如何使用java8

Question

设置一个工作日，我有以下乔达时间代码设置平日：

LocalDateTime localDateTime = new LocalDateTime(2016, 1, 1, 20,39); 
LocalDateTime localDateTime1 = localDateTime.withDayOfWeek(7); 

我怎样才能做同样的java.time？我看是没有setDayOfTheWeek：

LocalDateTime time; 
time.getDayOfWeek() 

Answer 1

使用time.with(TemporalAdjuster)，指定DayOfWeek一个实例，例如

LocalDateTime time1 = time.with(DayOfWeek.FRIDAY); 

Answer 2

您有几种方式做到这一点：

LocalDateTime localDateTime = LocalDateTime.of(2016, 1, 1, 20, 39); 

LocalDateTime ldt1 = localDateTime.with(ChronoField.DAY_OF_WEEK, 7); 
LocalDateTime ldt2 = localDateTime.with(DayOfWeek.of(7)); 
//Or, more readable, as suggested by @AndyTurner 
LocalDateTime ldt3 = localDateTime.with(DayOfWeek.SUNDAY); 

Answer 3

它没有setDayOfTheWeek因为LocalDateTime是不变的，所以它没有制定者修改的对象。 （乔达时间类也是不可变的！）。

使用此Java中8：

LocalDateTime localDateTime = LocalDateTime.of(2016, 1, 1, 20,39); 
LocalDateTime localDateTime1 = localDateTime.with(DayOfWeek.SUNDAY); 

Answer 4

的java.time API没有withDayOfWeek(DayOfWeek)方法。然而，它确实有一个一般的with(TemporalAccessor)方法可以用来代替：

LocalDateTime dt = base.with(DayOfWeek.WEDNESDAY); 

然而，这也开启了一个问题，这周三选择（它实际上变成每周星期天星期一内的日期）。更好的方法是使用一个TemporalAdjuster，使之更加明确：

import static java.time.DayOfWeek.WEDNESDAY; 
import static java.time.temporal.TemporalAdjusters.next; 

LocalDateTime dt = base.with(next(WEDNESDAY)); 

这改变基准日之后的日期到下周三。见TemporalAdjusters了解可用的选项：

• next(DayOfWeek)
• nextOrSame(DayOfWeek)
• previous(DayOfWeek)
• previousOrSame(DayOfWeek)
• firstInMonth(DayOfWeek)
• lastInMonth(DayOfWeek)
• dayOfWeekInMonth(int, DayOfWeek)