第四章：显示当月日期的小程序。

 1 package cha4;
 2 
 3 import java.text.DateFormatSymbols;
 4 import java.util.Calendar;
 5 import java.util.GregorianCalendar;
 6 
 7 public class CalendarTest {
 8 
 9     public static void main(String[] args) {
10         GregorianCalendar today = new GregorianCalendar(2014,10,30) ;
11         
12         int curMonth = today.get(Calendar.MONTH) ;
13         today.set(Calendar.DAY_OF_MONTH, 1);
14         
15         int weekday = today.getFirstDayOfWeek() ;//一个星期的星期几为第一天
16         int curWeekday = today.get(Calendar.DAY_OF_WEEK) ;//今天为这个星期的第几天
17         int indent = 0 ; //缩进,显示上个月的日期
18         
19         while(weekday != curWeekday) {
20             today.add(Calendar.DAY_OF_MONTH, -1);
21             curWeekday = today.get(Calendar.DAY_OF_WEEK) ;
22             indent++ ;
23         }
24         
25         String[] weekdayNames = new DateFormatSymbols().getShortWeekdays() ; 
26         
27         for (String weekdayName : weekdayNames) {
28             if(!"".equals(weekdayName.trim()))
29                 System.out.print(weekdayName + "\t");
30         }
31         
32         System.out.println();
33         
34         for(int i =  0 ; i< indent ;i++) {//打印上个月的几天
35             System.out.print(today.get(Calendar.DAY_OF_MONTH) + "\t\t");
36             today.add(Calendar.DAY_OF_MONTH, 1);
37         }
38         
39         do{
40             int day = today.get(Calendar.DAY_OF_MONTH) ;
41             System.out.print(day + "\t\t");
42             today.add(Calendar.DAY_OF_MONTH, 1) ;
43             curWeekday = today.get(Calendar.DAY_OF_WEEK) ;
44             if(curWeekday == weekday)
45                 System.out.println();
46         }while(today.get(Calendar.MONTH) == curMonth) ;
47         
48     }
49 }