前言
Instant——它代表的是时间戳
LocalDate——不包含具体时间的日期，比如2014-01-14。它可以用来存储生日，周年纪念日，入职日期等。
LocalTime——它代表的是不含日期的时间
LocalDateTime——它包含了日期及时间，不过还是没有偏移信息或者说时区。
ZonedDateTime——这是一个包含时区的完整的日期时间，偏移量是以UTC/格林威治时间为基准的。
LocalDateTime总结
public static void main(String[] args) { //------------------------------【获取当前时间】--------------------------------------------------- LocalDateTime nowTime = LocalDateTime.now(); //结果：2021-02-20T09:45:44.527 System.out.println(nowTime); //------------------------------【获取年月日】----------------------------------------------------- //【方法1】 String a = nowTime.format(DateTimeFormatter.ISO_DATE); //结果：2021-02-20 System.out.println(a); //【方法2】 String b = nowTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd")); //结果：2021-02-20 System.out.println(b); //------------------------------【获取时分秒】----------------------------------------------------- String c = nowTime.format(DateTimeFormatter.ofPattern("HH:mm:ss")); //结果：09:45:44 System.out.println(c); //------------------------------【获取年月日时分秒毫秒】-------------------------------------------- String d = nowTime.format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss:SSS")); //结果：2021-02-20 09:45:44:527 System.out.println(d); //------------------------------【获取秒数】------------------------------------------------------- Long second = LocalDateTime.now().toEpochSecond(ZoneOffset.of("+8")); //结果：1613785755 System.out.println(second); //------------------------------【获取毫秒数】----------------------------------------------------- Long milliSecond = LocalDateTime.now().toInstant(ZoneOffset.of("+8")).toEpochMilli(); //结果：1613785815633 System.out.println(milliSecond); //------------------------------【毫秒转LocalDateTime】-------------------------------------------- Long longTime = 1613786449976L; LocalDateTime ldt = Instant.ofEpochMilli(longTime).atZone(ZoneId.systemDefault()).toLocalDateTime(); //结果：2021-02-20T10:00:49.976 System.out.println(ldt); //------------------------------【String转LocalDateTime】------------------------------------------ String dateTimeStr = "2021-02-20 09:50:15"; DateTimeFormatter df = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"); LocalDateTime dateTime = LocalDateTime.parse(dateTimeStr, df); //结果：2021-02-20T09:50:15 System.out.println(dateTime); //------------------------------【LocalDateTime转String】------------------------------------------ //除了下面的方法之外,上面类型转换的都可以看成是LocalDateTime转String ZoneOffset.of("+8")意思为：默认时区为东8区 DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"); String dateTime2 = LocalDateTime.now(ZoneOffset.of("+8")).format(formatter); //结果：2021-02-20 09:55:52 System.out.println(dateTime2); //------------------------------【LocalDateTime转Date】-------------------------------------------- Date date = new Date(); LocalDateTime localDateTime = date.toInstant().atOffset(ZoneOffset.of("+8")).toLocalDateTime(); //结果：2021-02-20T09:59:14.719 System.out.println(localDateTime); //------------------------------【Date转LocalDateTime】-------------------------------------------- LocalDateTime localDateTime1 = LocalDateTime.now(); Date date1 = Date.from(localDateTime1.toInstant(ZoneOffset.of("+8"))); //结果：Sat Feb 20 10:00:49 CST 2021 System.out.println(date1); //------------------------------【LocalDateTime获取年】-------------------------------------------- System.out.println("当前时间为："+LocalDateTime.now()+" == "+"2021-02-20T10:23:45.041"); int year = LocalDateTime.now().getYear(); //结果：2021 System.out.println(year); //------------------------------【LocalDateTime获取月】-------------------------------------------- Month month = LocalDateTime.now().getMonth(); //结果：FEBRUARY System.out.println(month); int monthValue = LocalDateTime.now().getMonthValue(); //结果：2 System.out.println(monthValue); //------------------------------【LocalDateTime获取日】-------------------------------------------- int dayOfMonth = LocalDateTime.now().getDayOfMonth(); //结果：20 System.out.println(dayOfMonth); DayOfWeek dayOfWeek = LocalDateTime.now().getDayOfWeek(); //结果：SATURDAY System.out.println(dayOfWeek); int dayOfYear = LocalDateTime.now().getDayOfYear(); //结果：51 