LocalDate：

LocalDate date = LocalDate.of(2020, 5, 20);System.out.println("this year is :" + date.getYear());System.out.println("the month is :" + date.getMonth());System.out.println(" the day of month is :" + date.getDayOfMonth());System.out.println("the day of week is :" + date.getDayOfWeek());System.out.println("this month has days :" + date.lengthOfMonth());System.out.println("this year was leap ? :" + date.isLeapYear()) ;LocalDate now = LocalDate.now();System.out.println("the time now is :" + now);

this year is :2020
the month is :MAYthe day of month is :20
the day of week is :WEDNESDAY
this month has days :31
this year was leap ? :true
the time now is :2020-05-19

LoaclTime：

 LocalTime localTime = LocalTime.now();System.out.println("now time is :" + localTime);System.out.println("hour is " + localTime.getHour());System.out.println("minute is " + localTime.getMinute());System.out.println("second is " + localTime.getSecond());

now time is :11:45:18.117740500
hour is 11
minute is 45
second is 18

LocalDateTime

LocalDateTime localDateTime = LocalDateTime.now();System.out.println("now is :" + localDateTime);System.out.println(localDateTime.getDayOfMonth());System.out.println(localDateTime.getDayOfWeek());System.out.println(localDateTime.getDayOfYear());System.out.println(localDateTime.getMonthValue());

now is :2020-05-19T11:49:09.700690500
19
TUESDAY
140
5

2.机器的日期和时间格式

       你可以通过向静态工厂方法ofEpochSecond传递一个代表秒数的值创建一个该类的实例。静态工厂方法ofEpochSecond还有一个增强的重载版本，它接收第二个以纳秒为单位的参数值，对传入作为秒数的参数进行调整。重载的版本会调整纳秒参数，确保保存的纳秒分片在0到999 999 999之间。这意味着下面这些对ofEpochSecond工厂方法的调用会返回几乎同样的Instant对象：

 

 Instant instant = Instant.now();System.out.println(instant);System.out.println(instant.getEpochSecond());//多加了1天时间Instant instant1 = Instant.ofEpochSecond((instant.getEpochSecond() + (long) 60 * 60* 24));System.out.println(instant1);System.out.println(instant1.getEpochSecond());

2020-05-19T04:04:09.401508500Z
1589861049
2020-05-20T04:04:09Z
1589947449

 

 

3.使用 TemporalAdjuster

       截至目前，你所看到的所有日期操作都是相对比较直接的。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。对于最常见的用例，日期和时间API已经提供了大量预定TemporalAdjuster。你可以通过TemporalAdjuster类的静态工厂方法访问它们，如下所示。

 LocalDate date = LocalDate.now();LocalDate localDate = date.with(nextOrSame(DayOfWeek.SUNDAY));System.out.println(localDate);LocalDate localDate4 = date.with(previousOrSame(DayOfWeek.SUNDAY));System.out.println(localDate4);LocalDate localDate1 = localDate.with(lastDayOfMonth());System.out.println(localDate1);//第三周的星期五LocalDate localDate2 = localDate.with(dayOfWeekInMonth(3, DayOfWeek.FRIDAY));System.out.println(localDate2);//当前月的第一个星期一LocalDate localDate3 = localDate.with(firstInMonth(DayOfWeek.MONDAY));System.out.println(localDate3);

2020-05-24
2020-05-17
2020-05-31
2020-05-15
2020-05-04

      正如我们看到的，使用TemporalAdjuster我们可以进行更加复杂的日期操作，而且这些方 法的名称也非常直观，方法名基本就是问题陈述。此外，即使你没有找到符合你要求的预定义的 TemporalAdjuster，创建你自己的TemporalAdjuster也并非难事。实际上，TemporalAdjuster接口只声明了单一的一个方法（这使得它成为了一个函数式接口），定义如下。

TemporalAdjuster接口

@FunctionalInterface 
public interface TemporalAdjuster { Temporal adjustInto(Temporal temporal); 
}

        这意味着TemporalAdjuster接口的实现需要定义如何将一个Temporal对象转换为另一 个Temporal对象。你可以把它看成一个UnaryOperator<Temporal>。

 

       

       设计一个NextWorkingDay类，该类实现了TemporalAdjuster接口，能够计算明天 的日期，同时过滤掉周六和周日这些节假日。格式如下所示：

 如果当天的星期介于周一至周五之间，日期向后移动一天；如果当天是周六或者周日，则 返回下一个周一。

 LocalDate localDate5 = date.with(temporal -> {DayOfWeek dayOfWeek = DayOfWeek.of(temporal.get(ChronoField.DAY_OF_WEEK));int addToDay = 1;if (dayOfWeek == DayOfWeek.FRIDAY)addToDay = 3;else if (dayOfWeek == DayOfWeek.SATURDAY)addToDay = 2;return temporal.plus(addToDay, ChronoUnit.DAYS);});System.out.println(localDate5);

      你大概会希望在你代码的多个地方使用同样的方式去操作日期，为了达到这一目的，我们 建议你像我们的示例那样将它的逻辑封装到一个类中。对于你经常使用的操作，都应该采用类 似的方式，进行封装。最终，你会创建自己的类库，让你和你的团队能轻松地实现代码复用。

        如果你想要使用Lambda表达式定义TemporalAdjuster对象，推荐使用TemporalAdjusters类的静态工厂方法ofDateAdjuster，它接受一个UnaryOperator<LocalDate>  类型的参数，代码如下：

import static java.time.temporal.TemporalAdjusters.*;TemporalAdjuster temporalAdjuster = ofDateAdjuster(temporal -> {DayOfWeek dayOfWeek = DayOfWeek.of(temporal.get(ChronoField.DAY_OF_WEEK));int addToDay = 1;if (dayOfWeek == DayOfWeek.FRIDAY)addToDay = 3;else if (dayOfWeek == DayOfWeek.SATURDAY)addToDay = 2;return temporal.plus(addToDay, ChronoUnit.DAYS);});LocalDate localDate6 = date.with(temporalAdjuster);System.out.println(localDate6);

   

DateTimeFormatter ：线程安全的类

 LocalDate of = LocalDate.of(2019, 6, 20);String format = of.format(DateTimeFormatter.BASIC_ISO_DATE);String format1 = of.format(DateTimeFormatter.ISO_DATE);System.out.println(format);System.out.println(format1);String format2 = of.format(DateTimeFormatter.ISO_LOCAL_DATE);System.out.println(format2);LocalDate parse = LocalDate.parse("20140318", DateTimeFormatter.BASIC_ISO_DATE);System.out.println(parse);LocalDate parse1 = LocalDate.parse("2014-03-18", DateTimeFormatter.ISO_LOCAL_DATE);System.out.println(parse1);DateTimeFormatter dateTimeFormatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");LocalDateTime now = LocalDateTime.now();DateTimeFormatter dateTimeFormatter1 = DateTimeFormatter.ofPattern("yyyy/MM/dd");System.out.println(now.format(dateTimeFormatter1));System.out.println(now.format(dateTimeFormatter));

20190620
2019-06-20
2019-06-20
2014-03-18
2014-03-18
2020/05/19
2020-05-19 16:28:47