content: /*
   * All content copyright Terracotta, Inc., unless otherwise indicated. All rights reserved.
   *
   * Licensed under the Apache License, Version 2.0 (the "License"); you may not
   * use this file except in compliance with the License. You may obtain a copy
   * of the License at
   *
   *   http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
   * License for the specific language governing permissions and limitations
   * under the License.
   *
   */
  
  package com.xxl.job.admin.core.cron;
  
  import java.io.Serializable;
  import java.text.ParseException;
  import java.util.*;
  
  /**
   * Provides a parser and evaluator for unix-like cron expressions. Cron expressions
   * provide the ability to specify complex time combinations such as &quot;At 8:00am every
   * Monday through Friday&quot; or &quot;At 1:30am every last Friday of the month&quot;.
   * <P>
   * Cron expressions are comprised of 6 required fields and one optional field separated by
   * white space. The fields respectively are described as follows:
   *
   * <table cellspacing="8">
   * <tr>
   * <th align="left">Field Name</th>
   * <th align="left">&nbsp;</th>
   * <th align="left">Allowed Values</th>
   * <th align="left">&nbsp;</th>
   * <th align="left">Allowed Special Characters</th>
   * </tr>
   * <tr>
   * <td align="left"><code>Seconds</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>0-59</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>, - * /</code></td>
   * </tr>
   * <tr>
   * <td align="left"><code>Minutes</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>0-59</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>, - * /</code></td>
   * </tr>
   * <tr>
   * <td align="left"><code>Hours</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>0-23</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>, - * /</code></td>
   * </tr>
   * <tr>
   * <td align="left"><code>Day-of-month</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>1-31</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>, - * ? / L W</code></td>
   * </tr>
   * <tr>
   * <td align="left"><code>Month</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>0-11 or JAN-DEC</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>, - * /</code></td>
   * </tr>
   * <tr>
   * <td align="left"><code>Day-of-Week</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>1-7 or SUN-SAT</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>, - * ? / L #</code></td>
   * </tr>
   * <tr>
   * <td align="left"><code>Year (Optional)</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>empty, 1970-2199</code></td>
   * <td align="left">&nbsp;</th>
   * <td align="left"><code>, - * /</code></td>
   * </tr>
   * </table>
   * <P>
   * The '*' character is used to specify all values. For example, &quot;*&quot; in the
   * minute field means &quot;every minute&quot;.
   * <P>
   * The '?' character is allowed for the day-of-month and day-of-week fields. It is used to
   * specify 'no specific value'. This is useful when you need to specify something in one
   * of the two fields, but not the other.
   * <P>
   * The '-' character is used to specify ranges For example &quot;10-12&quot; in the hour
   * field means &quot;the hours 10, 11 and 12&quot;.
   * <P>
   * The ',' character is used to specify additional values. For example
   * &quot;MON,WED,FRI&quot; in the day-of-week field means &quot;the days Monday,
   * Wednesday, and Friday&quot;.
   * <P>
   * The '/' character is used to specify increments. For example &quot;0/15&quot; in the
   * seconds field means &quot;the seconds 0, 15, 30, and 45&quot;. And &quot;5/15&quot; in
   * the seconds field means &quot;the seconds 5, 20, 35, and 50&quot;. Specifying '*'
   * before the '/' is equivalent to specifying 0 is the value to start with. Essentially,
   * for each field in the expression, there is a set of numbers that can be turned on or
   * off. For seconds and minutes, the numbers range from 0 to 59. For hours 0 to 23, for
   * days of the month 0 to 31, and for months 0 to 11 (JAN to DEC). The &quot;/&quot;
   * character simply helps you turn on every &quot;nth&quot; value in the given set. Thus
   * &quot;7/6&quot; in the month field only turns on month &quot;7&quot;, it does NOT mean
   * every 6th month, please note that subtlety.
   * <P>
   * The 'L' character is allowed for the day-of-month and day-of-week fields. This
   * character is short-hand for &quot;last&quot;, but it has different meaning in each of
   * the two fields. For example, the value &quot;L&quot; in the day-of-month field means
   * &quot;the last day of the month&quot; - day 31 for January, day 28 for February on
   * non-leap years. If used in the day-of-week field by itself, it simply means
   * &quot;7&quot; or &quot;SAT&quot;. But if used in the day-of-week field after another
   * value, it means &quot;the last xxx day of the month&quot; - for example &quot;6L&quot;
   * means &quot;the last friday of the month&quot;. You can also specify an offset from the
   * last day of the month, such as "L-3" which would mean the third-to-last day of the
   * calendar month. <i>When using the 'L' option, it is important not to specify lists, or
   * ranges of values, as you'll get confusing/unexpected results.</i>
   * <P>
   * The 'W' character is allowed for the day-of-month field. This character is used to
   * specify the weekday (Monday-Friday) nearest the given day. As an example, if you were
   * to specify &quot;15W&quot; as the value for the day-of-month field, the meaning is:
   * &quot;the nearest weekday to the 15th of the month&quot;. So if the 15th is a Saturday,
   * the trigger will fire on Friday the 14th. If the 15th is a Sunday, the trigger will
   * fire on Monday the 16th. If the 15th is a Tuesday, then it will fire on Tuesday the
   * 15th. However if you specify &quot;1W&quot; as the value for day-of-month, and the 1st
   * is a Saturday, the trigger will fire on Monday the 3rd, as it will not 'jump' over the
   * boundary of a month's days. The 'W' character can only be specified when the
   * day-of-month is a single day, not a range or list of days.
   * <P>
   * The 'L' and 'W' characters can also be combined for the day-of-month expression to
   * yield 'LW', which translates to &quot;last weekday of the month&quot;.
   * <P>
   * The '#' character is allowed for the day-of-week field. This character is used to
   * specify &quot;the nth&quot; XXX day of the month. For example, the value of
   * &quot;6#3&quot; in the day-of-week field means the third Friday of the month (day 6 =
   * Friday and &quot;#3&quot; = the 3rd one in the month). Other examples: &quot;2#1&quot;
   * = the first Monday of the month and &quot;4#5&quot; = the fifth Wednesday of the month.
   * Note that if you specify &quot;#5&quot; and there is not 5 of the given day-of-week in
   * the month, then no firing will occur that month. If the '#' character is used, there
   * can only be one expression in the day-of-week field (&quot;3#1,6#3&quot; is not valid,
   * since there are two expressions).
   * <P>
   * <!--The 'C' character is allowed for the day-of-month and day-of-week fields. This
   * character is short-hand for "calendar". This means values are calculated against the
   * associated calendar, if any. If no calendar is associated, then it is equivalent to
   * having an all-inclusive calendar. A value of "5C" in the day-of-month field means "the
   * first day included by the calendar on or after the 5th". A value of "1C" in the
   * day-of-week field means "the first day included by the calendar on or after Sunday".-->
   * <P>
   * The legal characters and the names of months and days of the week are not case
   * sensitive.
   *
   * <p>
   * <b>NOTES:</b>
   * <ul>
   * <li>Support for specifying both a day-of-week and a day-of-month value is not complete
   * (you'll need to use the '?' character in one of these fields).</li>
   * <li>Overflowing ranges is supported - that is, having a larger number on the left hand
   * side than the right. You might do 22-2 to catch 10 o'clock at night until 2 o'clock in
   * the morning, or you might have NOV-FEB. It is very important to note that overuse of
   * overflowing ranges creates ranges that don't make sense and no effort has been made to
   * determine which interpretation CronExpression chooses. An example would be "0 0 14-6 ?
   * * FRI-MON".</li>
   * </ul>
   * </p>
   *
   * @author Sharada Jambula, James House
   * @author Contributions from Mads Henderson
   * @author Refactoring from CronTrigger to CronExpression by Aaron Craven
   *
   * Borrowed from quartz v2.3.1
   *
   */
  public final class CronExpression implements Serializable, Cloneable {
  
