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");
