Java——当用户输入日期字符串时显示一年中的某一天

Question

因此，该程序将用户输入视为格式为“m/d/yyyy”或“mm/dd/yyyy”的字符串。然后它将月份显示为单词(例如，月份 1 变为“January”)。我需要做的最后一件事是使用 GregorianCalendar 类来确定日期在一年中的序数位置。我真的不知道该怎么做。任何帮助将不胜感激。

import javax.swing.*;
import java.text.*;
import java.util.*;

public class ConvertDate {

   public static void main(String[] args) {


      String date = "";
      String[] monthName = 
         {"January", "February", "March", "April", 
            "May", "June", "July", "August", 
            "September", "October", "November", "December"};

      Integer[] daysInMonth = {29, 30, 31};

      int mm = 0;
      int dd = 0;
      int yy = 0;   

      String month = "";
      String day = "";
      String year = "";

      int maxDay = 0;


      while(mm < 1 || mm > 12 || dd < 1 || dd > maxDay) {            


         date = JOptionPane.showInputDialog(null, "Please, enter a date in the format MM/DD/YYYY.");

         String[] partsOfTheDate = date.split("/");

         mm = Integer.parseInt(partsOfTheDate[0]); 
         dd = Integer.parseInt(partsOfTheDate[1]);
         yy = Integer.parseInt(partsOfTheDate[2]);

         switch (mm) {
            case 1:  maxDay = daysInMonth[2]; // Jan
               break;
            case 2:  maxDay = daysInMonth[0]; // Feb 
               break;
            case 3:  maxDay = daysInMonth[2]; // Mar
               break;
            case 4:  maxDay = daysInMonth[1]; // Apr
               break;
            case 5:  maxDay = daysInMonth[2]; // May
               break;
            case 6:  maxDay = daysInMonth[1]; // Jun
               break;
            case 7:  maxDay = daysInMonth[2]; // Jul
               break;
            case 8:  maxDay = daysInMonth[2]; // Aug
               break;
            case 9:  maxDay = daysInMonth[1]; // Sep
               break;
            case 10: maxDay = daysInMonth[2]; // Oct
               break;
            case 11: maxDay = daysInMonth[1]; // Nov
               break;
            case 12: maxDay = daysInMonth[2]; // Dec
               break;
            default: maxDay = 0;
               break;
         }

         if((mm < 1 || mm > 12) || (dd < 1 || dd > maxDay)) {
            System.out.println("You entered " + date + ";\nyou did not include a valid month, day, or both.");
         }   
         else if((mm > 0 && mm < 13) && (dd > 0 && dd <= maxDay)) {
            System.out.println("You entered " + date + ";\nthat can also be expressed as " + monthName[mm - 1] + " " + dd + ", " + yy + ".");   
         }     

         GregorianCalendar greg = new GregorianCalendar();  
         greg.setTime(date);  
         greg.get(greg.DAY_OF_YEAR); 

      }   

   }  

}

Answer 1

使用SimpleDateFormat将String解析为Date，然后将Date设置为Calendar > 并获取 day_of_year

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