前言
在我们java开发中，Date日期这个字段会被经常使用，比如获取当前系统的时间，获取上个月，上一年的时间，以及获取两个日期相差的时分秒数，或者对日期类型进行格式化，等等，等等，下面将给大家详细介绍下Java中常用时间的一些相关方法
一、获取当前时间的方式
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public static void main(String[] args) { //Date Date now = new Date(); System.out.println(now); //java8的时间 LocalDateTime localDateTime = LocalDateTime.now(); System.out.println(localDateTime); Calendar calendar = Calendar.getInstance(); Date time = calendar.getTime(); System.out.println(time); System.out.println("年" + calendar.get(Calendar.YEAR)); System.out.println("月" + (calendar.get(Calendar.MONTH) + 1)); //joda time DateTime dateTime = DateTime.now(); System.out.println(dateTime);} |
获取当前时间可以使用Date LocalDatetime Calendar Datetime
二、获取当月第n天
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public static void main(String[] args) { //建议使用Calendar 可以设置年月日时分秒 Calendar calendar = Calendar.getInstance(); ////当月16 calendar.set(Calendar.DAY_OF_MONTH, 16); System.out.println(calendar.getTime()); //当月16 DateTime now = DateTime.now(); DateTime dateTime = now.withDayOfMonth(16); System.out.println(dateTime); //当月14 LocalDateTime localDateTime = LocalDateTime.now(); System.out.println(localDateTime.withDayOfMonth(14)); //1月11 System.out.println(localDateTime.withMonth(1).withDayOfMonth(11));} |
三、格式化为字符串
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```//使用SimpleDateFormatSimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println(format.format(new Date()));//使用CalendarCalendar calendar = Calendar.getInstance();System.out.println(String.format("%s年%s月%s日%s时%s分%s秒", calendar.get(Calendar.YEAR), calendar.get(Calendar.MONTH) + 1, calendar.get(Calendar.DAY_OF_MONTH), calendar.get(Calendar.HOUR_OF_DAY), calendar.get(Calendar.MINUTE), calendar.get(Calendar.SECOND)));LocalDateTime now = LocalDateTime.now();String str = now.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));System.out.println(str);``` |
四、加减时间（单位可以是秒，小时等）
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public static void main(String[] args) { Date now = new Date(); //加一小时 long time = now.getTime() + (60 * 60 * 1000); System.out.println(new Date(time)); /* <dependency> <groupId>cn.hutool</groupId> <artifactId>hutool-all</artifactId> <version>5.7.14</version> </dependency> */ //引入Hutool 加一小时 System.out.println(DateUtil.offset(now, DateField.HOUR, 1)); //减一小时 System.out.println(DateUtil.offset(now, DateField.HOUR, -1)); LocalDateTime localDateTime = LocalDateTime.now(); System.out.println("加一小时" + localDateTime.plusHours(1)); System.out.println("减一小时" + localDateTime.minusHours(1)); DateTime dateTime = DateTime.now(); System.out.println(dateTime.plusHours(1)); System.out.println(dateTime.minusHours(1));} |
LocalDateTime和DateTime都自带增加和减少时间的方法
五、通过出生日期获取年龄
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public static void main(String[] args) { //时间1990-12-05 DateTime birthDay = DateTime.now().withYear(1990).withMonthOfYear(10).withDayOfMonth(23); System.out.println(birthDay); //获取相差得年 会进行月份和日期比较 如 Years years = Years.yearsBetween(birthDay, new DateTime()); System.out.println(years); System.out.println(years.getYears());} |
还可以使用年份相减，再比较月，日的方法得到生日
六、判断两个时间段是否覆盖
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public static void main(String[] args) { DateTime now = DateTime.now(); DateTime start1 = now; DateTime end1 = now.plusMinutes(1); DateTime start2 = now.plusSeconds(50); DateTime end2 = now.plusMinutes(2); Interval interval1 = new Interval(start1, end1); Interval interval2 = new Interval(start2, end2); System.out.println(interval1.overlaps(interval2)); System.out.println(start1.getMillis() < end2.getMillis() && start2.getMillis() < end1.getMillis());} |
七、求两个时间间隔
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public static void main(String[] args) { DateTime now = DateTime.now(); //开始时间 Date startTime = now.toDate(); //结束时间 Date endTime = now.plusHours(1).toDate(); //1小时 System.out.println("开始时间与结束时间的时间间隔:" + DateUtil.between(startTime, endTime, DateUnit.SECOND)); long time = (endTime.getTime() - startTime.getTime()) / 1000; System.out.println(time);} |
八、UTC时间与北京时间转换
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public static void main(String[] args) throws ParseException { Date now = new Date(); Date utcDate = bj2UTC(now); //utc时间 System.out.println(utcDate); //北京时间 System.out.println(utc2BJ(utcDate)); DateTime dateTime = DateTime.now().withDayOfMonth(1).withHourOfDay(0).withMinuteOfHour(0).withSecondOfMinute(0); System.out.println(dateTime); System.out.println(bj2UTC(dateTime.toDate()));}public static Date bj2UTC(Date date) { if (date == null) { return null; } LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.of("-8")); return Date.from(localDateTime.atOffset(ZoneOffset.UTC).toInstant());}public static Date utc2BJ(Date date) { if (date == null) { return null; } LocalDateTime localDateTime = LocalDateTime.ofInstant(date.toInstant(), ZoneId.of("+8")); return Date.from(localDateTime.atOffset(ZoneOffset.UTC).toInstant());} |
北京时间=UTC+8
总结
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原文链接：https://juejin.cn/post/7022923059992461320
