Java日期类型的解析

从字符串解析出JAVA日期类型java.util.Date是一件相当痛苦的事情，下面就列出了一些被大量使用了的格式，可谓大观：

标准/说明	示例
valid RFC 822 (2-digit year)	Thu, 01 Jan 04 19:48:21 GMT
valid RFC 822 (4-digit year)	Thu, 01 Jan 2004 19:48:21 GMT
invalid RFC 822 (no time)	01 Jan 2004
invalid RFC 822 (no seconds)	01 Jan 2004 00:00 GMT
valid W3CDTF (numeric timezone)	2003-12-31T10:14:55-08:00
valid W3CDTF (UTC timezone)	2003-12-31T10:14:55Z
valid W3CDTF (yyyy)	2003
valid W3CDTF (yyyy-mm)	2003-12
valid W3CDTF (yyyy-mm-dd)	2003-12-31
valid ISO 8601 (yyyymmdd)	20031231
valid ISO 8601 (-yy-mm)	-03-12
valid ISO 8601 (-yymm)	-0312
valid ISO 8601 (-yy-mm-dd)	-03-12-31
valid ISO 8601 (yymmdd)	031231
valid ISO 8601 (yyyy-o)	2003-335
valid ISO 8601 (yyo)	03335
valid asctime	Sun Jan 4 16:29:06 PST 2004
bogus RFC 822 (invalid day/month)	Thu, 31 Jun 2004 19:48:21 GMT
bogus RFC 822 (invalid month)	Mon, 26 January 2004 16:31:00 EST
bogus RFC 822 (invalid timezone)	Mon, 26 Jan 2004 16:31:00 ET
bogus W3CDTF (invalid hour)	2003-12-31T25:14:55Z
bogus W3CDTF (invalid minute)	2003-12-31T10:61:55Z
bogus W3CDTF (invalid second)	2003-12-31T10:14:61Z
bogus (MSSQL)	2004-07-08 23:56:58.0
bogus (MSSQL-ish, without fractional second)	2004-07-08 23:56:58
bogus (Korean)	2004-05-25 ? 11:23:17
bogus (Greek)	Κυρ, 11 Ιο?λ 2004 12:00:00 EST
bogus (Hungarian)	július-13T9:15-05:00

JodaTime虽然号称时下最流行的java date工具，但是对于这个问题也是爱莫能助，只能乖乖地进行格式匹配了。

为了不重复制造轮子，我从rssowl项目[http://www.rssowl.org/]中抽取了它的日期时间解析工具类，供各位童鞋参考：

import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Locale;
import java.util.TimeZone;

/**
 * Utility Class for working with <code>Dates</code>.
 * 
 * @author bpasero
 * modified by http://joeblow.iteye.com
 * 2010-11-11
 */
public class DateUtils {

	/** 1 Day in Millis */
	public static final long DAY = 24L * 60L * 60L * 1000L;

	/** 1 Week in Millis */
	public static final long WEEK = 7 * DAY;

	/* An array of custom date formats */
	private static final DateFormat[] CUSTOM_DATE_FORMATS;

	/* The Default Timezone to be used */
	private static final TimeZone TIMEZONE = TimeZone.getTimeZone("UTC"); //$NON-NLS-1$

	/**
	 * Tries different date formats to parse against the given string
	 * representation to retrieve a valid Date object.
	 * 
	 * @param strdate
	 *            Date as String
	 * @return Date The parsed Date
	 */
	public static Date parseDate(String strdate) {

		/* Return in case the string date is not set */
		if (strdate == null || strdate.length() == 0) return null;

		Date result = null;
		strdate = strdate.trim();
		if (strdate.length() > 10) {

			/* Open: deal with +4:00 (no zero before hour) */
			if ((strdate.substring(strdate.length() - 5).indexOf("+") == 0 || strdate.substring(strdate.length() - 5).indexOf("-") == 0) && strdate.substring(strdate.length() - 5).indexOf(":") == 2) { //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
				String sign = strdate.substring(strdate.length() - 5, strdate.length() - 4);
				strdate = strdate.substring(0, strdate.length() - 5) + sign + "0" + strdate.substring(strdate.length() - 4); //$NON-NLS-1$
			}

