blocks|key|139084|text|试一试|type|unstyled|depth|inlineStyleRanges|entityRanges|data|139085|System.out.println(now.with(DayOfWeek.MONDAY));|code-block|syntax|javascript|139086|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try

<pre><code>System.out.println(now.with(DayOfWeek.MONDAY));
</code></pre>

blocks|key|2713368|text|感谢this+question中的come+from。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|2713369|Calendar+cal+=+Calendar.getInstance();
++++++++cal.set(Calendar.HOUR_OF_DAY,+0);+//+!+clear+would+not+reset+the+hour+of+day+!
++++++++cal.clear(Calendar.MINUTE);
++++++++cal.clear(Calendar.SECOND);
++++++++cal.clear(Calendar.MILLISECOND);

++++++++//+get+start+of+this+week+in+milliseconds
++++++++cal.set(Calendar.DAY_OF_WEEK,+cal.getFirstDayOfWeek());
++++++++System.out.println("Start+of+this+week:+++++++"+%2B+cal.getTime());
++++++++System.out.println("...+in+milliseconds:++++++"+%2B+cal.getTimeInMillis());|code-block|syntax|javascript|2713370|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/2937086/how-to-get-the-first-day-of-the-current-week-and-month|1|https://stackoverflow.com/users/245813/come-from^0|2|D|0|H|9|1|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]|$A|W|B|X|1|Y]]|C|$]]|$1|D|3|E|5|F|7|Z|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|10|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]|Q|$5|L|M|N|C|$O|R]]]]

Thanks to <a href="https://stackoverflow.com/users/245813/come-from">come from</a> in <a href="https://stackoverflow.com/questions/2937086/how-to-get-the-first-day-of-the-current-week-and-month">this question</a>.

<pre><code>Calendar cal = Calendar.getInstance();
 cal.set(Calendar.HOUR_OF_DAY, 0); // ! clear would not reset the hour of day !
 cal.clear(Calendar.MINUTE);
 cal.clear(Calendar.SECOND);
 cal.clear(Calendar.MILLISECOND);

 // get start of this week in milliseconds
 cal.set(Calendar.DAY_OF_WEEK, cal.getFirstDayOfWeek());
 System.out.println("Start of this week: " + cal.getTime());
 System.out.println("... in milliseconds: " + cal.getTimeInMillis());
</code></pre>

blocks|key|141556|text|请注意，表达式System.out.println(now.with(DayOfWeek.MONDAY))是独立于区域设置的，因为它使用ISO8601，因此它总是向后跳到上个星期一(或者在日期已经指向星期一的情况下停留在星期一)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|141557|因此，在美国或其他一些国家-一周从周日开始-它可能不会像你预期的那样工作-+now.with(DayOfWeek.MONDAY)+不会将跳转到周一，以防日期指向周日。|BOLD|141558|如果需要解决这些问题，最好使用本地化字段WeekFields.dayOfWeek()|141559|LocalDate+now+=+LocalDate.now();
TemporalField+fieldISO+=+WeekFields.of(Locale.FRANCE).dayOfWeek();
System.out.println(now.with(fieldISO,+1));+//+2015-02-09+(Monday)

TemporalField+fieldUS+=+WeekFields.of(Locale.US).dayOfWeek();
System.out.println(now.with(fieldUS,+1));+//+2015-02-08+(Sunday)|code-block|syntax|javascript|141560|另一个例子是由于下面的评论：|141561|LocalDate+ld+=+LocalDate.of(2017,+8,+18);+//+Friday+as+original+date

System.out.println(
++++ld.with(DayOfWeek.SUNDAY));+//+2017-08-20+(2+days+later+according+to+ISO)

//+Now+let's+again+set+the+date+to+Sunday,+but+this+time+in+a+localized+way...
//+the+method+dayOfWeek()+uses+localized+numbering+(Sunday+=+1+in+US+and+=+7+in+France)

