打印出一周的在Java中日

Question

我试着让我的程序打印出来使用，我要编写和申报功能的任何给定日期的当天，虽然每月的月初日期似乎没有程序打印写日。 dayOfWeek函数w中的方程式给我们计算了一天，尽管对于要使用的'floor'代码，我必须根据我不太确定的原因创建另一个'private static'函数，因为为什么会是伟大的以及为什么我的程序为什么没有在特定日期返回正确的日期。

这里是我的代码，任何帮助将不胜感激:)

import java.util.Scanner; 
import javax.swing.JOptionPane; 

public class DayOfTheWeek { 

    public static final int SEPTEMBER_APRIL_JUNE_NOVEMBER_DAYS = 30; 
    public static final int REST_OF_YEAR_DAYS = 31; 
    public static final int LEAP_YEAR_FEB = 29; 
    public static final int NORMAL_FEB = 28; 
    public static final int MONTHS = 12; 

    public static void main(String[] args) { 
     try 
     { 
      String input = JOptionPane.showInputDialog("Enter date (day/month/year):"); 
      Scanner scanner = new Scanner(input); 
      scanner.useDelimiter("/"); 
      int day = scanner.nextInt(); 
      int month = scanner.nextInt(); 
      int year = scanner.nextInt(); 
      scanner.close(); 

      String numberEnding = numberEnding (day); 
      String dayEnding = day + numberEnding; 
      String monthName = monthName (month); 
      String dayName = dayOfTheWeek (day, month, year); 

      if (validDate(day, month, year)) 
      { 
       JOptionPane.showMessageDialog(null, dayName + " " + dayEnding + " " + monthName 
         + " " + year + " is a valid date."); 
      } 
      else 
      { 
       JOptionPane.showMessageDialog(null, "" + dayEnding + " " + monthName 
         + " " + year + " is not a valid date.", 
         "Error", JOptionPane.ERROR_MESSAGE); 
      } 
     } 
     catch (NullPointerException exception) 
     { 
     } 
     catch (java.util.NoSuchElementException exception) 
     { 
      JOptionPane.showMessageDialog(null, "No number entered. \nPlease restart and try again.", 
        "Error", JOptionPane.ERROR_MESSAGE); 
     }  
    } 
    public static boolean validDate(int day, int month, int year) { 
     return ((year >= 0) && (month >= 1) && (month <= MONTHS) && 
       (day >= 1) && (day <= daysInMonth(month, year))); 
    } 
    public static int daysInMonth(int month, int year) { 
     int monthDays; 
     switch (month) 
     { 
     case 2: 
      monthDays = isLeapYear(year) ? LEAP_YEAR_FEB : NORMAL_FEB;            
      break; 
     case 4: 
     case 6: 
     case 9: 
     case 11: 
      monthDays = SEPTEMBER_APRIL_JUNE_NOVEMBER_DAYS; 
      break; 
     default: 
      monthDays = REST_OF_YEAR_DAYS; 
     } 
     return monthDays; 
    } 
    public static boolean isLeapYear(int year) { 
     return (((year%4 == 0) && (year%100 != 0)) || (year%400 == 0)); 
    } 
    public static String numberEnding(int day) { 
     String dayEnding = ""; 
     int remainder = day%10; 
     if (day >= 10 && day <= 20) 
     { 
      dayEnding = "th"; 
     } 
     else 
     { 
      switch (remainder) 
      { 
      case 1: 
       dayEnding = "st"; 
       break; 
      case 2: 
       dayEnding = "nd"; 
       break; 
      case 3: 
       dayEnding = "rd"; 
       break; 
      default: 
       dayEnding = "th"; 
       break; 
      } 
     } 
     return dayEnding; 
    } 
    public static String monthName(int month) { 
     String monthName = ""; 
     switch (month) 
     { 
     case 1: 
      monthName = "January"; 
      break; 
     case 2: 
      monthName = "February"; 
      break; 
     case 3: 
      monthName = "March"; 
      break; 
     case 4: 
      monthName = "April"; 
      break; 
     case 5: 
      monthName = "May"; 
      break; 
     case 6: 
      monthName = "June"; 
      break; 
     case 7: 
      monthName = "July"; 
      break; 
     case 8: 
      monthName = "August"; 
      break; 
     case 9: 
      monthName = "September"; 
      break; 
     case 10: 
      monthName = "October"; 
      break; 
     case 11: 
      monthName = "November"; 
      break; 
     case 12: 
      monthName = "December"; 
      break; 
     default: 
     } 
     return monthName; 
    } 
    public static String dayOfTheWeek (int day, int month, int year){ 
     String dayName = ""; 
     int Y; 
     if (month == 1 || month == 2) 
     { 
      Y = (year-1); 
     } 
     else 
     { 
      Y = (year); 
     } 
     int y = Y%100; 
     int c = Y/100; 
     int w = (day + floor(2.6 * (((month+9) % 12)+ 1) -0.2) 
       + y + floor(y/4) + floor(c/4) - (2*c)); 
     w = (w%7); 
     if (w < 0) 
     { 
      w += 7; 
     } 
     switch (w) 
     { 
     case 0: 
      dayName = "Sunday"; 
      break; 
     case 1: 
      dayName = "Monday"; 
      break; 
     case 2: 
      dayName = "Tuesday"; 
      break; 
     case 3: 
      dayName = "Wednesday"; 
      break; 
     case 4: 
      dayName = "Thursday"; 
      break; 
     case 5: 
      dayName = "Friday"; 
      break; 
     case 6: 
      dayName = "Saturday"; 
      break; 
     } 
     return dayName; 
    } 
    private static int floor(double d) { 
     return 0; 
    } 
} 

Answer 1

我相信你需要使用Math.floor()方法。直接使用(int)

(day + Math.floor(2.6 * (((month+9) % 12)+ 1) -0.2) 
       + y + Math.floor(y/4) + Math.floor(c/4) - (2*c)); 

您也可以施放公式：代替你的地板的方法简单地调用这个

int w = (int) (day + 2.6 * ((month+9) % 12 + 1) - 0.2 + y + (y/4) + (c/4) - (2*c)); 

然而，在你的情况我觉得值会不恰当地使用铸造四舍五入，所以你应该使用floor方法。

如果您想在地板上和铸造这里之间的区别一些额外的信息是，解决这一个计算器问题：Cast to int vs floor

Answer 2

我会使用Joda-Time库。

import org.joda.time.DateTime 

final DateTime date = new DateTime(); 
final int dayOfWeek = date.getDayOfWeek(); 

见乔达时间User Guide获取更多信息和例子..