java 计算时间段

import javax.swing.JOptionPane;public class PrintCalendar {  /** Main method */  public static void main(String[] args) {    // Prompt the user to enter year    String yearString = JOptionPane.showInputDialog(      "Enter full year (e.g., 2001):");    // Convert string into integer    int year = Integer.parseInt(yearString);    // Prompt the user to enter month    String monthString = JOptionPane.showInputDialog(      "Enter month as number between 1 and 12:");    // Convert string into integer    int month = Integer.parseInt(monthString);    // Print calendar for the month of the year    printMonth(year, month);  }  /** Print the calendar for a month in a year */  static void printMonth(int year, int month) {    // Print the headings of the calendar    printMonthTitle(year, month);    // Print the body of the calendar    printMonthBody(year, month);  }  /** Print the month title, e.g., May, 1999 */  static void printMonthTitle(int year, int month) {    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 */  public 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;  }  /** Print month body */  public 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 */  public 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 Jan 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 */  public 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 */  public static boolean isLeapYear(int year) {    return year % 400 == 0 || (year % 4 == 0 && year % 100 != 0);  }}