System.out.println(ld.with(WeekFields.of(Locale.US).dayOfWeek(),+1L));+//+2017-08-13
System.out.println(ld.with(WeekFields.of(Locale.FRANCE).dayOfWeek(),+7L));+//+2017-08-20|141562|美国的例子很清楚地表明，居住在美国的人希望去的是最后一天，而不是下周日，因为星期天在美国被认为是一周的第一天。简单的基于ISO的表达式with(DayOfWeek.SUNDAY)忽略了这个本地化问题。|141563|entityMap|0|LINK|mutability|MUTABLE|url|http://docs.oracle.com/javase/8/docs/api/java/time/temporal/WeekFields.html#dayOfWeek--^0|7|1A|0|12|Q|1T|3|0|K|M|0|0|0|0|0|1V|M|0^^$0|@$1|2|3|4|5|6|7|13|8|@$9|14|A|15|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|16|8|@$9|17|A|18|B|C]|$9|19|A|1A|B|H]]|D|@]|E|$]]|$1|I|3|J|5|6|7|1B|8|@]|D|@$9|1C|A|1D|1|1E]]|E|$]]|$1|K|3|L|5|M|7|1F|8|@]|D|@]|E|$N|O]]|$1|P|3|Q|5|6|7|1G|8|@]|D|@]|E|$]]|$1|R|3|S|5|M|7|1H|8|@]|D|@]|E|$N|O]]|$1|T|3|U|5|6|7|1I|8|@$9|1J|A|1K|B|C]]|D|@]|E|$]]|$1|V|3|-4|5|6|7|1L|8|@]|D|@]|E|$]]]|W|$X|$5|Y|Z|10|E|$11|12]]]]

Note that the expression <code>System.out.println(now.with(DayOfWeek.MONDAY))</code> is locale-independent as it uses ISO-8601, therefore it always jumps backwards to last Monday (or stays on Monday in case date points to Monday already). 

As such in US or some other countries - where week starts on Sunday - it may not work as you would expect - <code>now.with(DayOfWeek.MONDAY)</code> will not jump forward to Monday, in case date points to Sunday.

In case you need to address these concerns, it is better to use the localized field <a href="http://docs.oracle.com/javase/8/docs/api/java/time/temporal/WeekFields.html#dayOfWeek--" rel="noreferrer">WeekFields.dayOfWeek()</a>:

<pre><code>LocalDate now = LocalDate.now();
TemporalField fieldISO = WeekFields.of(Locale.FRANCE).dayOfWeek();
System.out.println(now.with(fieldISO, 1)); // 2015-02-09 (Monday)

TemporalField fieldUS = WeekFields.of(Locale.US).dayOfWeek();
System.out.println(now.with(fieldUS, 1)); // 2015-02-08 (Sunday)
</code></pre>

Another example due to comments below:

<pre><code>LocalDate ld = LocalDate.of(2017, 8, 18); // Friday as original date

System.out.println(
 ld.with(DayOfWeek.SUNDAY)); // 2017-08-20 (2 days later according to ISO)

// Now let's again set the date to Sunday, but this time in a localized way...
// the method dayOfWeek() uses localized numbering (Sunday = 1 in US and = 7 in France)

System.out.println(ld.with(WeekFields.of(Locale.US).dayOfWeek(), 1L)); // 2017-08-13
System.out.println(ld.with(WeekFields.of(Locale.FRANCE).dayOfWeek(), 7L)); // 2017-08-20
</code></pre>

The US-example makes pretty clear that someone residing in US would expect to go to last and not to next Sunday because Sunday is considered as first day of week in US. The simple ISO-based expression <code>with(DayOfWeek.SUNDAY)</code> ignores this localization issue.