  	private static final long serialVersionUID = 12423409423L;
  
  	protected static final int SECOND = 0;
  
  	protected static final int MINUTE = 1;
  
  	protected static final int HOUR = 2;
  
  	protected static final int DAY_OF_MONTH = 3;
  
  	protected static final int MONTH = 4;
  
  	protected static final int DAY_OF_WEEK = 5;
  
  	protected static final int YEAR = 6;
  
  	protected static final int ALL_SPEC_INT = 99; // '*'
  
  	protected static final int NO_SPEC_INT = 98; // '?'
  
  	protected static final Integer ALL_SPEC = ALL_SPEC_INT;
  
  	protected static final Integer NO_SPEC = NO_SPEC_INT;
  
  	protected static final Map<String, Integer> monthMap = new HashMap<String, Integer>(20);
  
  	protected static final Map<String, Integer> dayMap = new HashMap<String, Integer>(60);
  	static {
  		monthMap.put("JAN", 0);
  		monthMap.put("FEB", 1);
  		monthMap.put("MAR", 2);
  		monthMap.put("APR", 3);
  		monthMap.put("MAY", 4);
  		monthMap.put("JUN", 5);
  		monthMap.put("JUL", 6);
  		monthMap.put("AUG", 7);
  		monthMap.put("SEP", 8);
  		monthMap.put("OCT", 9);
  		monthMap.put("NOV", 10);
  		monthMap.put("DEC", 11);
  
  		dayMap.put("SUN", 1);
  		dayMap.put("MON", 2);
  		dayMap.put("TUE", 3);
  		dayMap.put("WED", 4);
  		dayMap.put("THU", 5);
  		dayMap.put("FRI", 6);
  		dayMap.put("SAT", 7);
  	}
  
  	private final String cronExpression;
  
  	private TimeZone timeZone = null;
  
  	protected transient TreeSet<Integer> seconds;
  
  	protected transient TreeSet<Integer> minutes;
  
  	protected transient TreeSet<Integer> hours;
  
  	protected transient TreeSet<Integer> daysOfMonth;
  
  	protected transient TreeSet<Integer> months;
  
  	protected transient TreeSet<Integer> daysOfWeek;
  
  	protected transient TreeSet<Integer> years;
  
  	protected transient boolean lastdayOfWeek = false;
  
  	protected transient int nthdayOfWeek = 0;
  
  	protected transient boolean lastdayOfMonth = false;
  
  	protected transient boolean nearestWeekday = false;
  
  	protected transient int lastdayOffset = 0;
  
  	protected transient boolean expressionParsed = false;
  
  	public static final int MAX_YEAR = Calendar.getInstance().get(Calendar.YEAR) + 100;
  
  	/**
  	 * Constructs a new <CODE>CronExpression</CODE> based on the specified parameter.
  	 * @param cronExpression String representation of the cron expression the new object
  	 * should represent
  	 * @throws java.text.ParseException if the string expression cannot be parsed into a
  	 * valid <CODE>CronExpression</CODE>
  	 */
  	public CronExpression(String cronExpression) throws ParseException {
  		if (cronExpression == null) {
  			throw new IllegalArgumentException("cronExpression cannot be null");
  		}
  
  		this.cronExpression = cronExpression.toUpperCase(Locale.US);
  
  		buildExpression(this.cronExpression);
  	}
  
  	/**
  	 * Constructs a new {@code CronExpression} as a copy of an existing instance.
  	 * @param expression The existing cron expression to be copied
  	 */
  	public CronExpression(CronExpression expression) {
  		/*
  		 * We don't call the other constructor here since we need to swallow the
  		 * ParseException. We also elide some of the sanity checking as it is not
  		 * logically trippable.
  		 */
  		this.cronExpression = expression.getCronExpression();
  		try {
  			buildExpression(cronExpression);
  		}
  		catch (ParseException ex) {
  			throw new AssertionError();
  		}
  		if (expression.getTimeZone() != null) {
  			setTimeZone((TimeZone) expression.getTimeZone().clone());
  		}
  	}
  
  	/**
  	 * Indicates whether the given date satisfies the cron expression. Note that
  	 * milliseconds are ignored, so two Dates falling on different milliseconds of the
  	 * same second will always have the same result here.
  	 * @param date the date to evaluate
  	 * @return a boolean indicating whether the given date satisfies the cron expression
  	 */
  	public boolean isSatisfiedBy(Date date) {
  		Calendar testDateCal = Calendar.getInstance(getTimeZone());
  		testDateCal.setTime(date);
  		testDateCal.set(Calendar.MILLISECOND, 0);
  		Date originalDate = testDateCal.getTime();
  
  		testDateCal.add(Calendar.SECOND, -1);
  
  		Date timeAfter = getTimeAfter(testDateCal.getTime());
  
  		return ((timeAfter != null) && (timeAfter.equals(originalDate)));
  	}
  
  	/**
  	 * Returns the next date/time <I>after</I> the given date/time which satisfies the
  	 * cron expression.
  	 * @param date the date/time at which to begin the search for the next valid date/time
  	 * @return the next valid date/time
  	 */
  	public Date getNextValidTimeAfter(Date date) {
  		return getTimeAfter(date);
  	}
  
  	/**
  	 * Returns the next date/time <I>after</I> the given date/time which does <I>not</I>
  	 * satisfy the expression
  	 * @param date the date/time at which to begin the search for the next invalid
  	 * date/time
  	 * @return the next valid date/time
  	 */
  	public Date getNextInvalidTimeAfter(Date date) {
  		long difference = 1000;
  
  		// move back to the nearest second so differences will be accurate
  		Calendar adjustCal = Calendar.getInstance(getTimeZone());
  		adjustCal.setTime(date);
  		adjustCal.set(Calendar.MILLISECOND, 0);
  		Date lastDate = adjustCal.getTime();
  
  		Date newDate;
  
  		// FUTURE_TODO: (QUARTZ-481) IMPROVE THIS! The following is a BAD solution to this
  		// problem. Performance will be very bad here, depending on the cron expression.
  		// It is, however A solution.
  