			String dateEnd = strdate.substring(strdate.length() - 6);

			/*
			 * try to deal with -05:00 or +02:00 at end of date replace with -0500 or
			 * +0200
			 */
			if ((dateEnd.indexOf("-") == 0 || dateEnd.indexOf("+") == 0) && dateEnd.indexOf(":") == 3) { //$NON-NLS-1$//$NON-NLS-2$ //$NON-NLS-3$
				if (!"GMT".equals(strdate.substring(strdate.length() - 9, strdate.length() - 6))) { //$NON-NLS-1$
					String oldDate = strdate;
					String newEnd = dateEnd.substring(0, 3) + dateEnd.substring(4);
					strdate = oldDate.substring(0, oldDate.length() - 6) + newEnd;
				}
			}
		}

		/* Try to parse the date */
		int i = 0;
		while (i < CUSTOM_DATE_FORMATS.length) {
			try {

				/*
				 * This Block needs to be synchronized, because the parse-Method in
				 * SimpleDateFormat is not Thread-Safe.
				 */
				synchronized (CUSTOM_DATE_FORMATS[i]) {
					return CUSTOM_DATE_FORMATS[i].parse(strdate);
				}
			} catch (ParseException e) {
				i++;
			} catch (NumberFormatException e) {
				i++;
			}
		}
		return result;
	}

	/** Initialize the array of common date formats and formatter */
	static {

		/* Create Date Formats */
		final String[] possibleDateFormats = { 
				/* RFC 1123 with 2-digit Year */"EEE, dd MMM yy HH:mm:ss z", 
				/* RFC 1123 with 4-digit Year */"EEE, dd MMM yyyy HH:mm:ss z", 
				/* RFC 1123 with no Timezone */"EEE, dd MMM yy HH:mm:ss", 
				/* Variant of RFC 1123 */"EEE, MMM dd yy HH:mm:ss", 
				/* RFC 1123 with no Seconds */"EEE, dd MMM yy HH:mm z", 
				/* Variant of RFC 1123 */"EEE dd MMM yyyy HH:mm:ss", 
				/* RFC 1123 with no Day */"dd MMM yy HH:mm:ss z", 
				/* RFC 1123 with no Day or Seconds */"dd MMM yy HH:mm z", 
				/* ISO 8601 slightly modified */"yyyy-MM-dd'T'HH:mm:ssZ", 
				/* ISO 8601 slightly modified */"yyyy-MM-dd'T'HH:mm:ss'Z'", 
				/* ISO 8601 slightly modified */"yyyy-MM-dd'T'HH:mm:sszzzz", 
				/* ISO 8601 slightly modified */"yyyy-MM-dd'T'HH:mm:ss z", 
				/* ISO 8601 */"yyyy-MM-dd'T'HH:mm:ssz", 
				/* ISO 8601 slightly modified */"yyyy-MM-dd'T'HH:mm:ss.SSSz", 
				/* ISO 8601 slightly modified */"yyyy-MM-dd'T'HHmmss.SSSz", 
				/* ISO 8601 slightly modified */"yyyy-MM-dd'T'HH:mm:ss", 
				/* ISO 8601 w/o seconds */"yyyy-MM-dd'T'HH:mmZ", 
				/* ISO 8601 w/o seconds */"yyyy-MM-dd'T'HH:mm'Z'", 
				/* RFC 1123 without Day Name */"dd MMM yyyy HH:mm:ss z", 
				/* RFC 1123 without Day Name and Seconds */"dd MMM yyyy HH:mm z", 
				/* Simple Date Format */"yyyy-MM-dd", 
				/* Simple Date Format */"MMM dd, yyyy" };

		/* Create the dateformats */
		CUSTOM_DATE_FORMATS = new SimpleDateFormat[possibleDateFormats.length];

		for (int i = 0; i < possibleDateFormats.length; i++) {
			CUSTOM_DATE_FORMATS[i] = new SimpleDateFormat(possibleDateFormats[i], Locale.ENGLISH);
			CUSTOM_DATE_FORMATS[i].setTimeZone(TIMEZONE);
		}
	}
}

调用方法：

Date d = DateUtils.parseDate("Tue, 9 Nov 2010 12:45:00 GMT");

PS:11.11真是个有纪念意义的日子啊