！JAVA学习提高之－－－－ JAVA日期格式化及相关操作

http://blog.csdn.net/gubaohua/archive/2005/07/29/439506.aspx
http://icansoft.blog.51cto.com/268543/50000
http://topic.csdn.net/t/20050727/12/4171134.html
http://brucezheng.iteye.com/blog/86967
http://www.blogjava.net/ruoyoux/archive/2008/10/26/236711.html

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
public abstract class DateHelper {
	public static final int YEAR = Calendar.YEAR;
	public static final int MONTH = Calendar.MONTH;
	public static final int DATE = Calendar.DATE;
	public static final int HOUR = Calendar.HOUR;
	public static final int HOUR24 = Calendar.HOUR_OF_DAY;
	public static final int MINUTE = Calendar.MINUTE;
	public static final int SECOND = Calendar.SECOND;
	public static final int DAY_OF_WEEK = Calendar.DAY_OF_WEEK;
	public static final int WEEK_OF_YEAR = Calendar.WEEK_OF_YEAR;
	public static final long millisInDay = 86400000;
	private static final SimpleDateFormat mFormat6chars = new SimpleDateFormat(
			"yyMMdd");
	private static final SimpleDateFormat mFormat8chars = new SimpleDateFormat(
			"yyyyMMdd");
	private static final SimpleDateFormat mFormatIso8601Day = new SimpleDateFormat(
			"yyyy-MM-dd");
	private static final SimpleDateFormat mFormatIso8601 = new SimpleDateFormat(
			"yyyy-MM-dd HH:mm:ss");
	// http://www.w3.org/Protocols/rfc822/Overview.html#z28
	private static final SimpleDateFormat mFormatRfc822 = new SimpleDateFormat(
			"EEE, d MMM yyyy HH:mm:ss z");
	// -----------------------------------------------------------------------
	/**
	 * Returns a Date set to the last possible millisecond of the day, just
	 * before midnight. If a null day is passed in, a new Date is created.
	 * midnight (00m 00h 00s)
	 */
	public static Date getEndOfDay(Date day) {
		if (day == null)
			day = new Date();
		Calendar cal = Calendar.getInstance();
		cal.setTime(day);
		cal.set(Calendar.HOUR_OF_DAY, cal.getMaximum(Calendar.HOUR_OF_DAY));
		cal.set(Calendar.MINUTE, cal.getMaximum(Calendar.MINUTE));
		cal.set(Calendar.SECOND, cal.getMaximum(Calendar.SECOND));
		cal.set(Calendar.MILLISECOND, cal.getMaximum(Calendar.MILLISECOND));
		return cal.getTime();
	}
	/**
	 * Returns a Date set to the first possible millisecond of the day, just
	 * after midnight. If a null day is passed in, a new Date is created.
	 * midnight (00m 00h 00s)
	 */
	public static Date getStartOfDay(Date day) {
		if (day == null)
			day = new Date();
		Calendar cal = Calendar.getInstance();
		cal.setTime(day);
		cal.set(Calendar.HOUR_OF_DAY, cal.getMinimum(Calendar.HOUR_OF_DAY));
		cal.set(Calendar.MINUTE, cal.getMinimum(Calendar.MINUTE));
		cal.set(Calendar.SECOND, cal.getMinimum(Calendar.SECOND));
		cal.set(Calendar.MILLISECOND, cal.getMinimum(Calendar.MILLISECOND));
		return cal.getTime();
	}
	/**
	 * Returns a Date set just to Noon, to the closest possible millisecond of
	 * the day. If a null day is passed in, a new Date is created. nnoon (00m
	 * 12h 00s)
	 */
	public static Date getNoonOfDay(Date day) {
		if (day == null)
			day = new Date();
		Calendar cal = Calendar.getInstance();
		cal.setTime(day);
		cal.set(Calendar.HOUR_OF_DAY, 12);
		cal.set(Calendar.MINUTE, cal.getMinimum(Calendar.MINUTE));
		cal.set(Calendar.SECOND, cal.getMinimum(Calendar.SECOND));
		cal.set(Calendar.MILLISECOND, cal.getMinimum(Calendar.MILLISECOND));
		return cal.getTime();
	}
	// -----------------------------------------------------------------------
	/**
	 * Returns a string the represents the passed-in date parsed according to
	 * the passed-in format. Returns an empty string if the date or the format
	 * is null.
