blocks|key|322594|text|您可以使用它，但您必须使用java+API的SimpleDateFormatter将日期值解析为适当的日期格式。您可以指定所需的任何格式。在此之后，您可以进行操作，以获得一年中的第几周。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|322595|entityMap^0|D|8|M|J|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

You can use that, but you have to parse the date value to proper date format using <code>SimpleDateFormatter</code> of <code>java API</code>. You can specify any format you want. After that you can do you manipulation to get the week of the year.

blocks|key|322623|text|您可以将日期存储为字符串，并且用户几乎可以以您指定的任何格式输入日期。您只需要使用DateFormat对象来解释它们输入的日期。例如，请参阅Convert+String+to+Calendar+Object+in+Java上的top+answer。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|322624|Calendar+cal+=+Calendar.getInstance();
SimpleDateFormat+sdf+=+new+SimpleDateFormat("EEE+MMM+dd+HH:mm:ss+z+yyyy");
cal.setTime(sdf.parse("Mon+Mar+14+16:02:37+GMT+2011"));|code-block|syntax|javascript|322625|要从JTextField中读取日期，您可以将其替换为以下内容：|322626|SimpleDateFormat+sdf+=+new+SimpleDateFormat("yyyy-MM-dd");+//+or+any+other+date+format
cal.setTime(sdf.parse(dateTextField.getText()));|322627|然后，您只需以问题中显示的相同方式从cal中读取周数。(这是一个简化的示例。您需要处理DateFormat+parse方法抛出的潜在ParseException。)|322628|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/q/5301226/1288|1|https://stackoverflow.com/a/5301325/1288|2|http://docs.oracle.com/javase/6/docs/api/java/text/DateFormat.html#parse%2528java.lang.String%2529^0|15|A|1Y|15|0|35|A|1|0|0|2|A|0|0|I|3|17|A|1I|5|1U|E|1I|5|2|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@$9|15|A|16|1|17]|$9|18|A|19|1|1A]]|E|$]]|$1|F|3|G|5|H|7|1B|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|1C|8|@$9|1D|A|1E|B|C]]|D|@]|E|$]]|$1|M|3|N|5|H|7|1F|8|@]|D|@]|E|$I|J]]|$1|O|3|P|5|6|7|1G|8|@$9|1H|A|1I|B|C]|$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]|$9|1N|A|1O|B|C]]|D|@$9|1P|A|1Q|1|1R]]|E|$]]|$1|Q|3|-4|5|6|7|1S|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|X]]|Y|$5|T|U|V|E|$W|Z]]|10|$5|T|U|V|E|$W|11]]]]

You can store the date as a String, and the user can enter it in pretty much any format you specify. You just need to use a <code>DateFormat</code> object to interpret the date that they enter. For example, see the <a href="https://stackoverflow.com/a/5301325/1288">top answer</a> on <a href="https://stackoverflow.com/q/5301226/1288">Convert String to Calendar Object in Java</a>.

<pre><code>Calendar cal = Calendar.getInstance();
SimpleDateFormat sdf = new SimpleDateFormat("EEE MMM dd HH:mm:ss z yyyy");
cal.setTime(sdf.parse("Mon Mar 14 16:02:37 GMT 2011"));
</code></pre>

To read the date from a <code>JTextField</code>, you could replace that with something like:

<pre><code>SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); // or any other date format
cal.setTime(sdf.parse(dateTextField.getText()));
</code></pre>

Then you just need to read the week number from <code>cal</code> in the same way you showed in the question. (This is a simplified example. You'd need to handle the potential <code>ParseException</code> thrown by the <code>DateFormat</code> <a href="http://docs.oracle.com/javase/6/docs/api/java/text/DateFormat.html#parse%28java.lang.String%29" rel="nofollow noreferrer"><code>parse</code></a> method.)

blocks|key|322653|text|public+static+int+getWeek()+{
++++++++return+Calendar.getInstance().get(Calendar.WEEK_OF_YEAR);
++++}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|322654|工作正常，当前实时返回一周|unstyled|322655|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>public static int getWeek() {
 return Calendar.getInstance().get(Calendar.WEEK_OF_YEAR);
 }
</code></pre>

