如何从Java用户输入中获取日期？

Question

我需要从用户指定的输入日期开始打印日历。但是，我不允许使用任何预定义的日期类。

目前，我可以打印月份和年份，但是我似乎无法弄清楚如何打印特定月份+年中该日期所在的日期。我是Java的新手，所以将不胜感激！

这里是所需输出的示例：

24/05/2020 is a Sunday and locates in the fourth week of May 2020

The calendar of May 2020 is:

MON TUE WED THU FRI SAT SUN 
                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

到目前为止是我的输出：

22/5/2020 is a null and located in May

Here is the calendar for May: 

         May 2020
-----------------------------
 Sun Mon Tue Wed Thu Fri Sat
                       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

这是到目前为止我尝试过的：

import java.util.Scanner;

public class PrintCalendar {

/** Main method */

public static void main(String[] args) {

// Prompt the user to enter year
Scanner scanner = new Scanner(System.in);



// Prompt the user to enter year
System.out.print("Enter year (e.g.1999): ");

int year = scanner.nextInt();



// Prompt the user to enter month
System.out.print("Enter month (1-12): ");

int month = scanner.nextInt();

System.out.println("Enter the day (1-7): ");

int theDay = scanner.nextInt();



// Print calendar for the month of the year
printMonth(year, month, theDay);

}



/** Print the calendar for a month in a year */

static void printMonth(int year, int month, int day) {

// Print the headings of the calendar
printMonthTitle(year, month, day);



// Print the body of the calendar
printMonthBody(year, month);

}



/** Print the month title, e.g., May, 1999 */

static void printMonthTitle(int year, int month, int day) {

System.out.println(day + "/"+  month + "/" + year + " is a " + getDayOfWeek(day) + " and located in " + getMonthName(month));

System.out.println();

System.out.println("Here is the calendar for " + getMonthName(month) + ": ");

System.out.println();


System.out.println("         " + getMonthName(month)

  + " " + year);

System.out.println("-----------------------------");

System.out.println(" Sun Mon Tue Wed Thu Fri Sat");

}



/** Get the English name for the month */

static String getMonthName(int month) {

String monthName = null;

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";

}



return monthName;

}



public static String getDayOfWeek(int day) {

  String dayName = null;

  switch (day) {

  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;

  case 6: dayName = "Friday"; break;

  case 7: dayName = "Saturday"; 

  }

  return dayName;

}


/** Print month body */

static void printMonthBody(int year, int month) {

// Get start day of the week for the first date in the month
int startDay = getStartDay(year, month);



// Get number of days in the month
int numberOfDaysInMonth = getNumberOfDaysInMonth(year, month);



// Pad space before the first day of the month
int i = 0;

for (i = 0; i < startDay; i++)

  System.out.print("    ");



for (i = 1; i <= numberOfDaysInMonth; i++) {

  if (i < 10)

    System.out.print("   " + i);

  else

    System.out.print("  " + i);



  if ((i + startDay) % 7 == 0)

    System.out.println();

}



System.out.println();

}



/** Get the start day of the first day in a month */

static int getStartDay(int year, int month) {

// Get total number of days since 1/1/1800
int startDay1800 = 3;

int totalNumberOfDays = getTotalNumberOfDays(year, month);



// Return the start day
return (totalNumberOfDays + startDay1800) % 7;

}



/** Get the total number of days since January 1, 1800 */

static int getTotalNumberOfDays(int year, int month) {

int total = 0;



// Get the total days from 1800 to year - 1
for (int i = 1800; i < year; i++)

if (isLeapYear(i))

  total = total + 366;

else

  total = total + 365;



// Add days from Jan to the month prior to the calendar month
for (int i = 1; i < month; i++)

  total = total + getNumberOfDaysInMonth(year, i);



return total;

}



/** Get the number of days in a month */

static int getNumberOfDaysInMonth(int year, int month) {

if (month == 1 || month == 3 || month == 5 || month == 7 ||

  month == 8 || month == 10 || month == 12)

  return 31;



if (month == 4 || month == 6 || month == 9 || month == 11)

  return 30;



if (month == 2) return isLeapYear(year) ? 29 : 28;



return 0; // If month is incorrect
}



/** Determine if it is a leap year */

static boolean isLeapYear(int year) {

return year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);

  }

}

Answer 1

要获得星期几，您可以使用getStartDay()函数，使用该函数将返回您每月的开始日期，我们可以执行(day + startDay) % 7这将为我们提供当前日期的一天。

这里您需要进行一些更改：

打印语句：

 System.out.println(day + "/" + month + "/" + year + " is a " + getDayOfWeek(day, year, month) + " and located in " + getMonthName(month));

您的功能：

 //pass year and month as well
    public static String getDayOfWeek(int day, int year, int month) {
      String dayName = null;
      //getting start day of month
      int startDay = getStartDay(year, month);//call function
      int days = (day + startDay) % 7;
      //if days will be 0 means start month from monday and leap year
      if (days == 0) {
       //add 1 to day 
       days = day + 1;
      } else {
       //use same days
       days = days;

      }
      switch (days) {

       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;

       case 6:
        dayName = "Friday";
        break;

       case 7:
        dayName = "Saturday";

      }

      return dayName;
    }

输出：