	 */
	public static String format(Object dateStr, SimpleDateFormat format) {
		if (dateStr == null || format == null) {
			return "";
		}
		return format.format(dateStr);
	}
	// -----------------------------------------------------------------------
	/**
	 * Returns a Date using the passed-in string and format. Returns null if the
	 * string is null or empty or if the format is null. The string must match
	 * the format.
	 */
	public static Date parse(String dateValue, SimpleDateFormat aFormat)
			throws ParseException {
		if (StringHelper.isEmpty(dateValue) || aFormat == null) {
			return null;
		}
		return aFormat.parse(dateValue);
	}
	public static Date parse(String dateValue, String formatStr)
			throws ParseException {
		if (StringHelper.isEmpty(dateValue) || formatStr == null) {
			return null;
		}
		return new SimpleDateFormat(formatStr).parse(dateValue);
	}
	// -----------------------------------------------------------------------
	/**
	 * Returns true if endDate is after startDate or if startDate equals endDate
	 * or if they are the same date. Returns false if either value is null.
	 */
	public static boolean isValidDateRange(Date startDate, Date endDate) {
		return isValidDateRange(startDate, endDate, true);
	}
	// -----------------------------------------------------------------------
	/**
	 * Returns true if endDate is after startDate or if startDate equals
	 * endDate. Returns false if either value is null. If equalOK, returns true
	 * if the dates are equal.
	 */
	public static boolean isValidDateRange(Date startDate, Date endDate,
			boolean equalOK) {
		// false if either value is null
		if (startDate == null || endDate == null) {
			return false;
		}
		if (equalOK) {
			// true if they are equal
			if (startDate.equals(endDate)) {
				return true;
			}
		}
		// true if endDate after startDate
		if (endDate.after(startDate)) {
			return true;
		}
		return false;
	}
	// -----------------------------------------------------------------------
	// convenience method returns long friendly formatted timestamp
	public static String format6chars(Object date) {
		return DateHelper.format(date, mFormat6chars);
	}
	// -----------------------------------------------------------------------
	// convenience method returns long friendly formatted timestamp
	public static String format8chars(Object date) {
		return DateHelper.format(date, mFormat8chars);
	}
	// -----------------------------------------------------------------------
	// convenience method returns long friendly formatted timestamp
	public static String formatIso8601Day(Object date) {
		return DateHelper.format(date, mFormatIso8601Day);
	}
	// -----------------------------------------------------------------------
	public static String formatRfc822(Object date) {
		return DateHelper.format(date, mFormatRfc822);
	}
	// -----------------------------------------------------------------------
	// This is a hack, but it seems to work
	public static String formatIso8601(Object date) {
		if (date == null)
			return "";
		// Add a colon 2 chars before the end of the string
		// to make it a valid ISO-8601 date.
