2021-01-02

Java日期计算常用方法《简述版》

引入依赖

<dependency>  
        <groupId>joda-time</groupId>  
        <artifactId>joda-time</artifactId>  
        <version>2.9.2</version>  
    </dependency>  

1、获取简单日期

		//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(2021, 9, 1);// September 1, 2021 
		  
		//只需要时分秒毫秒的时候  
		LocalTime localTime = new LocalTime(13, 14, 26, 0);// 1:14:26PM  

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();  
		  
		     
		//明天  
		DateTime tomorrow = dt.plusDays(1);   
		//昨天  
		DateTime yesterday = dt.minusDays(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("2021-01-02");  
		DateTime end = new DateTime("2021-01-01");  
		  
		//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("2021-01-01"));  

9、日期比较

		DateTime d1 = new DateTime("2021-01-01");  
		DateTime d2 = new DateTime("2021-01-01");  
		  
		//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");