有用なコメントに従って、日付フォーマッタを完全に再構築しました。使用法は次のとおりです。
- 短くする（ワンライナー）
- 使い捨てオブジェクト (タイムゾーン、フォーマット) を文字列として表現する
- 便利で並べ替え可能な ISO 形式とレガシー形式を最初からサポート
このコードが役立つと思われる場合は、ソースと JAR を github で公開することがあります。
使用法
// The problem - not UTC
Date.toString()
"Tue Jul 03 14:54:24 IDT 2012"
// ISO format, now
PrettyDate.now()
"2012-07-03T11:54:24.256 UTC"
// ISO format, specific date
PrettyDate.toString(new Date())
"2012-07-03T11:54:24.256 UTC"
// Legacy format, specific date
PrettyDate.toLegacyString(new Date())
"Tue Jul 03 11:54:24 UTC 2012"
// ISO, specific date and time zone
PrettyDate.toString(moonLandingDate, "yyyy-MM-dd hh:mm:ss zzz", "CST")
"1969-07-20 03:17:40 CDT"
// Specific format and date
PrettyDate.toString(moonLandingDate, "yyyy-MM-dd")
"1969-07-20"
// ISO, specific date
PrettyDate.toString(moonLandingDate)
"1969-07-20T20:17:40.234 UTC"
// Legacy, specific date
PrettyDate.toLegacyString(moonLandingDate)
"Wed Jul 20 08:17:40 UTC 1969"
コード
(このコードはCode Review stackexchange に関する質問の対象でもあります)
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;
/**
* Formats dates to sortable UTC strings in compliance with ISO-8601.
*
* @author Adam Matan <adam@matan.name>
* @see http://stackoverflow.com/questions/11294307/convert-java-date-to-utc-string/11294308
*/
public class PrettyDate {
public static String ISO_FORMAT = "yyyy-MM-dd'T'HH:mm:ss.SSS zzz";
public static String LEGACY_FORMAT = "EEE MMM dd hh:mm:ss zzz yyyy";
private static final TimeZone utc = TimeZone.getTimeZone("UTC");
private static final SimpleDateFormat legacyFormatter = new SimpleDateFormat(LEGACY_FORMAT);
private static final SimpleDateFormat isoFormatter = new SimpleDateFormat(ISO_FORMAT);
static {
legacyFormatter.setTimeZone(utc);
isoFormatter.setTimeZone(utc);
}
/**
* Formats the current time in a sortable ISO-8601 UTC format.
*
* @return Current time in ISO-8601 format, e.g. :
* "2012-07-03T07:59:09.206 UTC"
*/
public static String now() {
return PrettyDate.toString(new Date());
}
/**
* Formats a given date in a sortable ISO-8601 UTC format.
*
* <pre>
* <code>
* final Calendar moonLandingCalendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
* moonLandingCalendar.set(1969, 7, 20, 20, 18, 0);
* final Date moonLandingDate = moonLandingCalendar.getTime();
* System.out.println("UTCDate.toString moon: " + PrettyDate.toString(moonLandingDate));
* >>> UTCDate.toString moon: 1969-08-20T20:18:00.209 UTC
* </code>
* </pre>
*
* @param date
* Valid Date object.
* @return The given date in ISO-8601 format.
*
*/
public static String toString(final Date date) {
return isoFormatter.format(date);
}
/**
* Formats a given date in the standard Java Date.toString(), using UTC
* instead of locale time zone.
*
* <pre>
* <code>
* System.out.println(UTCDate.toLegacyString(new Date()));
* >>> "Tue Jul 03 07:33:57 UTC 2012"
* </code>
* </pre>
*
* @param date
* Valid Date object.
* @return The given date in Legacy Date.toString() format, e.g.
* "Tue Jul 03 09:34:17 IDT 2012"
*/
public static String toLegacyString(final Date date) {
return legacyFormatter.format(date);
}
/**
* Formats a date in any given format at UTC.
*
* <pre>
* <code>
* final Calendar moonLandingCalendar = Calendar.getInstance(TimeZone.getTimeZone("UTC"));
* moonLandingCalendar.set(1969, 7, 20, 20, 17, 40);
* final Date moonLandingDate = moonLandingCalendar.getTime();
* PrettyDate.toString(moonLandingDate, "yyyy-MM-dd")
* >>> "1969-08-20"
* </code>
* </pre>
*
*
* @param date
* Valid Date object.
* @param format
* String representation of the format, e.g. "yyyy-MM-dd"
* @return The given date formatted in the given format.
*/
public static String toString(final Date date, final String format) {
return toString(date, format, "UTC");
}
/**
* Formats a date at any given format String, at any given Timezone String.
*
*
* @param date
* Valid Date object
* @param format
* String representation of the format, e.g. "yyyy-MM-dd HH:mm"
* @param timezone
* String representation of the time zone, e.g. "CST"
* @return The formatted date in the given time zone.
*/
public static String toString(final Date date, final String format, final String timezone) {
final TimeZone tz = TimeZone.getTimeZone(timezone);
final SimpleDateFormat formatter = new SimpleDateFormat(format);
formatter.setTimeZone(tz);
return formatter.format(date);
}
}