  		// keep getting the next included time until it's farther than one second
  		// apart. At that point, lastDate is the last valid fire time. We return
  		// the second immediately following it.
  		while (difference == 1000) {
  			newDate = getTimeAfter(lastDate);
  			if (newDate == null) {
  				break;
  			}
  
  			difference = newDate.getTime() - lastDate.getTime();
  
  			if (difference == 1000) {
  				lastDate = newDate;
  			}
  		}
  
  		return new Date(lastDate.getTime() + 1000);
  	}
  
  	/**
  	 * Returns the time zone for which this <code>CronExpression</code> will be resolved.
  	 */
  	public TimeZone getTimeZone() {
  		if (timeZone == null) {
  			timeZone = TimeZone.getDefault();
  		}
  
  		return timeZone;
  	}
  
  	/**
  	 * Sets the time zone for which this <code>CronExpression</code> will be resolved.
  	 */
  	public void setTimeZone(TimeZone timeZone) {
  		this.timeZone = timeZone;
  	}
  
  	/**
  	 * Returns the string representation of the <CODE>CronExpression</CODE>
  	 * @return a string representation of the <CODE>CronExpression</CODE>
  	 */
  	@Override
  	public String toString() {
  		return cronExpression;
  	}
  
  	/**
  	 * Indicates whether the specified cron expression can be parsed into a valid cron
  	 * expression
  	 * @param cronExpression the expression to evaluate
  	 * @return a boolean indicating whether the given expression is a valid cron
  	 * expression
  	 */
  	public static boolean isValidExpression(String cronExpression) {
  
  		try {
  			new CronExpression(cronExpression);
  		}
  		catch (ParseException pe) {
  			return false;
  		}
  
  		return true;
  	}
  
  	public static void validateExpression(String cronExpression) throws ParseException {
  
  		new CronExpression(cronExpression);
  	}
  
  	////////////////////////////////////////////////////////////////////////////
  	//
  	// Expression Parsing Functions
  	//
  	////////////////////////////////////////////////////////////////////////////
  
  	protected void buildExpression(String expression) throws ParseException {
  		expressionParsed = true;
  
  		try {
  
  			if (seconds == null) {
  				seconds = new TreeSet<Integer>();
  			}
  			if (minutes == null) {
  				minutes = new TreeSet<Integer>();
  			}
  			if (hours == null) {
  				hours = new TreeSet<Integer>();
  			}
  			if (daysOfMonth == null) {
  				daysOfMonth = new TreeSet<Integer>();
  			}
  			if (months == null) {
  				months = new TreeSet<Integer>();
  			}
  			if (daysOfWeek == null) {
  				daysOfWeek = new TreeSet<Integer>();
  			}
  			if (years == null) {
  				years = new TreeSet<Integer>();
  			}
  
  			int exprOn = SECOND;
  
  			StringTokenizer exprsTok = new StringTokenizer(expression, " \t", false);
  
  			while (exprsTok.hasMoreTokens() && exprOn <= YEAR) {
  				String expr = exprsTok.nextToken().trim();
  
  				// throw an exception if L is used with other days of the month
  				if (exprOn == DAY_OF_MONTH && expr.indexOf('L') != -1 && expr.length() > 1 && expr.contains(",")) {
  					throw new ParseException(
  							"Support for specifying 'L' and 'LW' with other days of the month is not implemented", -1);
  				}
  				// throw an exception if L is used with other days of the week
  				if (exprOn == DAY_OF_WEEK && expr.indexOf('L') != -1 && expr.length() > 1 && expr.contains(",")) {
  					throw new ParseException(
  							"Support for specifying 'L' with other days of the week is not implemented", -1);
  				}
  				if (exprOn == DAY_OF_WEEK && expr.indexOf('#') != -1
  						&& expr.indexOf('#', expr.indexOf('#') + 1) != -1) {
  					throw new ParseException("Support for specifying multiple \"nth\" days is not implemented.", -1);
  				}
  
  				StringTokenizer vTok = new StringTokenizer(expr, ",");
  				while (vTok.hasMoreTokens()) {
  					String v = vTok.nextToken();
  					storeExpressionVals(0, v, exprOn);
  				}
  
  				exprOn++;
  			}
  
  			if (exprOn <= DAY_OF_WEEK) {
  				throw new ParseException("Unexpected end of expression.", expression.length());
  			}
  
  			if (exprOn <= YEAR) {
  				storeExpressionVals(0, "*", YEAR);
  			}
  
  			TreeSet<Integer> dow = getSet(DAY_OF_WEEK);
  			TreeSet<Integer> dom = getSet(DAY_OF_MONTH);
  
  			// Copying the logic from the UnsupportedOperationException below
  			boolean dayOfMSpec = !dom.contains(NO_SPEC);
  			boolean dayOfWSpec = !dow.contains(NO_SPEC);
  
  			if (!dayOfMSpec || dayOfWSpec) {
  				if (!dayOfWSpec || dayOfMSpec) {
  					throw new ParseException(
  							"Support for specifying both a day-of-week AND a day-of-month parameter is not implemented.",
  							0);
  				}
  			}
  		}
  		catch (ParseException pe) {
  			throw pe;
  		}
  		catch (Exception e) {
  			throw new ParseException("Illegal cron expression format (" + e.toString() + ")", 0);
  		}
  	}
  
  	protected int storeExpressionVals(int pos, String s, int type) throws ParseException {
  
  		int incr = 0;
  		int i = skipWhiteSpace(pos, s);
  		if (i >= s.length()) {
  			return i;
  		}
  		char c = s.charAt(i);
  		if ((c >= 'A') && (c <= 'Z') && (!s.equals("L")) && (!s.equals("LW")) && (!s.matches("^L-[0-9]*[W]?"))) {
  			String sub = s.substring(i, i + 3);
  			int sval = -1;
  			int eval = -1;
  			if (type == MONTH) {
  				sval = getMonthNumber(sub) + 1;
  				if (sval <= 0) {
  					throw new ParseException("Invalid Month value: '" + sub + "'", i);
  				}
  				if (s.length() > i + 3) {
  					c = s.charAt(i + 3);
  					if (c == '-') {
  						i += 4;
  						sub = s.substring(i, i + 3);
  						eval = getMonthNumber(sub) + 1;
  						if (eval <= 0) {
  							throw new ParseException("Invalid Month value: '" + sub + "'", i);
  						}
  					}
  				}
  			}
  			else if (type == DAY_OF_WEEK) {
  				sval = getDayOfWeekNumber(sub);
  				if (sval < 0) {
  					throw new ParseException("Invalid Day-of-Week value: '" + sub + "'", i);
  				}
  				if (s.length() > i + 3) {
  					c = s.charAt(i + 3);
  					if (c == '-') {
  						i += 4;
  						sub = s.substring(i, i + 3);
  						eval = getDayOfWeekNumber(sub);
  						if (eval < 0) {
  							throw new ParseException("Invalid Day-of-Week value: '" + sub + "'", i);
  						}
  					}
  					else if (c == '#') {
  						try {
  							i += 4;
  							nthdayOfWeek = Integer.parseInt(s.substring(i));
  							if (nthdayOfWeek < 1 || nthdayOfWeek > 5) {
  								throw new Exception();
  							}
  						}
  						catch (Exception e) {
  							throw new ParseException("A numeric value between 1 and 5 must follow the '#' option", i);
  						}
  					}
  					else if (c == 'L') {
  						lastdayOfWeek = true;
  						i++;
  					}
  				}
  