blocks|key|142657|text|正如Ray的correct+Answer所说，您可以调用with并传递DayOfWeek枚举。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|142658|时区|142659|请注意，在确定“今天”的日期时，时区至关重要。在任何时刻，日期都会随你在地球上所处的位置而变化。|142660|ZoneId+zoneId+=+ZoneId.of+(+"America/Montreal"+);
LocalDate+firstDayOfThisWeek+=+LocalDate.now+(+zoneId+).with+(+DayOfWeek.MONDAY+);|code-block|syntax|javascript|142661|如果不指定时区，JVM的当前缺省时区将以静默方式应用。注意:在运行过程中，默认设置随时都可能改变！最好指定your+desired/expected+time+zone。|142662|ZonedDateTime|142663|您可以将时区(+ZoneId)应用于LocalDate，以获得表示一周的第一个时刻的ZonedDateTime。|142664|ZonedDateTime+thisWeekStart+=+firstDayOfThisWeek.atStartOfDay+(+zoneId+);|142665|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/28450817/642706|1|http://docs.oracle.com/javase/8/docs/api/java/time/DayOfWeek.html|2|https://en.wikipedia.org/wiki/List_of_tz_database_time_zones|3|http://docs.oracle.com/javase/8/docs/api/java/time/ZoneId.html|4|http://docs.oracle.com/javase/8/docs/api/java/time/LocalDate.html|5|http://docs.oracle.com/javase/8/docs/api/java/time/ZonedDateTime.html^0|S|4|Z|9|6|E|0|Z|9|1|0|0|0|0|1H|V|2|0|0|D|0|8|6|I|9|16|D|8|6|3|I|9|4|16|D|5|0|0^^$0|@$1|2|3|4|5|6|7|1E|8|@$9|1F|A|1G|B|C]|$9|1H|A|1I|B|C]]|D|@$9|1J|A|1K|1|1L]|$9|1M|A|1N|1|1O]]|E|$]]|$1|F|3|G|5|6|7|1P|8|@]|D|@]|E|$]]|$1|H|3|I|5|6|7|1Q|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|1R|8|@]|D|@]|E|$M|N]]|$1|O|3|P|5|6|7|1S|8|@]|D|@$9|1T|A|1U|1|1V]]|E|$]]|$1|Q|3|R|5|6|7|1W|8|@$9|1X|A|1Y|B|C]]|D|@]|E|$]]|$1|S|3|T|5|6|7|1Z|8|@$9|20|A|21|B|C]|$9|22|A|23|B|C]|$9|24|A|25|B|C]]|D|@$9|26|A|27|1|28]|$9|29|A|2A|1|2B]|$9|2C|A|2D|1|2E]]|E|$]]|$1|U|3|V|5|L|7|2F|8|@]|D|@]|E|$M|N]]|$1|W|3|-4|5|6|7|2G|8|@]|D|@]|E|$]]]|X|$Y|$5|Z|10|11|E|$12|13]]|14|$5|Z|10|11|E|$12|15]]|16|$5|Z|10|11|E|$12|17]]|18|$5|Z|10|11|E|$12|19]]|1A|$5|Z|10|11|E|$12|1B]]|1C|$5|Z|10|11|E|$12|1D]]]]

As the <a href="https://stackoverflow.com/a/28450817/642706">correct Answer</a> by Ray says, you can call <code>with</code> and pass the <a href="http://docs.oracle.com/javase/8/docs/api/java/time/DayOfWeek.html" rel="nofollow noreferrer"><code>DayOfWeek</code></a> enum. 

<h1>Time zone</h1>

Note that time zone is crucial in determining the date of "today". At any moment the date varies by where you are standing on the globe.

<pre><code>ZoneId zoneId = ZoneId.of ( "America/Montreal" );
LocalDate firstDayOfThisWeek = LocalDate.now ( zoneId ).with ( DayOfWeek.MONDAY );
</code></pre>

If you do not specify a time zone, the JVM’s current default time zone is silently applied. Beware: That default can change at any moment during runtime! Better to specify <a href="https://en.wikipedia.org/wiki/List_of_tz_database_time_zones" rel="nofollow noreferrer">your desired/expected time zone</a>.

<h1><code>ZonedDateTime</code></h1>

You can apply a time zone (a <a href="http://docs.oracle.com/javase/8/docs/api/java/time/ZoneId.html" rel="nofollow noreferrer"><code>ZoneId</code></a>) to your <a href="http://docs.oracle.com/javase/8/docs/api/java/time/LocalDate.html" rel="nofollow noreferrer"><code>LocalDate</code></a> to get a <a href="http://docs.oracle.com/javase/8/docs/api/java/time/ZonedDateTime.html" rel="nofollow noreferrer"><code>ZonedDateTime</code></a> representing the first moment of the week.

