java API 在包java.util中有一个GregorianCalendar类，使用它可以得到一年内某个月的日历.zip

import javax.swing.JOptionPane; public class Exercise6_6 { static String output = ""; /** Main method */ public static void main(String[] args) { // Prompt the user to enter year String yearString = JOptionPane.showInputDialog(null, "Enter full year (i.e. 2001):", "Example 4.6 Input", JOptionPane.QUESTION_MESSAGE); // Convert string into integer int year = Integer.parseInt(yearString); // Prompt the user to enter month String monthString = JOptionPane.showInputDialog(null, "Enter month in number between 1 and 12:", "Example 4.6 Input", JOptionPane.QUESTION_MESSAGE); // Convert string into integer int month = Integer.parseInt(monthString); // Print calendar for the month of the year printMonth(year, month); JOptionPane.showMessageDialog(null, output); System.exit(0); } /** Print the calendar for a month in a year */ static void printMonth(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 numOfDaysInMonth = getNumOfDaysInMonth(year, month); // Print headings printMonthTitle(year, month); // Print body printMonthBody(startDay, numOfDaysInMonth); } /** 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; long totalNumOfDays = getTotalNumOfDays(year, month); // Return the start day return (int)((totalNumOfDays + startDay1800) % 7); } /** Get the total number of days since Jan 1, 1800 */ static long getTotalNumOfDays(int year, int month) { long 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 + getNumOfDaysInMonth(year, i); return total; } /** Get the number of days in a month */ static int getNumOfDaysInMonth(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) if (isLeapYear(year)) return 29; else return 28; return 0; // If month is incorrect. } /** Determine if it is a leap year */ static boolean isLeapYear(int year) { if ((year % 400 == 0) || ((year % 4 == 0) && (year % 100 != 0))) return true; return false; } /** Print month body */ static void printMonthBody(int startDay, int numOfDaysInMonth) { // Pad space before the first day of the month int i = 0; for (i = 0; i < startDay; i++) output += " "; for (i = 1; i <= numOfDaysInMonth; i++) { if (i < 10) output += " " + i; else output += " " + i; if ((i + startDay) % 7 == 0) output += "\n"; } output += "\n"; } /** Print the month title, i.e. May, 1999 */ static void printMonthTitle(int year, int month) { output += " " + getMonthName(month) + ", " + year + "\n"; output += "-----------------------------\n"; output += " Sun Mon Tue Wed Thu Fri Sat\n"; } /** 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; } }