Java 8中的时间处理

Java 8中的时间处理

在Java8中， 新的时间及⽇期API位于java.time包中， 该包中有哪些重要的类。 分别代表了什么？

Instant： 时间戳

Duration： 持续时间， 时间差

LocalDate： 只包含⽇期， ⽐如： 2016-10-20

LocalTime： 只包含时间， ⽐如： 22:15:16

LocalDateTime： 包含⽇期和时间， ⽐如： 2016-10-20 22:15:16

Period： 时间段

ZoneOffset： 时区偏移量， ⽐如： +8:00

ZonedDateTime： 带时区的时间

Clock： 时钟， ⽐如获取⽬前美国纽约的时间

 

LocalTime 和 LocalDate的区别？

LocalDate表⽰⽇期， 年⽉⽇， LocalTime表⽰时间， 时分 秒

 

获取当前时间

在Java8中，使用如下方式获取当前时间：

LocalDate today = LocalDate.now();
int year = today.getYear();
int month = today.getMonthValue();
int day = today.getDayOfMonth();
System.out.printf("Year : %d Month : %d day : %d t %n", year,month, day);

 

创建指定日期的时间

LocalDate date = LocalDate.of(2018, 01, 01);

LocalDateTime create_localDateTime = LocalDateTime.ofEpochSecond(1593488632L, 0, ZoneOffset.ofHours(8));

 

检查闰年

直接使⽤LocalDate的isLeapYear即可判断是否闰年

LocalDate nowDate = LocalDate.now();
//判断闰年
boolean leapYear = nowDate.isLeapYear();

 

时间相隔

Duraction表示：时间的区间，用来度量秒和纳秒之间的时间值

Period表示：一段时间的区间，用来度量年月日和几天之间的时间值

Period period = Period.between(LocalDate.of(2018, 1, 1), LocalDate.of(2019, 2, 2));
System.out.println("Years:" + period.getYears());//1
System.out.println("Months:" + period.getMonths());//1
System.out.println("Days:" + period.getDays());//1
System.out.println("TotalMonths:" + period.toTotalMonths());//13

LocalDateTime ldt1 = LocalDateTime.of(2018, 1, 1, 1, 1);
LocalDateTime ldt2 = LocalDateTime.of(2019, 2, 2, 2, 2);
Duration duration = Duration.between(ldt1, ldt2);
System.out.println("Days:" + duration.toDays());//397
System.out.println("Hours:" + duration.toHours());//9529
System.out.println("Minutes:" + duration.toMinutes());//571741

 

时间比较

System.out.println("ldt1是否在ldt2之前:" + ldt1.isBefore(ldt2));

 

时间加减

LocalDate now = LocalDate.now();
LocalDate now_plusDays_1 = now.plusDays(1);
LocalDate now_plus_Days_1 = now.plus(1, ChronoUnit.DAYS);

// before 5 hours and 30 minutes
LocalDateTime dateTime = LocalDateTime.now().minusHours(5).minusMinutes(30);

 

 

利用DateTimeFormatter 进行LocalDateTime与String互转

{//LocalDateTime转String(LocalDate,LocalTime类似)
    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    LocalDateTime localDateTime = LocalDateTime.now();
    String localDateTimeStr = dtf.format(localDateTime);
    System.out.println("LocalDateTime转成String类型的时间：" + localDateTimeStr);//2020-06-01 13:23:32
    System.out.println("LocalDateTime转成String类型的时间：" + localDateTime.toString());//2020-06-01T13:23:32.430
}
{//String转LocalDateTime(LocalDate,LocalTime类似)
    DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
    LocalDateTime localDateTime = LocalDateTime.parse("2018-06-01 10:12:05", dtf);
    System.out.println("String类型的时间转成LocalDateTime：" + localDateTime);//2018-06-01T10:12:05
}

 

利用Instant 进行LocalDateTime与Date互转

{//LocalDateTime转Date
    LocalDateTime localDateTime = LocalDateTime.now();
    ZoneId zone = ZoneId.systemDefault();
    Instant instant = localDateTime.atZone(zone).toInstant();
    Date nowDate = Date.from(instant);
    System.out.println(nowDate);//Mon Jun 01 13:55:40 CST 2020
}
{//Date转LocalDateTime
    Date nowDate = new Date();
    Instant instant = nowDate.toInstant();
    ZoneId zone = ZoneId.systemDefault();
    LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone);
    System.out.println(localDateTime);//2020-06-01T13:59:21.315
}
{//LocalDate转Date
    LocalDate localDate = LocalDate.now();
    ZoneId zone = ZoneId.systemDefault();
    Instant instant = localDate.atStartOfDay().atZone(zone).toInstant();
    Date nowDate = Date.from(instant);
    System.out.println(nowDate);//Mon Jun 01 00:00:00 CST 2020
}
{//Date转LocalDate
    Date date = new Date();
    Instant instant = date.toInstant();
    ZoneId zone = ZoneId.systemDefault();
    LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone);
    LocalDate localDate = localDateTime.toLocalDate();
    System.out.println(localDate);//2020-06-01
}
{//LocalTime转Date
    LocalTime localTime = LocalTime.now();
    LocalDate localDate = LocalDate.now();
    LocalDateTime localDateTime = LocalDateTime.of(localDate, localTime);
    ZoneId zone = ZoneId.systemDefault();
    Instant instant = localDateTime.atZone(zone).toInstant();
    Date nowDate = Date.from(instant);
    System.out.println(nowDate);//Mon Jun 01 14:24:29 CST 2020
}
{//Date转LocalTime
    Date date = new Date();
    Instant instant = date.toInstant();
    ZoneId zone = ZoneId.systemDefault();
    LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, zone);
    LocalTime localTime = localDateTime.toLocalTime();
    System.out.println(localTime);//14:24:29.686
}