<pre><code>ZonedDateTime thisWeekStart = firstDayOfThisWeek.atStartOfDay ( zoneId );
</code></pre>

blocks|key|141603|text|有了Joda+Time，你会怎么想|type|unstyled|depth|inlineStyleRanges|entityRanges|data|141604|now.toString("EEEE",+locale)|code-block|syntax|javascript|141605|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

With Joda Time, what do you think of

<pre><code>now.toString("EEEE", locale)
</code></pre>

blocks|key|141617|text|尽管前面有所有的答案，但我仍然不得不深入研究Java8在做什么，所以下面是我发现的最直观的方法：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|141618|141619|+LocalDate实现了|blockquote|141620|141621|with(TemporalField+field,+long+newValue)|offset|length|style|CODE|141622|返回与更改了指定字段的此对象具有相同类型的对象。|141623|141624|因此，我们必须告诉它我们想要更改(DAY_OF_WEEK)+LocalDate的哪个日期部分以及更改为什么值。|141625|如果您怀疑一周中的日期可能是从0到6或从1到7：|141626|++++System.out.printf("first+day+of+week+(0+or+1)+==+%25d+\n",
++++++++++++ChronoField.DAY_OF_WEEK.range().getMinimum());|code-block|syntax|javascript|141627|first+day+of+week+(0+or+1)+==+1+|141628|我必须确定我的JDK为默认值提供了什么-+YMMV：|141629|++++System.out.printf("default+zone+offset==[%25s]\n",
++++++++++++ZoneId.systemDefault());
++++System.out.printf("1st+day+of+week==%25s\n",
++++++++++++WeekFields.of(Locale.getDefault()).getFirstDayOfWeek());|141630|default+zone+offset==[Europe/London]
1st+day+of+week==MONDAY|141631|因此，如果我基于这些默认值执行一些代码，如下所示：|141632|++++LocalDate+localDate+=+LocalDate.now();
++++System.out.printf("localDate+==+%25s+\n",+localDate);
++++System.out.printf("localdate+first+day+of+week+==+%25s+(%25s)+\n",
++++++++++++localDate.with(ChronoField.DAY_OF_WEEK,+1),
++++++++++++localDate.with(ChronoField.DAY_OF_WEEK,+1).getDayOfWeek());|141633|localDate+==+2017-10-24+
localdate+first+day+of+week+==+2017-10-23+(MONDAY)+|141634|然后Java使用ChronoField.DAY_OF_WEEK，它不仅定义了我们想要更改日期的哪一部分，而且还定义了如何更改它。|141635|因此，如果我们希望我们的代码处理用户指定的每周的第一天，我们可以使用WeekFields.of()工厂方法创建我们自己的定义，即如何完成基于周的计算。|141636|使用它，我们可以将我们自己的dayOfWeek参数传递给with()，以按照我们想要的方式进行日期计算：|141637|++++TemporalField+myWeek+=+WeekFields.of(DayOfWeek.SUNDAY,+1).dayOfWeek();
++++System.out.printf("configured+localdate+first+day+of+week+==+%25s+(%25s)+\n",
++++++++++++localDate.with(myWeek,+1),
++++++++++++localDate.with(myWeek,+1).getDayOfWeek());|141638|configured+localdate+first+day+of+week+==+2017-10-22+(SUNDAY)+|141639|要了解更多信息，请查看LocalDate.with()中的代码，它非常有趣。|141640|entityMap^0|0|0|0|0|0|14|0|0|0|H|B|U|9|0|0|0|0|0|0|0|0|0|0|8|N|0|Y|F|0|E|9|S|6|0|0|0|B|G|0^^$0|@$1|2|3|4|5|6|7|1Q|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|1R|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|1S|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|1T|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|1U|8|@$I|1V|J|1W|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|1X|8|@]|9|@]|A|$]]|$1|O|3|-4|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|1Z|8|@$I|20|J|21|K|L]|$I|22|J|23|K|L]]|9|@]|A|$]]|$1|R|3|S|5|6|7|24|8|@]|9|@]|A|$]]|$1|T|3|U|5|V|7|25|8|@]|9|@]|A|$W|X]]|$1|Y|3|Z|5|V|7|26|8|@]|9|@]|A|$W|X]]|$1|10|3|11|5|6|7|27|8|@]|9|@]|A|$]]|$1|12|3|13|5|V|7|28|8|@]|9|@]|A|$W|X]]|$1|14|3|15|5|V|7|29|8|@]|9|@]|A|$W|X]]|$1|16|3|17|5|6|7|2A|8|@]|9|@]|A|$]]|$1|18|3|19|5|V|7|2B|8|@]|9|@]|A|$W|X]]|$1|1A|3|1B|5|V|7|2C|8|@]|9|@]|A|$W|X]]|$1|1C|3|1D|5|6|7|2D|8|@$I|2E|J|2F|K|L]]|9|@]|A|$]]|$1|1E|3|1F|5|6|7|2G|8|@$I|2H|J|2I|K|L]]|9|@]|A|$]]|$1|1G|3|1H|5|6|7|2J|8|@$I|2K|J|2L|K|L]|$I|2M|J|2N|K|L]]|9|@]|A|$]]|$1|1I|3|1J|5|V|7|2O|8|@]|9|@]|A|$W|X]]|$1|1K|3|1L|5|V|7|2P|8|@]|9|@]|A|$W|X]]|$1|1M|3|1N|5|6|7|2Q|8|@$I|2R|J|2S|K|L]]|9|@]|A|$]]|$1|1O|3|-4|5|6|7|2T|8|@]|9|@]|A|$]]]|1P|$]]