Works fine and return week for current realtime

blocks|key|105577|text|Java1.8在java.time包中为您提供了一些新类|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|105578|import+java.time.Instant;
import+java.time.ZoneId;
import+java.time.ZonedDateTime;
import+java.time.temporal.IsoFields;

ZonedDateTime+now+=+ZonedDateTime.ofInstant(Instant.now(),+ZoneId.systemDefault());
System.out.printf("Week+%25d%25n",+now.get(IsoFields.WEEK_OF_WEEK_BASED_YEAR));|code-block|syntax|javascript|105579|大多数遗留日历都可以很容易地通过互操作性方法转换为java.time.ZonedDateTime+/+java.time.Instant，在您的特定情况下是GregorianCalendar.toZonedDateTime()。|105580|entityMap^0|8|9|0|0|P|N|1F|H|26|Z|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|M|3|-4|5|6|7|Z|8|@]|D|@]|E|$]]]|N|$]]

Java 1.8 provides you with some new classes in package <code>java.time</code>:

<pre><code>import java.time.Instant;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.temporal.IsoFields;

ZonedDateTime now = ZonedDateTime.ofInstant(Instant.now(), ZoneId.systemDefault());
System.out.printf("Week %d%n", now.get(IsoFields.WEEK_OF_WEEK_BASED_YEAR));
</code></pre>

Most legacy calendars can easily be converted to <code>java.time.ZonedDateTime</code> / <code>java.time.Instant</code> by interoperability methods, in your particular case <code>GregorianCalendar.toZonedDateTime()</code>.

blocks|key|105597|text|这个很适合我|type|unstyled|depth|inlineStyleRanges|entityRanges|data|105598|public+void+sortListItems(List<PostModel>+list)+{
++++Collections.sort(list,+new+Comparator<PostModel>()+{
++++++++DateFormat+dateFormat+=+new+SimpleDateFormat("dd/MM/yyyy+HH:mm:ss");
++++++++@Override
++++++++public+int+compare(PostModel+o1,+PostModel+o2)+{
++++++++++++int+ret+=+0;
++++++++++++try+{
++++++++++++++++ret+=+dateFormat.parse(o1.getDate()).compareTo(dateFormat.parse(o2.getDate()));
++++++++++++++++return+ret;
++++++++++++}+catch+(ParseException+e)+{
++++++++++++++++e.printStackTrace();
++++++++++++}

++++++++++++return+ret;
++++++++}
++++});
}|code-block|syntax|javascript|105599|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|$]]

this one worked for me

<pre><code>public void sortListItems(List&lt;PostModel&gt; list) {
 Collections.sort(list, new Comparator&lt;PostModel&gt;() {
 DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy HH:mm:ss");
 @Override
 public int compare(PostModel o1, PostModel o2) {
 int ret = 0;
 try {
 ret = dateFormat.parse(o1.getDate()).compareTo(dateFormat.parse(o2.getDate()));
 return ret;
 } catch (ParseException e) {
 e.printStackTrace();
 }

 return ret;
 }
 });
}
</code></pre>

blocks|key|105619|text|WeekFields|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|105620|我使用WeekFields、DateTimeFormatter、LocalDate和TemporalField创建的这个方法适用于Java8和更高版本。|105621|别忘了根据你的用例适当地格式化你的日期！|105622|public+int+getWeekNum(String+input)+{
++++DateTimeFormatter+formatter+=+DateTimeFormatter.ofPattern("M/dd/yy");+++//+Define+formatting+pattern+to+match+your+input+string.
++++LocalDate+date+=+LocalDate.parse(input,+formatter);+++++++++++++++++++++//+Parse+string+into+a+`LocalDate`+object.

++++WeekFields+wf+=+WeekFields.of(Locale.getDefault())+;++++++++++++++++++++//+Use+week+fields+appropriate+to+your+locale.+People+in+different+places+define+a+week+and+week-number+differently,+such+as+starting+on+a+Monday+or+a+Sunday,+and+so+on.
++++TemporalField+weekNum+=+wf.weekOfWeekBasedYear();+++++++++++++++++++++++//+Represent+the+idea+of+this+locale’s+definition+of+week+number+as+a+`TemporalField`.+
++++int+week+=+Integer.parseInt(String.format("%2502d",date.get(weekNum)));+++//+Using+that+locale’s+definition+of+week+number,+determine+the+week-number+for+this+particular+`LocalDate`+value.