  			}
  			else {
  				throw new ParseException("Illegal characters for this position: '" + sub + "'", i);
  			}
  			if (eval != -1) {
  				incr = 1;
  			}
  			addToSet(sval, eval, incr, type);
  			return (i + 3);
  		}
  
  		if (c == '?') {
  			i++;
  			if ((i + 1) < s.length() && (s.charAt(i) != ' ' && s.charAt(i + 1) != '\t')) {
  				throw new ParseException("Illegal character after '?': " + s.charAt(i), i);
  			}
  			if (type != DAY_OF_WEEK && type != DAY_OF_MONTH) {
  				throw new ParseException("'?' can only be specified for Day-of-Month or Day-of-Week.", i);
  			}
  			if (type == DAY_OF_WEEK && !lastdayOfMonth) {
  				int val = daysOfMonth.last();
  				if (val == NO_SPEC_INT) {
  					throw new ParseException("'?' can only be specified for Day-of-Month -OR- Day-of-Week.", i);
  				}
  			}
  
  			addToSet(NO_SPEC_INT, -1, 0, type);
  			return i;
  		}
  
  		if (c == '*' || c == '/') {
  			if (c == '*' && (i + 1) >= s.length()) {
  				addToSet(ALL_SPEC_INT, -1, incr, type);
  				return i + 1;
  			}
  			else if (c == '/' && ((i + 1) >= s.length() || s.charAt(i + 1) == ' ' || s.charAt(i + 1) == '\t')) {
  				throw new ParseException("'/' must be followed by an integer.", i);
  			}
  			else if (c == '*') {
  				i++;
  			}
  			c = s.charAt(i);
  			if (c == '/') { // is an increment specified?
  				i++;
  				if (i >= s.length()) {
  					throw new ParseException("Unexpected end of string.", i);
  				}
  
  				incr = getNumericValue(s, i);
  
  				i++;
  				if (incr > 10) {
  					i++;
  				}
  				checkIncrementRange(incr, type, i);
  			}
  			else {
  				incr = 1;
  			}
  
  			addToSet(ALL_SPEC_INT, -1, incr, type);
  			return i;
  		}
  		else if (c == 'L') {
  			i++;
  			if (type == DAY_OF_MONTH) {
  				lastdayOfMonth = true;
  			}
  			if (type == DAY_OF_WEEK) {
  				addToSet(7, 7, 0, type);
  			}
  			if (type == DAY_OF_MONTH && s.length() > i) {
  				c = s.charAt(i);
  				if (c == '-') {
  					ValueSet vs = getValue(0, s, i + 1);
  					lastdayOffset = vs.value;
  					if (lastdayOffset > 30) {
  						throw new ParseException("Offset from last day must be <= 30", i + 1);
  					}
  					i = vs.pos;
  				}
  				if (s.length() > i) {
  					c = s.charAt(i);
  					if (c == 'W') {
  						nearestWeekday = true;
  						i++;
  					}
  				}
  			}
  			return i;
  		}
  		else if (c >= '0' && c <= '9') {
  			int val = Integer.parseInt(String.valueOf(c));
  			i++;
  			if (i >= s.length()) {
  				addToSet(val, -1, -1, type);
  			}
  			else {
  				c = s.charAt(i);
  				if (c >= '0' && c <= '9') {
  					ValueSet vs = getValue(val, s, i);
  					val = vs.value;
  					i = vs.pos;
  				}
  				i = checkNext(i, s, val, type);
  				return i;
  			}
  		}
  		else {
  			throw new ParseException("Unexpected character: " + c, i);
  		}
  
  		return i;
  	}
  
  	private void checkIncrementRange(int incr, int type, int idxPos) throws ParseException {
  		if (incr > 59 && (type == SECOND || type == MINUTE)) {
  			throw new ParseException("Increment > 60 : " + incr, idxPos);
  		}
  		else if (incr > 23 && (type == HOUR)) {
  			throw new ParseException("Increment > 24 : " + incr, idxPos);
  		}
  		else if (incr > 31 && (type == DAY_OF_MONTH)) {
  			throw new ParseException("Increment > 31 : " + incr, idxPos);
  		}
  		else if (incr > 7 && (type == DAY_OF_WEEK)) {
  			throw new ParseException("Increment > 7 : " + incr, idxPos);
  		}
  		else if (incr > 12 && (type == MONTH)) {
  			throw new ParseException("Increment > 12 : " + incr, idxPos);
  		}
  	}
  
  	protected int checkNext(int pos, String s, int val, int type) throws ParseException {
  
  		int end = -1;
  		int i = pos;
  
  		if (i >= s.length()) {
  			addToSet(val, end, -1, type);
  			return i;
  		}
  
  		char c = s.charAt(pos);
  
  		if (c == 'L') {
  			if (type == DAY_OF_WEEK) {
  				if (val < 1 || val > 7) {
  					throw new ParseException("Day-of-Week values must be between 1 and 7", -1);
  				}
  				lastdayOfWeek = true;
  			}
  			else {
  				throw new ParseException("'L' option is not valid here. (pos=" + i + ")", i);
  			}
  			TreeSet<Integer> set = getSet(type);
  			set.add(val);
  			i++;
  			return i;
  		}
  
  		if (c == 'W') {
  			if (type == DAY_OF_MONTH) {
  				nearestWeekday = true;
  			}
  			else {
  				throw new ParseException("'W' option is not valid here. (pos=" + i + ")", i);
  			}
  			if (val > 31) {
  				throw new ParseException(
  						"The 'W' option does not make sense with values larger than 31 (max number of days in a month)",
  						i);
  			}
  			TreeSet<Integer> set = getSet(type);
  			set.add(val);
  			i++;
  			return i;
  		}
  
  		if (c == '#') {
  			if (type != DAY_OF_WEEK) {
  				throw new ParseException("'#' option is not valid here. (pos=" + i + ")", i);
  			}
  			i++;
  			try {
  				nthdayOfWeek = Integer.parseInt(s.substring(i));
  				if (nthdayOfWeek < 1 || nthdayOfWeek > 5) {
  					throw new Exception();
  				}
  			}
  			catch (Exception e) {
  				throw new ParseException("A numeric value between 1 and 5 must follow the '#' option", i);
  			}
  