Despite all the previous answers, I still had to dig around to work out what Java8 was doing, so here is what I found to be the most intuitive way of doing it:

<blockquote>
 LocalDate implements <a href="https://docs.oracle.com/javase/8/docs/api/index.html" rel="noreferrer">Temporal</a>
 
 <code>with(TemporalField field, long newValue)</code>
 
 Returns an object of the same type as this object with the specified field altered.
</blockquote>

So we have to tell it which date part of <code>LocalDate</code> we want to change (<code>DAY_OF_WEEK</code>) and change to what value.

In case you had doubts that the days in the week might be counted from 0 to 6 or from 1 to 7:

<pre class="lang-java prettyprint-override"><code> System.out.printf("first day of week (0 or 1) == %d \n",
 ChronoField.DAY_OF_WEEK.range().getMinimum());
</code></pre>

<pre class="lang-none prettyprint-override"><code>first day of week (0 or 1) == 1 
</code></pre>

I had to nail down what my JDK was providing for defaults - YMMV:

<pre class="lang-java prettyprint-override"><code> System.out.printf("default zone offset==[%s]\n",
 ZoneId.systemDefault());
 System.out.printf("1st day of week==%s\n",
 WeekFields.of(Locale.getDefault()).getFirstDayOfWeek());
</code></pre>

<pre class="lang-none prettyprint-override"><code>default zone offset==[Europe/London]
1st day of week==MONDAY
</code></pre>

So if I execute some code based on these defaults, like so:

<pre class="lang-java prettyprint-override"><code> LocalDate localDate = LocalDate.now();
 System.out.printf("localDate == %s \n", localDate);
 System.out.printf("localdate first day of week == %s (%s) \n",
 localDate.with(ChronoField.DAY_OF_WEEK, 1),
 localDate.with(ChronoField.DAY_OF_WEEK, 1).getDayOfWeek());
</code></pre>

<pre class="lang-none prettyprint-override"><code>localDate == 2017-10-24 
localdate first day of week == 2017-10-23 (MONDAY) 
</code></pre>

then Java goes with <code>ChronoField.DAY_OF_WEEK</code> which not only defines which part of the date we want to alter, but also how to alter it. 

So if we want our code to deal with whatever the user specifies as the first day of the week, we create our own definition of how week-based calculations are meant to be done, using the <code>WeekFields.of()</code> factory method. 

Using this we can pass in our own <code>dayOfWeek</code> parameter to <code>with()</code> to do the date calculation the way we want:

<pre class="lang-java prettyprint-override"><code> TemporalField myWeek = WeekFields.of(DayOfWeek.SUNDAY, 1).dayOfWeek();
 System.out.printf("configured localdate first day of week == %s (%s) \n",
 localDate.with(myWeek, 1),
 localDate.with(myWeek, 1).getDayOfWeek());
</code></pre>

<pre class="lang-none prettyprint-override"><code>configured localdate first day of week == 2017-10-22 (SUNDAY) 
</code></pre>

For more insight, have a look at the code in <code>LocalDate.with()</code>, it's quite interesting.

