Java实现按年月打印日历功能【基于Calendar】

import java.text.ParseException;import java.text.SimpleDateFormat;import java.util.Calendar;import java.util.Date;public class CalendarBook {  public static void main(String[] args) throws ParseException {    CalendarBook cb = new CalendarBook();    cb.printWeekTitle();    cb.printCalendar(2018, 3);  }  public void printCalendar(int year, int month) throws ParseException {    String monthStr; // 格式化月份，因为要转成yyyyMMdd格式的    if (month < 10) {      monthStr = "0" + month;    } else {      monthStr = month + ""; // 数字跟字符串拼接转成字符串格式    }    String yearMonthStr = year + monthStr;    SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd");    Calendar calendarEnd = Calendar.getInstance();    Calendar calendarStart = Calendar.getInstance();    // 根据年份和月份得到输入月份有多少天    int monthDays = getMonthLastDay(year, month);    // 月初的date字符串    String dateStartStr = yearMonthStr + "01";    // 月末的date字符串    String dateEndStr = yearMonthStr + monthDays;    Date startDate = sdf.parse(dateStartStr);    Date endDate = sdf.parse(dateEndStr);    calendarStart.setTime(startDate);    calendarEnd.setTime(endDate);    // 得到输入月份有多少周    int weeks = calendarEnd.get(Calendar.WEEK_OF_MONTH);    // 得到当月第一天是星期几，这里周日为第一天，从1开始，周一则为2    int dayOfWeek = calendarStart.get(Calendar.DAY_OF_WEEK);    int day = 1;    // 当月的第一周做特殊处理，单独打印一行    for (int i = 1; i <= 7; i++) {      if (i >= dayOfWeek) {        System.out.print(" " + day + " ");        day++;      } else {        System.out.print("  ");      }    }    System.out.println();    // 开始打印从第二周开始的日期    for (int week = 1; week < weeks; week++) {      for (int i = 1; i <= 7; i++) {        if (day > monthDays) {          break;        }        if (day < 10) {          System.out.print(" " + day + " ");        } else {          System.out.print(day + " ");        }        day++;      }      System.out.println();    }  }  public int getMonthLastDay(int year, int month) {    int monthDay;    int[][] day = { { 0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 },        { 0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 } };    if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {      // 闰年      monthDay = day[1][month];    } else {      monthDay = day[0][month];    }    return monthDay;  }  public void printWeekTitle() {    System.out.println("日" + "   " + "一" + "   " + "二" + "   " + "三"        + "   " + "四" + "   " + "五" + "   " + "六");  }}