问题描述

我正在处理一项 Java 作业，它涉及在用户指定月份和年份后打印日历.我不能使用 Calendar 或 GregorianCalendar 类.我的问题是日历在星期六的第一天没有正确打印月份.我已经查看了我的代码大约一个小时，但我不确定出了什么问题.我正在使用 Zeller's Congruence 来查找该月的第一天，用h"表示.

I'm working on a Java assignment and it involves printing a calendar after the user specifies a month and a year. I cannot use the Calendar or GregorianCalendar classes. My problem is that the calendar does not correctly print months with their first day on a Saturday. I've looked at my code for about an hour now, and I'm not sure what went wrong. I'm using Zeller's Congruence to find the first day of the month, which is represented by "h".

例如，2008 年 3 月的日历(错误地)如下所示:

For example, the calendar on March 2008 (incorrectly) looks like this:

     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 

这是我的代码:

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);
    }    
}

推荐答案

从星期六开始的每个月.这意味着问题可能出在这一行 -

Your code will have the same issue for every month that starts with a Saturday. This means that the problem is probably in this line -

for (int i = 0; i < h - 1; i++)
  System.out.print("   ");

在这里将 h 设为 7 而不是 0 将为您解决此问题.您可以在此处修复该问题，或者您可能需要从 1 到 7 而不是 0 到 6 开始 h 并进行其他所需的更改.

Having h as 7 instead of 0 here will fix it for you. You can either fix that here or you may need to start h from 1 to 7 instead of 0 to 6 and make other required changes of course.

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