 

LocalDateTime,LocalDate,LocalTime互转

{//LocalDateTime转LocalDate
    LocalDateTime localDateTime = LocalDateTime.now();
    LocalDate localDate = localDateTime.toLocalDate();
    System.out.println(localDate);//2020-06-01
}
{//LocalDate转LocalDateTime
    LocalDate localDate = LocalDate.now();
    ZoneId zone = ZoneId.systemDefault();
    Instant instant = localDate.atStartOfDay().atZone(zone).toInstant();
    Date date = Date.from(instant);
    System.out.println(date);//Mon Jun 01 00:00:00 CST 2020
}
{//LocalDateTime转LocalTime
    LocalDateTime localDateTime = LocalDateTime.now();
    LocalTime localTime = localDateTime.toLocalTime();
    System.out.println(localTime);//14:29:44.243
}
{//LocalTime转LocalDateTime
    LocalTime localTime = LocalTime.now();
    LocalDate localDate = LocalDate.now();
    LocalDateTime localDateTime = LocalDateTime.of(localDate, localTime);
    System.out.println(localDateTime);//2020-06-01T14:31:35.366
}

 

其它

有的时候，你需要进行一些更加复杂的操作，比如，将日期调整到下个周日、下个工作日，或者是本月的最后一天。这时，你可以使用重载版本的with方法，向其传递一个提供了更多定制化选择的TemporalAdjuster对象，更 加 灵 活 地 处 理 日 期。

public static void main(String[] args) {

        LocalDate date = LocalDate.parse("2020-07-07");
        //获取这个月的第一个周日的时间
        System.out.println(date.with(TemporalAdjusters.dayOfWeekInMonth(1, DayOfWeek.SUNDAY)));
        //输出: 2020-07-05

        //获取上个月的最后一周日的时间
        System.out.println(date.with(TemporalAdjusters.dayOfWeekInMonth(0, DayOfWeek.SUNDAY)));
        //输出: 2020-06-28

        //获取这个月的倒数第一个周日的时间
        System.out.println(date.with(TemporalAdjusters.dayOfWeekInMonth(-1, DayOfWeek.SUNDAY)));
        //输出: 2020-07-26

        //获取这个月的第一个周日的时间,上面的dayOfWeekInMonth更灵活,可以定义第几周
        System.out.println(date.with(TemporalAdjusters.firstInMonth(DayOfWeek.SUNDAY)));
        //输出: 2020-07-05

        //明年的第一天
        System.out.println(date.with(TemporalAdjusters.firstDayOfNextYear()));
        //输出: 2021-01-01

        //获取下个周五的时间
        System.out.println(date.with(TemporalAdjusters.next(DayOfWeek.FRIDAY)));
        //输出: 2020-07-10

        //获取本月最后一天
        System.out.println(date.with(TemporalAdjusters.lastDayOfMonth()));
        //输出: 2020-07-31

        //获取本月第一天
        System.out.println(date.with(TemporalAdjusters.firstDayOfMonth()));
        //输出: 2020-07-01

    }

 

public static void main(String[] args) {

        DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
        //一天开始时间
        LocalDateTime todayStart = LocalDateTime.of(LocalDate.now(), LocalTime.MIN);
        String format = todayStart.format(dateTimeFormatter);
        System.out.println("format = " + format);
        //输出: format = 2020-07-07 00:00:00

        //一天结束时间
        LocalDateTime todayEnd = LocalDateTime.of(LocalDate.now(), LocalTime.MAX);
        String format1 = todayEnd.format(dateTimeFormatter);
        System.out.println("format1 = " + format1);
        //输出: format1 = 2020-07-07 23:59:59

        //一天中午时间
        LocalDateTime todayMid = LocalDateTime.of(LocalDate.now(), LocalTime.NOON);
        String format2 = todayMid.format(dateTimeFormatter);
        System.out.println("format2 = " + format2);
        //输出: format2 = 2020-07-07 12:00:00
    }