Java日期计算

1、时间类得作成

//方法一：取系统点间  
DateTime dt1 = new DateTime();  
  
//方法二：通过java.util.Date对象生成  
DateTime dt2 = new DateTime(new Date());  
  
//方法三：指定年月日点分秒生成(参数依次是：年,月,日,时,分,秒,毫秒)  
DateTime dt3 = new DateTime(2012, 5, 20, 13, 14, 0, 0);  
  
//方法四：ISO8601形式生成  
DateTime dt4 = new DateTime("2012-05-20");  
DateTime dt5 = new DateTime("2012-05-20T13:14:00");  
  
//只需要年月日的时候  
LocalDate localDate = new LocalDate(2009, 9, 6);// September 6, 2009  
  
//只需要时分秒毫秒的时候  
LocalTime localTime = new LocalTime(13, 30, 26, 0);// 1:30:26PM 

　2、获取年月日点分秒

DateTime dt = new DateTime();  
//年  
int year = dt.getYear();  
//月  
int month = dt.getMonthOfYear();  
//日  
int day = dt.getDayOfMonth();  
//星期  
int week = dt.getDayOfWeek();  
//点  
int hour = dt.getHourOfDay();  
//分  
int min = dt.getMinuteOfHour();  
//秒  
int sec = dt.getSecondOfMinute();  
//毫秒  
int msec = dt.getMillisOfSecond();  

　3、星期的特殊处理

DateTime dt = new DateTime();  
  
//星期  
switch(dt.getDayOfWeek()) {  
case DateTimeConstants.SUNDAY:  
    System.out.println("星期日");  
    break;  
case DateTimeConstants.MONDAY:  
    System.out.println("星期一");  
    break;  
case DateTimeConstants.TUESDAY:  
    System.out.println("星期二");  
    break;  
case DateTimeConstants.WEDNESDAY:  
    System.out.println("星期三");  
    break;  
case DateTimeConstants.THURSDAY:  
    System.out.println("星期四");  
    break;  
case DateTimeConstants.FRIDAY:  
    System.out.println("星期五");  
    break;  
case DateTimeConstants.SATURDAY:  
    System.out.println("星期六");  
    break;  
}  

　4、与JDK日期对象的转换

DateTime dt = new DateTime();  
  
//转换成java.util.Date对象  
Date d1 = new Date(dt.getMillis());  
Date d2 = dt.toDate();  
  
//转换成java.util.Calendar对象  
Calendar c1 = Calendar.getInstance();  
c1.setTimeInMillis(dt.getMillis());  
Calendar c2 = dt.toCalendar(Locale.getDefault());  

5、日期前后推算

DateTime dt = new DateTime();  
  
//昨天  
DateTime yesterday = dt.minusDays(1);         
//明天  
DateTime tomorrow = dt.plusDays(1);       
//1个月前  
DateTime before1month = dt.minusMonths(1);        
//3个月后  
DateTime after3month = dt.plusMonths(3);          
//2年前  
DateTime before2year = dt.minusYears(2);          
//5年后  
DateTime after5year = dt.plusYears(5); 

6、取特殊日期

DateTime dt = new DateTime();     
  
//月末日期    
DateTime lastday = dt.dayOfMonth().withMaximumValue();  
  
//90天后那周的周一  
DateTime firstday = dt.plusDays(90).dayOfWeek().withMinimumValue(); 

7、时区

//默认设置为日本时间  
DateTimeZone.setDefault(DateTimeZone.forID("Asia/Tokyo"));  
DateTime dt1 = new DateTime();  
  
//伦敦时间  
DateTime dt2 = new DateTime(DateTimeZone.forID("Europe/London"));

8、计算区间

DateTime begin = new DateTime("2012-02-01");  
DateTime end = new DateTime("2012-05-01");  
  
//计算区间毫秒数  
Duration d = new Duration(begin, end);  
long time = d.getMillis();  
  
//计算区间天数  
Period p = new Period(begin, end, PeriodType.days());  
int days = p.getDays();  
  
//计算特定日期是否在该区间内  
Interval i = new Interval(begin, end);  
boolean contained = i.contains(new DateTime("2012-03-01")); 

9、日期比较

DateTime d1 = new DateTime("2012-02-01");  
DateTime d2 = new DateTime("2012-05-01");  
  
//和系统时间比  
boolean b1 = d1.isAfterNow();  
boolean b2 = d1.isBeforeNow();  
boolean b3 = d1.isEqualNow();  
  
//和其他日期比  
boolean f1 = d1.isAfter(d2);  
boolean f2 = d1.isBefore(d2);  
boolean f3 = d1.isEqual(d2); 

10、格式化输出

DateTime dateTime = new DateTime();  
  
String s1 = dateTime.toString("yyyy/MM/dd hh:mm:ss.SSSa");  
String s2 = dateTime.toString("yyyy-MM-dd HH:mm:ss");  
String s3 = dateTime.toString("EEEE dd MMMM, yyyy HH:mm:ssa");  
String s4 = dateTime.toString("yyyy/MM/dd HH:mm ZZZZ");  
String s5 = dateTime.toString("yyyy/MM/dd HH:mm Z");