blocks|key|140489|text|LocalDate似乎没有这个功能，但是WeekFields+(来自java-8API)有()。所以你可以这样做：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|140490|WeekFields.of(Locale.getDefault()).firstDayOfWeek.value|code-block|syntax|javascript|140491|这将返回一周的第一天的值，从1作为星期一开始，以7作为星期天结束。|140492|使用示例(在Kotlin中)，获取设置了dayOfWeek的新LocalDate，在时间上向后而不是向前：|140493|/**@param+targetDayOfWeek+day+of+week+to+go+to,+starting+from+1+as+Monday+(and+7+is+Sunday)+*/
fun+LocalDate.minusDaysToDayOfWeek(targetDayOfWeek:+Int+=+WeekFields.of(Locale.getDefault()).firstDayOfWeek.value):+LocalDate+{
++++//conversion+so+that+Sunday+is+0,+Monday+is+1,+etc:
++++val+diffDays+=+(dayOfWeek.value+%25+7)+-+(targetDayOfWeek+%25+7)
++++val+result+=+when+{
++++++++diffDays+==+0+->+this
++++++++diffDays+<+0+->+minusDays((7+%2B+diffDays).toLong())
++++++++else+->+minusDays(diffDays.toLong())
++++}
++++return+result
}|140494|示例输入-输出：|140495|2017-12-31+->+2017-12-31
2018-01-01+->+2017-12-31
2018-01-02+->+2017-12-31
2018-01-03+->+2017-12-31
2018-01-04+->+2017-12-31
2018-01-05+->+2017-12-31
2018-01-06+->+2017-12-31
2018-01-07+->+2018-01-07
2018-01-08+->+2018-01-07
2018-01-09+->+2018-01-07
2018-01-10+->+2018-01-07
2018-01-11+->+2018-01-07
2018-01-12+->+2018-01-07
2018-01-13+->+2018-01-07
2018-01-14+->+2018-01-14
2018-01-15+->+2018-01-14|140496|下面是一个示例函数，可以及时前进到一周的目标日期：|140497|fun+LocalDate.plusDaysToDayOfWeek(targetDayOfWeek:+Int+=+getLastDayOfWeek()):+LocalDate+{
++++val+diffDays+=+(targetDayOfWeek+%25+7)+-+(dayOfWeek.value+%25+7)
++++val+result+=+when+{
++++++++diffDays+==+0+->+this
++++++++diffDays+<+0+->+plusDays((7+%2B+diffDays).toLong())
++++++++else+->+plusDays(diffDays.toLong())
++++}
++++return+result
}

/**@return+the++last+day+of+week,+when+1+is+Monday+...+7+is+Sunday)+*/
@JvmStatic
fun+getLastDayOfWeek(firstDayOfWeek:+DayOfWeek+=+WeekFields.of(Locale.getDefault()).firstDayOfWeek):+Int+{
++++return+when+(firstDayOfWeek)+{
++++++++DayOfWeek.MONDAY+->+DayOfWeek.SUNDAY.value
++++++++else+->+firstDayOfWeek.value+-+1
++++}
}|140498|顺便说一句，奇怪的是，我认为新API的幕后代码实际上使用了Calendar类……|140499|如果你讨厌使用LocalDate中的dayOfWeek+(我也是这样)，而你更喜欢日历中使用的日历，你可以使用这些简单的转换器：|140500|fun+DayOfWeek.toCalendarDayOfWeek():+Int+{
++++return+when+(this)+{
++++++++DayOfWeek.SATURDAY+->+Calendar.SATURDAY
++++++++else+->+(this.value+%2B+1)+%25+7
++++}
}

@JvmStatic
fun+convertLocalDateDayOfWeekToCalendarDayOfWeek(localDateDayOfWeek:+Int):+Int+{
++++return+when+(localDateDayOfWeek)+{
++++++++DayOfWeek.SATURDAY.value+->+Calendar.SATURDAY
++++++++else+->+(localDateDayOfWeek+%2B+1)+%25+7
++++}
}

@JvmStatic
fun+convertFromCalendarDayOfWeekToLocalDateDayOfWeek(calendarDayOfWeek:+Int):+Int+{
++++return+when+(calendarDayOfWeek)+{
++++++++Calendar.SUNDAY+->+DayOfWeek.SUNDAY.value
++++++++else+->+calendarDayOfWeek+-+1
++++}
}|140501|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|14|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|15|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|16|8|@]|9|@]|A|$E|F]]|$1|M|3|N|5|6|7|17|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|18|8|@]|9|@]|A|$E|F]]|$1|Q|3|R|5|6|7|19|8|@]|9|@]|A|$]]|$1|S|3|T|5|D|7|1A|8|@]|9|@]|A|$E|F]]|$1|U|3|V|5|6|7|1B|8|@]|9|@]|A|$]]|$1|W|3|X|5|6|7|1C|8|@]|9|@]|A|$]]|$1|Y|3|Z|5|D|7|1D|8|@]|9|@]|A|$E|F]]|$1|10|3|-4|5|6|7|1E|8|@]|9|@]|A|$]]]|11|$]]