System.out.println(dayOfYear); //------------------------------【LocalDateTime获取时】-------------------------------------------- int hour = LocalDateTime.now().getHour(); //结果：10 System.out.println(hour); //------------------------------【LocalDateTime获取分】-------------------------------------------- int minute = LocalDateTime.now().getMinute(); //结果：23 System.out.println(minute); //------------------------------【LocalDateTime获取秒】-------------------------------------------- int second1 = LocalDateTime.now().getSecond(); //结果：45 System.out.println(second1); //------------------------------【LocalDateTime获取特定日期】--------------------------------------- LocalDateTime of = LocalDateTime.of(2021, 2, 20, 10, 37, 20); //结果：2021-02-20T10:37:20 System.out.println(of); //------------------------------【LocalDateTime时间对比】------------------------------------------- LocalDateTime of1 = LocalDateTime.of(2021, 2, 20, 10, 37, 20); LocalDateTime of2 = LocalDateTime.of(2021, 2, 20, 10, 37, 22); LocalDateTime of3 = LocalDateTime.of(2021, 2, 20, 10, 37, 22); //【方法1】 //结果：false System.out.println(of1.equals(of2)); //结果：true System.out.println(of2.equals(of3)); //结果：-1 of1 < of2 System.out.println(of1.compareTo(of2)); //结果：0 of2 = of3 System.out.println(of2.compareTo(of3)); //结果：1 of3 > of1 System.out.println(of3.compareTo(of1)); //【方法2】 //结果：false System.out.println(of1.isAfter(of2)); //结果：true System.out.println(of1.isBefore(of2)); //结果：true System.out.println(of2.isEqual(of3)); //------------------------------【LocalDateTime获取一天前/后日期】----------------------------------- LocalDateTime localDateTime2 = LocalDateTime.now().plusDays(1); //结果：2021-02-21T10:48:26.911 System.out.println(localDateTime2); LocalDateTime localDateTime3 = LocalDateTime.now().plusDays(-1); //结果：2021-02-19T10:48:26.911 System.out.println(localDateTime3); //------------------------------【LocalDateTime获取一小时前/后日期】----------------------------------- LocalDateTime localDateTime4 = LocalDateTime.now().plusHours(1); //结果：2021-02-20T11:49:32.320 System.out.println(localDateTime4); LocalDateTime localDateTime5 = LocalDateTime.now().plusHours(-1); //结果：2021-02-20T09:49:32.320 System.out.println(localDateTime5); //------------------------------【LocalDateTime获取一年前/后日期】------------------------------------- LocalDateTime localDateTime6 = LocalDateTime.now().plusYears(1); //结果：2022-02-20T10:51:47.585 System.out.println(localDateTime6); LocalDateTime localDateTime7 = LocalDateTime.now().plusYears(-1); //结果：2020-02-20T10:51:47.585 System.out.println(localDateTime7); //------------------------------【LocalDateTime获取一分钟前/后日期】----------------------------------- LocalDateTime localDateTime8 = LocalDateTime.now().plusMinutes(1); //结果：2021-02-20T13:54:39.209 System.out.println(localDateTime8); LocalDateTime localDateTime9 = LocalDateTime.now().plusMinutes(-1); //结果：2021-02-20T13:52:39.209 System.out.println(localDateTime9); //------------------------------【LocalDateTime获取一月前/后日期】------------------------------------- LocalDateTime localDateTime10 = LocalDateTime.now().plusMonths(1); //结果：2021-03-20T13:55:12.718 System.out.println(localDateTime10); LocalDateTime localDateTime11 = LocalDateTime.now().plusMonths(-1); //结果：2021-01-20T13:55:12.718 System.out.println(localDateTime11); //------------------------------【LocalDateTime获取一秒前/后日期】------------------------------------- LocalDateTime localDateTime12 = LocalDateTime.now().plusSeconds(1); //结果：2021-02-20T13:57:51.966 System.out.println(localDateTime12); LocalDateTime localDateTime13 = LocalDateTime.now().plusSeconds(-1); //结果：2021-02-20T13:57:49.966 System.out.println(localDateTime13); //------------------------------【LocalDateTime获取一周前/后日期】------------------------------------- LocalDateTime localDateTime14 = LocalDateTime.now().plusWeeks(1); //结果：2021-02-27T13:59:46.615 System.out.println(localDateTime14); LocalDateTime localDateTime15 = LocalDateTime.now().plusWeeks(-1); //结果：2021-02-13T13:59:46.615 System.out.println(localDateTime15); }
参考：
https://www.cnblogs.com/comeboo/p/5378922.html