		String str = DateHelper.format(date, mFormatIso8601);
		// StringBuffer sb = new StringBuffer();
		// sb.append(str.substring(0, str.length() - 2));
		// sb.append(":");
		// sb.append(str.substring(str.length() - 2));
		// return sb.toString();
		return str;
	}
	public static Date getDate() {
		return new Date();
	}
	public static Date getDate(long date) {
		return new Date(date);
	}
	public static long getTime() {
		return new Date().getTime();
	}
	public static long getTime(Date date) {
		return date.getTime();
	}
	public static long getTime(String dateStr, String format)
			throws ParseException {
		SimpleDateFormat sdf = new SimpleDateFormat(format);
		Date date = sdf.parse(dateStr);
		return getTime(date);
	}
	public static long getTime(String dateStr) throws ParseException {
		return getTime(DateHelper.parse(dateStr, DateHelper.mFormatIso8601Day));
	}
	public static String format(long time, String formatStr) {
		if (time == 0)
			return "";
		SimpleDateFormat df = new SimpleDateFormat(formatStr);
		Date date = new Date(time);
		return df.format(date);
	}
	public static String format(Object date, String formatStr) {
		if (date == null)
			return "";
		SimpleDateFormat df = new SimpleDateFormat(formatStr);
		return df.format(date);
	}
	public static String format(long time) {
		return DateHelper.formatIso8601Day(new Date(time));
	}
	public static String format(Date time, String formatStr)
			throws ParseException {
		if (time == null)
			return "";
		long longTime = Long.parseLong(time.toString());
		if (longTime == 0)
			return "";
		SimpleDateFormat sdf = new SimpleDateFormat(formatStr);
		Date date = new Date(longTime);
		return sdf.format(date);
	}
	public static String format(Long time) throws ParseException {
		return DateHelper.format(time.longValue());
	}
	public static String format(Date date) {
		return DateHelper.formatIso8601Day(date);
	}
	public static String today() {
		return DateHelper.format(new Date());
	}
	public static String today(String formatStr) throws ParseException {
		return DateHelper.format(getTime(today()), formatStr);
	}
	public static String now() {
		return DateHelper.formatRfc822(new Date());
	}
	public static String now(String formatStr) throws ParseException {
		SimpleDateFormat sdf = new SimpleDateFormat(formatStr);
		return sdf.format(new Date());
	}
	
	public static int get(int field) {
		GregorianCalendar calendar = new GregorianCalendar();
		int reValue = 0;
		switch (field) {
		case YEAR:
			reValue = calendar.get(YEAR);
			break;
		case MONTH:
			reValue = calendar.get(MONTH) + 1;
			break;
		case DATE:
			reValue = calendar.get(DATE);
			break;
		case HOUR:
			reValue = calendar.get(HOUR);
			break;
		case HOUR24:
			reValue = calendar.get(HOUR24);
			break;
		case MINUTE:
			reValue = calendar.get(MINUTE);
			break;
		case SECOND:
			reValue = calendar.get(SECOND);
			break;
		case DAY_OF_WEEK:
			reValue = calendar.get(DAY_OF_WEEK);
			break;
		case WEEK_OF_YEAR:
			reValue = calendar.get(WEEK_OF_YEAR);
			break;
		default:
			reValue = 0;
		}
		return reValue;
	}
	public static int get(int field,Date date) {
		GregorianCalendar calendar = new GregorianCalendar();
		calendar.setTime(date);
		int reValue = 0;
		switch (field) {
		case YEAR:
			reValue = calendar.get(YEAR);
			break;
		case MONTH:
			reValue = calendar.get(MONTH) + 1;
			break;
		case DATE:
			reValue = calendar.get(DATE);
			break;
		case HOUR:
			reValue = calendar.get(HOUR);
			break;
		case HOUR24:
			reValue = calendar.get(HOUR24);
			break;
		case MINUTE:
			reValue = calendar.get(MINUTE);
			break;
		case SECOND:
			reValue = calendar.get(SECOND);
			break;
		case DAY_OF_WEEK:
			reValue = calendar.get(DAY_OF_WEEK);
			break;
		case WEEK_OF_YEAR:
			reValue = calendar.get(WEEK_OF_YEAR);
			break;
		default:
			reValue = 0;
		}
		return reValue;
	}
	public static void main(String[] args) throws Exception {
		System.out.println(DateHelper.getNoonOfDay(new Date()));
		System.out.println(format(DateHelper.getTime("2001-09-02 12:56")));
		System.out.println(DateHelper.get(DateHelper.YEAR));
		System.out.println(DateHelper.get(DateHelper.MONTH));
		System.out.println(DateHelper.get(DateHelper.DATE));
	}
}