The LocalDate doesn't seem to have this, but WeekFields (which is from the java-8 API) does (<a href="https://docs.oracle.com/javase/8/docs/api/java/time/temporal/WeekFields.html#getFirstDayOfWeek--" rel="nofollow noreferrer">here</a>). So you can do this:

<pre><code>WeekFields.of(Locale.getDefault()).firstDayOfWeek.value
</code></pre>

This returns the value of the first day of week, starting from 1 as Monday, ending with 7 as Sunday.

Example of usage (in Kotlin), to get a new LocalDate that has the dayOfWeek be set, going backward in time instead of forward:

<pre><code>/**@param targetDayOfWeek day of week to go to, starting from 1 as Monday (and 7 is Sunday) */
fun LocalDate.minusDaysToDayOfWeek(targetDayOfWeek: Int = WeekFields.of(Locale.getDefault()).firstDayOfWeek.value): LocalDate {
 //conversion so that Sunday is 0, Monday is 1, etc:
 val diffDays = (dayOfWeek.value % 7) - (targetDayOfWeek % 7)
 val result = when {
 diffDays == 0 -&gt; this
 diffDays &lt; 0 -&gt; minusDays((7 + diffDays).toLong())
 else -&gt; minusDays(diffDays.toLong())
 }
 return result
}
</code></pre>

Example inputs-outputs :

<pre><code>2017-12-31 -&gt; 2017-12-31
2018-01-01 -&gt; 2017-12-31
2018-01-02 -&gt; 2017-12-31
2018-01-03 -&gt; 2017-12-31
2018-01-04 -&gt; 2017-12-31
2018-01-05 -&gt; 2017-12-31
2018-01-06 -&gt; 2017-12-31
2018-01-07 -&gt; 2018-01-07
2018-01-08 -&gt; 2018-01-07
2018-01-09 -&gt; 2018-01-07
2018-01-10 -&gt; 2018-01-07
2018-01-11 -&gt; 2018-01-07
2018-01-12 -&gt; 2018-01-07
2018-01-13 -&gt; 2018-01-07
2018-01-14 -&gt; 2018-01-14
2018-01-15 -&gt; 2018-01-14
</code></pre>

And here's a sample function to go forward in time to the target day of week:

<pre><code>fun LocalDate.plusDaysToDayOfWeek(targetDayOfWeek: Int = getLastDayOfWeek()): LocalDate {
 val diffDays = (targetDayOfWeek % 7) - (dayOfWeek.value % 7)
 val result = when {
 diffDays == 0 -&gt; this
 diffDays &lt; 0 -&gt; plusDays((7 + diffDays).toLong())
 else -&gt; plusDays(diffDays.toLong())
 }
 return result
}

/**@return the last day of week, when 1 is Monday ... 7 is Sunday) */
@JvmStatic
fun getLastDayOfWeek(firstDayOfWeek: DayOfWeek = WeekFields.of(Locale.getDefault()).firstDayOfWeek): Int {
 return when (firstDayOfWeek) {
 DayOfWeek.MONDAY -&gt; DayOfWeek.SUNDAY.value
 else -&gt; firstDayOfWeek.value - 1
 }
}
</code></pre>

BTW, weird thing is that I think the code behind the scenes of the new API actually uses Calendar class anyway...

In case you hate using the dayOfWeek as used for LocalDate (as I do), and you prefer the one used with Calendar, you can use these simple converters:

<pre><code>fun DayOfWeek.toCalendarDayOfWeek(): Int {
 return when (this) {
 DayOfWeek.SATURDAY -&gt; Calendar.SATURDAY
 else -&gt; (this.value + 1) % 7
 }
}

@JvmStatic
fun convertLocalDateDayOfWeekToCalendarDayOfWeek(localDateDayOfWeek: Int): Int {
 return when (localDateDayOfWeek) {
 DayOfWeek.SATURDAY.value -&gt; Calendar.SATURDAY
 else -&gt; (localDateDayOfWeek + 1) % 7
 }
}

