如何使用java8

Question

設置一個工作日，我有以下喬達時間代碼設置平日：

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

我怎樣才能做同樣的java.time？我看是沒有setDayOfTheWeek：

LocalDateTime time; 
time.getDayOfWeek() 

Answer 1

使用time.with(TemporalAdjuster)，指定DayOfWeek一個實例，例如

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

Answer 2

您有幾種方式做到這一點：

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

它沒有setDayOfTheWeek因爲LocalDateTime是不變的，所以它沒有制定者修改的對象。 （喬達時間類也是不可變的！）。

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沒有withDayOfWeek(DayOfWeek)方法。然而，它確實有一個一般的with(TemporalAccessor)方法可以用來代替：

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

然而，這也開啓了一個問題，這週三選擇（它實際上變成每週星期天星期一內的日期）。更好的方法是使用一個TemporalAdjuster，使之更加明確：

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

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

這改變基準日之後的日期到下週三。見TemporalAdjusters瞭解可用的選項：

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