  			TreeSet<Integer> set = getSet(type);
  			set.add(val);
  			i++;
  			return i;
  		}
  
  		if (c == '-') {
  			i++;
  			c = s.charAt(i);
  			int v = Integer.parseInt(String.valueOf(c));
  			end = v;
  			i++;
  			if (i >= s.length()) {
  				addToSet(val, end, 1, type);
  				return i;
  			}
  			c = s.charAt(i);
  			if (c >= '0' && c <= '9') {
  				ValueSet vs = getValue(v, s, i);
  				end = vs.value;
  				i = vs.pos;
  			}
  			if (i < s.length() && ((c = s.charAt(i)) == '/')) {
  				i++;
  				c = s.charAt(i);
  				int v2 = Integer.parseInt(String.valueOf(c));
  				i++;
  				if (i >= s.length()) {
  					addToSet(val, end, v2, type);
  					return i;
  				}
  				c = s.charAt(i);
  				if (c >= '0' && c <= '9') {
  					ValueSet vs = getValue(v2, s, i);
  					int v3 = vs.value;
  					addToSet(val, end, v3, type);
  					i = vs.pos;
  					return i;
  				}
  				else {
  					addToSet(val, end, v2, type);
  					return i;
  				}
  			}
  			else {
  				addToSet(val, end, 1, type);
  				return i;
  			}
  		}
  
  		if (c == '/') {
  			if ((i + 1) >= s.length() || s.charAt(i + 1) == ' ' || s.charAt(i + 1) == '\t') {
  				throw new ParseException("'/' must be followed by an integer.", i);
  			}
  
  			i++;
  			c = s.charAt(i);
  			int v2 = Integer.parseInt(String.valueOf(c));
  			i++;
  			if (i >= s.length()) {
  				checkIncrementRange(v2, type, i);
  				addToSet(val, end, v2, type);
  				return i;
  			}
  			c = s.charAt(i);
  			if (c >= '0' && c <= '9') {
  				ValueSet vs = getValue(v2, s, i);
  				int v3 = vs.value;
  				checkIncrementRange(v3, type, i);
  				addToSet(val, end, v3, type);
  				i = vs.pos;
  				return i;
  			}
  			else {
  				throw new ParseException("Unexpected character '" + c + "' after '/'", i);
  			}
  		}
  
  		addToSet(val, end, 0, type);
  		i++;
  		return i;
  	}
  
  	public String getCronExpression() {
  		return cronExpression;
  	}
  
  	public String getExpressionSummary() {
  		StringBuilder buf = new StringBuilder();
  
  		buf.append("seconds: ");
  		buf.append(getExpressionSetSummary(seconds));
  		buf.append("\n");
  		buf.append("minutes: ");
  		buf.append(getExpressionSetSummary(minutes));
  		buf.append("\n");
  		buf.append("hours: ");
  		buf.append(getExpressionSetSummary(hours));
  		buf.append("\n");
  		buf.append("daysOfMonth: ");
  		buf.append(getExpressionSetSummary(daysOfMonth));
  		buf.append("\n");
  		buf.append("months: ");
  		buf.append(getExpressionSetSummary(months));
  		buf.append("\n");
  		buf.append("daysOfWeek: ");
  		buf.append(getExpressionSetSummary(daysOfWeek));
  		buf.append("\n");
  		buf.append("lastdayOfWeek: ");
  		buf.append(lastdayOfWeek);
  		buf.append("\n");
  		buf.append("nearestWeekday: ");
  		buf.append(nearestWeekday);
  		buf.append("\n");
  		buf.append("NthDayOfWeek: ");
  		buf.append(nthdayOfWeek);
  		buf.append("\n");
  		buf.append("lastdayOfMonth: ");
  		buf.append(lastdayOfMonth);
  		buf.append("\n");
  		buf.append("years: ");
  		buf.append(getExpressionSetSummary(years));
  		buf.append("\n");
  
  		return buf.toString();
  	}
  
  	protected String getExpressionSetSummary(java.util.Set<Integer> set) {
  
  		if (set.contains(NO_SPEC)) {
  			return "?";
  		}
  		if (set.contains(ALL_SPEC)) {
  			return "*";
  		}
  
  		StringBuilder buf = new StringBuilder();
  
  		Iterator<Integer> itr = set.iterator();
  		boolean first = true;
  		while (itr.hasNext()) {
  			Integer iVal = itr.next();
  			String val = iVal.toString();
  			if (!first) {
  				buf.append(",");
  			}
  			buf.append(val);
  			first = false;
  		}
  
  		return buf.toString();
  	}
  
  	protected String getExpressionSetSummary(java.util.ArrayList<Integer> list) {
  
  		if (list.contains(NO_SPEC)) {
  			return "?";
  		}
  		if (list.contains(ALL_SPEC)) {
  			return "*";
  		}
  
  		StringBuilder buf = new StringBuilder();
  
  		Iterator<Integer> itr = list.iterator();
  		boolean first = true;
  		while (itr.hasNext()) {
  			Integer iVal = itr.next();
  			String val = iVal.toString();
  			if (!first) {
  				buf.append(",");
  			}
  			buf.append(val);
  			first = false;
  		}
  
  		return buf.toString();
  	}
  
  	protected int skipWhiteSpace(int i, String s) {
  		for (; i < s.length() && (s.charAt(i) == ' ' || s.charAt(i) == '\t'); i++) {
  		}
  
  		return i;
  	}
  
  	protected int findNextWhiteSpace(int i, String s) {
  		for (; i < s.length() && (s.charAt(i) != ' ' || s.charAt(i) != '\t'); i++) {
  		}
  
  		return i;
  	}
  
  	protected void addToSet(int val, int end, int incr, int type) throws ParseException {
  
  		TreeSet<Integer> set = getSet(type);
  
  		if (type == SECOND || type == MINUTE) {
  			if ((val < 0 || val > 59 || end > 59) && (val != ALL_SPEC_INT)) {
  				throw new ParseException("Minute and Second values must be between 0 and 59", -1);
  			}
  		}
  		else if (type == HOUR) {
  			if ((val < 0 || val > 23 || end > 23) && (val != ALL_SPEC_INT)) {
  				throw new ParseException("Hour values must be between 0 and 23", -1);
  			}
  		}
  		else if (type == DAY_OF_MONTH) {
  			if ((val < 1 || val > 31 || end > 31) && (val != ALL_SPEC_INT) && (val != NO_SPEC_INT)) {
  				throw new ParseException("Day of month values must be between 1 and 31", -1);
  			}
  		}
  		else if (type == MONTH) {
  			if ((val < 1 || val > 12 || end > 12) && (val != ALL_SPEC_INT)) {
  				throw new ParseException("Month values must be between 1 and 12", -1);
  			}
  		}
  		else if (type == DAY_OF_WEEK) {
  			if ((val == 0 || val > 7 || end > 7) && (val != ALL_SPEC_INT) && (val != NO_SPEC_INT)) {
  				throw new ParseException("Day-of-Week values must be between 1 and 7", -1);
  			}
  		}
  
  		if ((incr == 0 || incr == -1) && val != ALL_SPEC_INT) {
  			if (val != -1) {
  				set.add(val);
  			}
  			else {
  				set.add(NO_SPEC);
  			}
  
  			return;
  		}
  
  		int startAt = val;
  		int stopAt = end;
  
  		if (val == ALL_SPEC_INT && incr <= 0) {
  			incr = 1;
  			set.add(ALL_SPEC); // put in a marker, but also fill values
  		}
  
  		if (type == SECOND || type == MINUTE) {
  			if (stopAt == -1) {
  				stopAt = 59;
  			}
  			if (startAt == -1 || startAt == ALL_SPEC_INT) {
  				startAt = 0;
  			}
  		}
  		else if (type == HOUR) {
  			if (stopAt == -1) {
  				stopAt = 23;
  			}
  			if (startAt == -1 || startAt == ALL_SPEC_INT) {
  				startAt = 0;
  			}
  		}
  		else if (type == DAY_OF_MONTH) {
  			if (stopAt == -1) {
  				stopAt = 31;
  			}
  			if (startAt == -1 || startAt == ALL_SPEC_INT) {
  				startAt = 1;
  			}
  		}
  		else if (type == MONTH) {
  			if (stopAt == -1) {
  				stopAt = 12;
  			}
  			if (startAt == -1 || startAt == ALL_SPEC_INT) {
  				startAt = 1;
  			}
  		}
  		else if (type == DAY_OF_WEEK) {
  			if (stopAt == -1) {
  				stopAt = 7;
  			}
  			if (startAt == -1 || startAt == ALL_SPEC_INT) {
  				startAt = 1;
  			}
  		}
  		else if (type == YEAR) {
  			if (stopAt == -1) {
  				stopAt = MAX_YEAR;
  			}
  			if (startAt == -1 || startAt == ALL_SPEC_INT) {
  				startAt = 1970;
  			}
  		}
  
