Java中常用时间的相关方法有哪些

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一、获取当前时间的方式

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

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

```//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）

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));    /*            cn.hutool        hutool-all        5.7.14         */    //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

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

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

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

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

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