"; break;
            case 5: dayName = "Thursday"; break;
            default: dayName = "Friday"; break;
        }
        System.out.println("The first day of the year is " + dayName);
    }
    public static void firstDayOfMonth(int month, int year)
    {
        if(month == 1 || month == 2)
        {
            month += 12;
            year--;
        }
        h = (1 + (int)(((month + 1) * 26) / 10.0) + year + (int)(year / 4.0) + 6 * (int)(year / 100.0) + (int)(year / 400.0)) % 7;
        String dayName = "";
        switch(h)
        {
            case 0: dayName = "Saturday"; break;
            case 1: dayName = "Sunday"; break;
            case 2: dayName = "Monday"; break;
            case 3: dayName = "Tuesday"; break;
            case 4: dayName = "Wednesday"; break;
            case 5: dayName = "Thursday"; break;
            default: dayName = "Friday"; break;
        }
        System.out.println("The first day of the month is " + dayName);
    }
    public static void numDaysInMonth(int month, int year)
    {
        int[] days = { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };

        if (month == 2 && leap(year)) days[month] = 29;
        numDays = days[month];
        System.out.println("The number of days in the month is " + numDays);
    }
    public static void printCal(int month, int year)
    {
        String[] monthNames = {"","January","February","March","April","May","June","July","August","September","October","November","December"};

        System.out.println("    " + monthNames[month] + " " + year);
        System.out.println("Su Mo Tu We Th Fr Sa");
        for (int i = 0; i < h - 1; i++)
            System.out.print("   ");
        for (int i = 1; i <= numDays; i++)
        {
            System.out.printf("%2d ", i);
            if (((i + h - 1) % 7 == 0) || (i == numDays)) System.out.println();
        }
    }
    public static void main(String[] args)
    {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter month (1-12): ");
        int month = input.nextInt();
        if(month < 1 || month > 12)
        {
            System.out.println("Invalid month. Valids inputs are 1-12.");
            System.exit(0);
        }
        System.out.print("Enter year: ");
        int year = input.nextInt();
        if(year < 1753)
        {
            System.out.println("Invalid year. Valid inputs are 1753 and beyond.");
            System.exit(0);
        }
        if(leap(year))
        {
            System.out.println(year + " is a leap year.");
        }
        else
        {
            System.out.println(year + " is NOT a leap year.");
        }
        firstDayOfYear(year);
        firstDayOfMonth(month, year);
        numDaysInMonth(month, year);
        printCal(month, year);
    }    
}