  		// if the end of the range is before the start, then we need to overflow into
  		// the next day, month etc. This is done by adding the maximum amount for that
  		// type, and using modulus max to determine the value being added.
  		int max = -1;
  		if (stopAt < startAt) {
  			switch (type) {
  			case SECOND:
  				max = 60;
  				break;
  			case MINUTE:
  				max = 60;
  				break;
  			case HOUR:
  				max = 24;
  				break;
  			case MONTH:
  				max = 12;
  				break;
  			case DAY_OF_WEEK:
  				max = 7;
  				break;
  			case DAY_OF_MONTH:
  				max = 31;
  				break;
  			case YEAR:
  				throw new IllegalArgumentException("Start year must be less than stop year");
  			default:
  				throw new IllegalArgumentException("Unexpected type encountered");
  			}
  			stopAt += max;
  		}
  
  		for (int i = startAt; i <= stopAt; i += incr) {
  			if (max == -1) {
  				// ie: there's no max to overflow over
  				set.add(i);
  			}
  			else {
  				// take the modulus to get the real value
  				int i2 = i % max;
  
  				// 1-indexed ranges should not include 0, and should include their max
  				if (i2 == 0 && (type == MONTH || type == DAY_OF_WEEK || type == DAY_OF_MONTH)) {
  					i2 = max;
  				}
  
  				set.add(i2);
  			}
  		}
  	}
  
  	TreeSet<Integer> getSet(int type) {
  		switch (type) {
  		case SECOND:
  			return seconds;
  		case MINUTE:
  			return minutes;
  		case HOUR:
  			return hours;
  		case DAY_OF_MONTH:
  			return daysOfMonth;
  		case MONTH:
  			return months;
  		case DAY_OF_WEEK:
  			return daysOfWeek;
  		case YEAR:
  			return years;
  		default:
  			return null;
  		}
  	}
  
  	protected ValueSet getValue(int v, String s, int i) {
  		char c = s.charAt(i);
  		StringBuilder s1 = new StringBuilder(String.valueOf(v));
  		while (c >= '0' && c <= '9') {
  			s1.append(c);
  			i++;
  			if (i >= s.length()) {
  				break;
  			}
  			c = s.charAt(i);
  		}
  		ValueSet val = new ValueSet();
  
  		val.pos = (i < s.length()) ? i : i + 1;
  		val.value = Integer.parseInt(s1.toString());
  		return val;
  	}
  
  	protected int getNumericValue(String s, int i) {
  		int endOfVal = findNextWhiteSpace(i, s);
  		String val = s.substring(i, endOfVal);
  		return Integer.parseInt(val);
  	}
  
  	protected int getMonthNumber(String s) {
  		Integer integer = monthMap.get(s);
  
  		if (integer == null) {
  			return -1;
  		}
  
  		return integer;
  	}
  
  	protected int getDayOfWeekNumber(String s) {
  		Integer integer = dayMap.get(s);
  
  		if (integer == null) {
  			return -1;
  		}
  
  		return integer;
  	}
  
  	////////////////////////////////////////////////////////////////////////////
  	//
  	// Computation Functions
  	//
  	////////////////////////////////////////////////////////////////////////////
  
  	public Date getTimeAfter(Date afterTime) {
  
  		// Computation is based on Gregorian year only.
  		Calendar cl = new java.util.GregorianCalendar(getTimeZone());
  
  		// move ahead one second, since we're computing the time *after* the
  		// given time
  		afterTime = new Date(afterTime.getTime() + 1000);
  		// CronTrigger does not deal with milliseconds
  		cl.setTime(afterTime);
  		cl.set(Calendar.MILLISECOND, 0);
  
  		boolean gotOne = false;
  		// loop until we've computed the next time, or we've past the endTime
  		while (!gotOne) {
  
  			// if (endTime != null && cl.getTime().after(endTime)) return null;
  			if (cl.get(Calendar.YEAR) > 2999) { // prevent endless loop...
  				return null;
  			}
  
  			SortedSet<Integer> st = null;
  			int t = 0;
  
  			int sec = cl.get(Calendar.SECOND);
  			int min = cl.get(Calendar.MINUTE);
  
  			// get second.................................................
  			st = seconds.tailSet(sec);
  			if (st != null && st.size() != 0) {
  				sec = st.first();
  			}
  			else {
  				sec = seconds.first();
  				min++;
  				cl.set(Calendar.MINUTE, min);
  			}
  			cl.set(Calendar.SECOND, sec);
  
  			min = cl.get(Calendar.MINUTE);
  			int hr = cl.get(Calendar.HOUR_OF_DAY);
  			t = -1;
  
  			// get minute.................................................
  			st = minutes.tailSet(min);
  			if (st != null && st.size() != 0) {
  				t = min;
  				min = st.first();
  			}
  			else {
  				min = minutes.first();
  				hr++;
  			}
  			if (min != t) {
  				cl.set(Calendar.SECOND, 0);
  				cl.set(Calendar.MINUTE, min);
  				setCalendarHour(cl, hr);
  				continue;
  			}
  			cl.set(Calendar.MINUTE, min);
  
  			hr = cl.get(Calendar.HOUR_OF_DAY);
  			int day = cl.get(Calendar.DAY_OF_MONTH);
  			t = -1;
  
  			// get hour...................................................
  			st = hours.tailSet(hr);
  			if (st != null && st.size() != 0) {
  				t = hr;
  				hr = st.first();
  			}
  			else {
  				hr = hours.first();
  				day++;
  			}
  			if (hr != t) {
  				cl.set(Calendar.SECOND, 0);
  				cl.set(Calendar.MINUTE, 0);
  				cl.set(Calendar.DAY_OF_MONTH, day);
  				setCalendarHour(cl, hr);
  				continue;
  			}
  			cl.set(Calendar.HOUR_OF_DAY, hr);
  
  			day = cl.get(Calendar.DAY_OF_MONTH);
  			int mon = cl.get(Calendar.MONTH) + 1;
  			// '+ 1' because calendar is 0-based for this field, and we are
  			// 1-based
  			t = -1;
  			int tmon = mon;
  
