java.time 中的年-周-日？

Question

java.time classes, or its extension ThreeTen-Extra, for a week dates 是否有支持，特别是年-周-日，例如 2009-W53-7 即 2010 年 1 月 3 日星期日。

至于年周没有星期：

My Answer to the Question, java get week of year for given a date, explains using IsoFields 处理年-周。
ThreeTen-Extra project that extends the java.time classes offers the YearWeek class。

但是如何表示星期几呢？

Answer 1

参见IsoFields class, which allows the week-based year and week of week-based year to be queried. There is also a dedicated formatter ISO_WEEK_DATE。

DayOfWeek enum tells you the number of the day-of-week, 1-7 for Monday to Sunday. Call LocalDate::getDayOfWeek and then DayOfWeek::getValue.

LocalDate ld = LocalDate.now( ZoneId.of( "America/Montreal" ) ) ;

2016-12-07

int weekOfWeekBasedYear = ld.get( IsoFields.WEEK_OF_WEEK_BASED_YEAR ) ;
int yearOfWeekBasedYear = ld.get( IsoFields.WEEK_BASED_YEAR ) ;
int dayOfWeek = ld.getDayOfWeek().getValue();

使用这些部分构建标准字符串 ISO 8601 week date formats。

String yearWeek = yearOfWeekBasedYear + "-W" + String.format( "%02d", weekOfWeekBasedYear ) ;

2016-W49

String yearWeekDay = yearWeek + "-" + dayOfWeek ;

2016-W49-3

或者，让预定义的 DateTimeFormatter.ISO_WEEK_DATE 完成工作。

String ywd = ld.format( DateTimeFormatter.ISO_WEEK_DATE );

2016-W49-3

同一个格式化程序可以解析此类标准字符串。

String input = "2016-W49-3" ;
LocalDate ldParsed = LocalDate.parse( input , DateTimeFormatter.ISO_WEEK_DATE ) ;

2016-12-07

java.time 中的年-周-日？

Year-Week-Day in java.time?

java-time

iso8601

week-number