++++return+week;
}|code-block|syntax|javascript|105623|entityMap|0|LINK|mutability|MUTABLE|url|https://docs.oracle.com/javase/9/docs/api/java/time/temporal/WeekFields.html|1|https://docs.oracle.com/javase/9/docs/api/java/time/format/DateTimeFormatter.html|2|https://docs.oracle.com/javase/9/docs/api/java/time/LocalDate.html|3|https://docs.oracle.com/javase/9/docs/api/java/time/temporal/TemporalField.html^0|0|A|0|3|A|E|H|W|9|16|D|3|A|0|E|H|1|W|9|2|16|D|3|0|0|0^^$0|@$1|2|3|4|5|6|7|12|8|@$9|13|A|14|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|15|8|@$9|16|A|17|B|C]|$9|18|A|19|B|C]|$9|1A|A|1B|B|C]|$9|1C|A|1D|B|C]]|D|@$9|1E|A|1F|1|1G]|$9|1H|A|1I|1|1J]|$9|1K|A|1L|1|1M]|$9|1N|A|1O|1|1P]]|E|$]]|$1|H|3|I|5|6|7|1Q|8|@]|D|@]|E|$]]|$1|J|3|K|5|L|7|1R|8|@]|D|@]|E|$M|N]]|$1|O|3|-4|5|6|7|1S|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]|W|$5|R|S|T|E|$U|X]]|Y|$5|R|S|T|E|$U|Z]]|10|$5|R|S|T|E|$U|11]]]]

<h1><code>WeekFields</code></h1>

This method that I created works for me in Java 8 and later, using <a href="https://docs.oracle.com/javase/9/docs/api/java/time/temporal/WeekFields.html" rel="nofollow noreferrer"><code>WeekFields</code></a>, <a href="https://docs.oracle.com/javase/9/docs/api/java/time/format/DateTimeFormatter.html" rel="nofollow noreferrer"><code>DateTimeFormatter</code></a>, <a href="https://docs.oracle.com/javase/9/docs/api/java/time/LocalDate.html" rel="nofollow noreferrer"><code>LocalDate</code></a>, and <a href="https://docs.oracle.com/javase/9/docs/api/java/time/temporal/TemporalField.html" rel="nofollow noreferrer"><code>TemporalField</code></a>. 

Don't forget to format your date properly based on your use case! 

<pre><code>public int getWeekNum(String input) {
 DateTimeFormatter formatter = DateTimeFormatter.ofPattern("M/dd/yy"); // Define formatting pattern to match your input string.
 LocalDate date = LocalDate.parse(input, formatter); // Parse string into a `LocalDate` object.

 WeekFields wf = WeekFields.of(Locale.getDefault()) ; // Use week fields appropriate to your locale. People in different places define a week and week-number differently, such as starting on a Monday or a Sunday, and so on.
 TemporalField weekNum = wf.weekOfWeekBasedYear(); // Represent the idea of this locale’s definition of week number as a `TemporalField`. 
 int week = Integer.parseInt(String.format("%02d",date.get(weekNum))); // Using that locale’s definition of week number, determine the week-number for this particular `LocalDate` value.

 return week;
}
</code></pre>

I have a small program that displays the current week from todays date, like this:

<pre><code>GregorianCalendar gc = new GregorianCalendar();
int day = 0;
gc.add(Calendar.DATE, day);
</code></pre>

And then a JLabel that displays the week number:

<pre><code>JLabel week = new JLabel("Week " + gc.get(Calendar.WEEK_OF_YEAR));
</code></pre>

So right now I'd like to have a JTextField where you can enter a date and the JLabel will update with the week number of that date. I'm really not sure how to do this as I'm quite new to Java. Do I need to save the input as a String? An integer? And what format would it have to be (yyyyMMdd etc)? If anyone could help me out I'd appreciate it!

Java: Get week number from any date?

我有一个小程序，它显示从今天开始的当前星期，如下所示：GregorianCalendar gc = new GregorianCalendar();int day = 0;gc.add(Calendar.DATE, day);然后是一个显示周数字的JLabel：JLabel week = new JLabel("Wee...

问Java:从任何日期获取周数？
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