  			// get day...................................................
  			boolean dayOfMSpec = !daysOfMonth.contains(NO_SPEC);
  			boolean dayOfWSpec = !daysOfWeek.contains(NO_SPEC);
  			if (dayOfMSpec && !dayOfWSpec) { // get day by day of month rule
  				st = daysOfMonth.tailSet(day);
  				if (lastdayOfMonth) {
  					if (!nearestWeekday) {
  						t = day;
  						day = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
  						day -= lastdayOffset;
  						if (t > day) {
  							mon++;
  							if (mon > 12) {
  								mon = 1;
  								tmon = 3333; // ensure test of mon != tmon further below
  												// fails
  								cl.add(Calendar.YEAR, 1);
  							}
  							day = 1;
  						}
  					}
  					else {
  						t = day;
  						day = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
  						day -= lastdayOffset;
  
  						java.util.Calendar tcal = java.util.Calendar.getInstance(getTimeZone());
  						tcal.set(Calendar.SECOND, 0);
  						tcal.set(Calendar.MINUTE, 0);
  						tcal.set(Calendar.HOUR_OF_DAY, 0);
  						tcal.set(Calendar.DAY_OF_MONTH, day);
  						tcal.set(Calendar.MONTH, mon - 1);
  						tcal.set(Calendar.YEAR, cl.get(Calendar.YEAR));
  
  						int ldom = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
  						int dow = tcal.get(Calendar.DAY_OF_WEEK);
  
  						if (dow == Calendar.SATURDAY && day == 1) {
  							day += 2;
  						}
  						else if (dow == Calendar.SATURDAY) {
  							day -= 1;
  						}
  						else if (dow == Calendar.SUNDAY && day == ldom) {
  							day -= 2;
  						}
  						else if (dow == Calendar.SUNDAY) {
  							day += 1;
  						}
  
  						tcal.set(Calendar.SECOND, sec);
  						tcal.set(Calendar.MINUTE, min);
  						tcal.set(Calendar.HOUR_OF_DAY, hr);
  						tcal.set(Calendar.DAY_OF_MONTH, day);
  						tcal.set(Calendar.MONTH, mon - 1);
  						Date nTime = tcal.getTime();
  						if (nTime.before(afterTime)) {
  							day = 1;
  							mon++;
  						}
  					}
  				}
  				else if (nearestWeekday) {
  					t = day;
  					day = daysOfMonth.first();
  
  					java.util.Calendar tcal = java.util.Calendar.getInstance(getTimeZone());
  					tcal.set(Calendar.SECOND, 0);
  					tcal.set(Calendar.MINUTE, 0);
  					tcal.set(Calendar.HOUR_OF_DAY, 0);
  					tcal.set(Calendar.DAY_OF_MONTH, day);
  					tcal.set(Calendar.MONTH, mon - 1);
  					tcal.set(Calendar.YEAR, cl.get(Calendar.YEAR));
  
  					int ldom = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
  					int dow = tcal.get(Calendar.DAY_OF_WEEK);
  
  					if (dow == Calendar.SATURDAY && day == 1) {
  						day += 2;
  					}
  					else if (dow == Calendar.SATURDAY) {
  						day -= 1;
  					}
  					else if (dow == Calendar.SUNDAY && day == ldom) {
  						day -= 2;
  					}
  					else if (dow == Calendar.SUNDAY) {
  						day += 1;
  					}
  
  					tcal.set(Calendar.SECOND, sec);
  					tcal.set(Calendar.MINUTE, min);
  					tcal.set(Calendar.HOUR_OF_DAY, hr);
  					tcal.set(Calendar.DAY_OF_MONTH, day);
  					tcal.set(Calendar.MONTH, mon - 1);
  					Date nTime = tcal.getTime();
  					if (nTime.before(afterTime)) {
  						day = daysOfMonth.first();
  						mon++;
  					}
  				}
  				else if (st != null && st.size() != 0) {
  					t = day;
  					day = st.first();
  					// make sure we don't over-run a short month, such as february
  					int lastDay = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
  					if (day > lastDay) {
  						day = daysOfMonth.first();
  						mon++;
  					}
  				}
  				else {
  					day = daysOfMonth.first();
  					mon++;
  				}
  
  				if (day != t || mon != tmon) {
  					cl.set(Calendar.SECOND, 0);
  					cl.set(Calendar.MINUTE, 0);
  					cl.set(Calendar.HOUR_OF_DAY, 0);
  					cl.set(Calendar.DAY_OF_MONTH, day);
  					cl.set(Calendar.MONTH, mon - 1);
  					// '- 1' because calendar is 0-based for this field, and we
  					// are 1-based
  					continue;
  				}
  			}
  			else if (dayOfWSpec && !dayOfMSpec) { // get day by day of week rule
  				if (lastdayOfWeek) { // are we looking for the last XXX day of
  					// the month?
  					int dow = daysOfWeek.first(); // desired
  					// d-o-w
  					int cDow = cl.get(Calendar.DAY_OF_WEEK); // current d-o-w
  					int daysToAdd = 0;
  					if (cDow < dow) {
  						daysToAdd = dow - cDow;
  					}
  					if (cDow > dow) {
  						daysToAdd = dow + (7 - cDow);
  					}
  
  					int lDay = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
  
  					if (day + daysToAdd > lDay) { // did we already miss the
  						// last one?
  						cl.set(Calendar.SECOND, 0);
  						cl.set(Calendar.MINUTE, 0);
  						cl.set(Calendar.HOUR_OF_DAY, 0);
  						cl.set(Calendar.DAY_OF_MONTH, 1);
  						cl.set(Calendar.MONTH, mon);
  						// no '- 1' here because we are promoting the month
  						continue;
  					}
  
  					// find date of last occurrence of this day in this month...
  					while ((day + daysToAdd + 7) <= lDay) {
  						daysToAdd += 7;
  					}
  
  					day += daysToAdd;
  
  					if (daysToAdd > 0) {
  						cl.set(Calendar.SECOND, 0);
  						cl.set(Calendar.MINUTE, 0);
  						cl.set(Calendar.HOUR_OF_DAY, 0);
  						cl.set(Calendar.DAY_OF_MONTH, day);
  						cl.set(Calendar.MONTH, mon - 1);
  						// '- 1' here because we are not promoting the month
  						continue;
  					}
  