@JvmStatic
fun convertFromCalendarDayOfWeekToLocalDateDayOfWeek(calendarDayOfWeek: Int): Int {
 return when (calendarDayOfWeek) {
 Calendar.SUNDAY -&gt; DayOfWeek.SUNDAY.value
 else -&gt; calendarDayOfWeek - 1
 }
}
</code></pre>

blocks|key|142720|text|如果我想在星期一获得作为当前一周的第一天，它对我来说很有效：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|142721|LocalDate+mondayDate+=+LocalDate.now().with(WeekFields.of(Locale.FRANCE).getFirstDayOfWeek());|code-block|syntax|javascript|142722|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

It works for me in case if I want to get Monday as a first day of current week:

<pre><code>LocalDate mondayDate = LocalDate.now().with(WeekFields.of(Locale.FRANCE).getFirstDayOfWeek());
</code></pre>

blocks|key|2926233|text|public+void+getWeekFromADateOfAMonth(){
++++String+date+=+"2019-01-02T18:25:43.511Z";
++++TemporalField+fieldISO+=+WeekFields.of(Locale.US).dayOfWeek();
++++ZonedDateTime+dateTime+=+ZonedDateTime.parse(date);

++++int+week+=+dateTime.get+(+IsoFields.WEEK_OF_WEEK_BASED_YEAR+);
++++int+weekYear+=+dateTime.get+(+IsoFields.WEEK_BASED_YEAR+);

++++System.out.println+(+"now:+"+%2B+dateTime+%2B+"+is+week:+"+%2B+week+%2B+"+of+weekYear:+"+%2B+weekYear+);

++++int+startDate+=+dateTime.with(fieldISO,1).getDayOfMonth();
++++int+endDate+=+dateTime.with(fieldISO,7).getDayOfMonth();

++++String+startMonth+=+String.valueOf(dateTime.with(fieldISO,1).getMonth());
++++String+endMonth+=+String.valueOf(dateTime.with(fieldISO,7).getMonth());
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2926234|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>public void getWeekFromADateOfAMonth(){
 String date = "2019-01-02T18:25:43.511Z";
 TemporalField fieldISO = WeekFields.of(Locale.US).dayOfWeek();
 ZonedDateTime dateTime = ZonedDateTime.parse(date);

 int week = dateTime.get ( IsoFields.WEEK_OF_WEEK_BASED_YEAR );
 int weekYear = dateTime.get ( IsoFields.WEEK_BASED_YEAR );

 System.out.println ( "now: " + dateTime + " is week: " + week + " of weekYear: " + weekYear );

 int startDate = dateTime.with(fieldISO,1).getDayOfMonth();
 int endDate = dateTime.with(fieldISO,7).getDayOfMonth();

 String startMonth = String.valueOf(dateTime.with(fieldISO,1).getMonth());
 String endMonth = String.valueOf(dateTime.with(fieldISO,7).getMonth());
}
</code></pre>

blocks|key|2713660|text|LocalDate.now(+ZoneId.systemDefault()).with(+TemporalAdjusters.previousOrSame(+DayOfWeek.MONDAY+)+);|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2713661|这个返回值是当前周的第一个星期一(如果今天是星期一)|unstyled|2713662|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|J|8|@]|9|@]|A|$]]|$1|G|3|-4|5|F|7|K|8|@]|9|@]|A|$]]]|H|$]]

<pre><code>LocalDate.now( ZoneId.systemDefault()).with( TemporalAdjusters.previousOrSame( DayOfWeek.MONDAY ) );
</code></pre>
This return the first monday of current week (considering if today is monday)

I would like the get the date of the first day of the week based on LocalDate.now(). The following was possible with JodaTime, but seems to be removed from the new Date API in Java 8.

<pre><code>LocalDate now = LocalDate.now();
System.out.println(now.withDayOfWeek(DateTimeConstants.MONDAY));
</code></pre>

I can not call 'withDayOfWeek()', because it does not exist.

So my question is: How to get the date of the first day of the week based on some LocalDate?

Get date of first day of week based on LocalDate.now() in Java 8

Kotlin

Java

我希望根据LocalDate.now()来获取一周的第一天的日期。下面的代码在JodaTime中是可能的，但似乎从Java8中的新Date API中删除了。LocalDate now = LocalDate.now();System.out.println(now.withDayOfWeek(DateTimeConst...

问根据Java8中的LocalDate.now()获取一周的第一天的日期
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