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POHow to strictly parse a date with only a year and a week number when the first day of this week is in the previous year?
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  1. POHow to strictly parse a date with only a year and a week number when the first day of this week is in the previous year?
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    copied!<p>My goal is to have a strict parsing (and forbid dates like '98/99' for example). However, the following code raises a <code>java.text.ParseException</code> with the message <em>Unparseable date: "98/01"</em>:</p> <pre><code>SimpleDateFormat sdf = new SimpleDateFormat("yy/ww"); sdf.setLenient(false); sdf.parse("98/01"); </code></pre> <p>This is indeed for the <a href="http://www.timeanddate.com/calendar/monthly.html?year=1998&amp;month=1&amp;country=5" rel="nofollow">first week of 1998</a>, which starts on a Thursday. However, the parsing of a week always returns the date of the <strong>first day</strong> of this week. In that case, it would be <em>12/29/1997</em>. And this is why an exception is raised.</p> <p>It seems this problem comes from the <code>GregorianCalendar</code> class and more specifically from the <code>computeTime()</code> method which checks if the original fields match the fields externally set when the parsing is <strong>not lenient</strong>:</p> <pre><code>if (!isLenient()) { for (int field = 0; field &lt; FIELD_COUNT; field++) { if (!isExternallySet(field)) { continue; } if (originalFields[field] != internalGet(field)) { // Restore the original field values System.arraycopy(originalFields, 0, fields, 0, fields.length); throw new IllegalArgumentException(getFieldName(field)); } } } </code></pre> <p>Is this a bug? I think parsing <em>1998/01</em> should indeed return <em>12/29/1997</em> and not raise any exception. However, do you know how to make the parsing returns <em>01/01/1998</em> instead (which would be the first day of the week in the specified year)?</p>
 

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