  				}
  				else if (nthdayOfWeek != 0) {
  					// are we looking for the Nth XXX day in the month?
  					int dow = daysOfWeek.first(); // desired
  					// d-o-w
  					int cDow = cl.get(Calendar.DAY_OF_WEEK); // current d-o-w
  					int daysToAdd = 0;
  					if (cDow < dow) {
  						daysToAdd = dow - cDow;
  					}
  					else if (cDow > dow) {
  						daysToAdd = dow + (7 - cDow);
  					}
  
  					boolean dayShifted = false;
  					if (daysToAdd > 0) {
  						dayShifted = true;
  					}
  
  					day += daysToAdd;
  					int weekOfMonth = day / 7;
  					if (day % 7 > 0) {
  						weekOfMonth++;
  					}
  
  					daysToAdd = (nthdayOfWeek - weekOfMonth) * 7;
  					day += daysToAdd;
  					if (daysToAdd < 0 || day > getLastDayOfMonth(mon, cl.get(Calendar.YEAR))) {
  						cl.set(Calendar.SECOND, 0);
  						cl.set(Calendar.MINUTE, 0);
  						cl.set(Calendar.HOUR_OF_DAY, 0);
  						cl.set(Calendar.DAY_OF_MONTH, 1);
  						cl.set(Calendar.MONTH, mon);
  						// no '- 1' here because we are promoting the month
  						continue;
  					}
  					else if (daysToAdd > 0 || dayShifted) {
  						cl.set(Calendar.SECOND, 0);
  						cl.set(Calendar.MINUTE, 0);
  						cl.set(Calendar.HOUR_OF_DAY, 0);
  						cl.set(Calendar.DAY_OF_MONTH, day);
  						cl.set(Calendar.MONTH, mon - 1);
  						// '- 1' here because we are NOT promoting the month
  						continue;
  					}
  				}
  				else {
  					int cDow = cl.get(Calendar.DAY_OF_WEEK); // current d-o-w
  					int dow = daysOfWeek.first(); // desired
  					// d-o-w
  					st = daysOfWeek.tailSet(cDow);
  					if (st != null && st.size() > 0) {
  						dow = st.first();
  					}
  
  					int daysToAdd = 0;
  					if (cDow < dow) {
  						daysToAdd = dow - cDow;
  					}
  					if (cDow > dow) {
  						daysToAdd = dow + (7 - cDow);
  					}
  
  					int lDay = getLastDayOfMonth(mon, cl.get(Calendar.YEAR));
  
  					if (day + daysToAdd > lDay) { // will we pass the end of
  						// the month?
  						cl.set(Calendar.SECOND, 0);
  						cl.set(Calendar.MINUTE, 0);
  						cl.set(Calendar.HOUR_OF_DAY, 0);
  						cl.set(Calendar.DAY_OF_MONTH, 1);
  						cl.set(Calendar.MONTH, mon);
  						// no '- 1' here because we are promoting the month
  						continue;
  					}
  					else if (daysToAdd > 0) { // are we swithing days?
  						cl.set(Calendar.SECOND, 0);
  						cl.set(Calendar.MINUTE, 0);
  						cl.set(Calendar.HOUR_OF_DAY, 0);
  						cl.set(Calendar.DAY_OF_MONTH, day + daysToAdd);
  						cl.set(Calendar.MONTH, mon - 1);
  						// '- 1' because calendar is 0-based for this field,
  						// and we are 1-based
  						continue;
  					}
  				}
  			}
  			else { // dayOfWSpec && !dayOfMSpec
  				throw new UnsupportedOperationException(
  						"Support for specifying both a day-of-week AND a day-of-month parameter is not implemented.");
  			}
  			cl.set(Calendar.DAY_OF_MONTH, day);
  
  			mon = cl.get(Calendar.MONTH) + 1;
  			// '+ 1' because calendar is 0-based for this field, and we are
  			// 1-based
  			int year = cl.get(Calendar.YEAR);
  			t = -1;
  
  			// test for expressions that never generate a valid fire date,
  			// but keep looping...
  			if (year > MAX_YEAR) {
  				return null;
  			}
  
  			// get month...................................................
  			st = months.tailSet(mon);
  			if (st != null && st.size() != 0) {
  				t = mon;
  				mon = st.first();
  			}
  			else {
  				mon = months.first();
  				year++;
  			}
  			if (mon != t) {
  				cl.set(Calendar.SECOND, 0);
  				cl.set(Calendar.MINUTE, 0);
  				cl.set(Calendar.HOUR_OF_DAY, 0);
  				cl.set(Calendar.DAY_OF_MONTH, 1);
  				cl.set(Calendar.MONTH, mon - 1);
  				// '- 1' because calendar is 0-based for this field, and we are
  				// 1-based
  				cl.set(Calendar.YEAR, year);
  				continue;
  			}
  			cl.set(Calendar.MONTH, mon - 1);
  			// '- 1' because calendar is 0-based for this field, and we are
  			// 1-based
  
  			year = cl.get(Calendar.YEAR);
  			t = -1;
  
  			// get year...................................................
  			st = years.tailSet(year);
  			if (st != null && st.size() != 0) {
  				t = year;
  				year = st.first();
  			}
  			else {
  				return null; // ran out of years...
  			}
  
  			if (year != t) {
  				cl.set(Calendar.SECOND, 0);
  				cl.set(Calendar.MINUTE, 0);
  				cl.set(Calendar.HOUR_OF_DAY, 0);
  				cl.set(Calendar.DAY_OF_MONTH, 1);
  				cl.set(Calendar.MONTH, 0);
  				// '- 1' because calendar is 0-based for this field, and we are
  				// 1-based
  				cl.set(Calendar.YEAR, year);
  				continue;
  			}
  			cl.set(Calendar.YEAR, year);
  
  			gotOne = true;
  		} // while( !done )
  
  		return cl.getTime();
  	}
  
  	/**
  	 * Advance the calendar to the particular hour paying particular attention to daylight
  	 * saving problems.
  	 * @param cal the calendar to operate on
  	 * @param hour the hour to set
  	 */
  	protected void setCalendarHour(Calendar cal, int hour) {
  		cal.set(java.util.Calendar.HOUR_OF_DAY, hour);
  		if (cal.get(java.util.Calendar.HOUR_OF_DAY) != hour && hour != 24) {
  			cal.set(java.util.Calendar.HOUR_OF_DAY, hour + 1);
  		}
  	}
  
  	/**
  	 * NOT YET IMPLEMENTED: Returns the time before the given time that the
  	 * <code>CronExpression</code> matches.
  	 */
  	public Date getTimeBefore(Date endTime) {
  		// FUTURE_TODO: implement QUARTZ-423
  		return null;
  	}
  
  	/**
  	 * NOT YET IMPLEMENTED: Returns the final time that the <code>CronExpression</code>
  	 * will match.
  	 */
  	public Date getFinalFireTime() {
  		// FUTURE_TODO: implement QUARTZ-423
  		return null;
  	}
  
  	protected boolean isLeapYear(int year) {
  		return ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0));
  	}
  
  	protected int getLastDayOfMonth(int monthNum, int year) {
  
  		switch (monthNum) {
  		case 1:
  			return 31;
  		case 2:
  			return (isLeapYear(year)) ? 29 : 28;
  		case 3:
  			return 31;
  		case 4:
  			return 30;
  		case 5:
  			return 31;
  		case 6:
  			return 30;
  		case 7:
  			return 31;
  		case 8:
  			return 31;
  		case 9:
  			return 30;
  		case 10:
  			return 31;
  		case 11:
  			return 30;
  		case 12:
  			return 31;
  		default:
  			throw new IllegalArgumentException("Illegal month number: " + monthNum);
  		}
  	}
  
  	private void readObject(java.io.ObjectInputStream stream) throws java.io.IOException, ClassNotFoundException {
  
  		stream.defaultReadObject();
  		try {
  			buildExpression(cronExpression);
  		}
  		catch (Exception ignore) {
  		} // never happens
  	}
  
  	@Override
  	@Deprecated
  	public Object clone() {
  		return new CronExpression(this);
  	}
  
  }
  
  class ValueSet {
  
  	public int value;
  
  	public int pos;
  
  }
  