Date validation

/**
	 * Validate whether the argument string can be parsed into a 
	 * legal date.<br />
	 * 
	 * Does check for formating errors and illegal data (so an invalid
	 * month or day number is detected).
	 * @param allowPast set to true to allow dates in the past, false if
	 * only dates in the future should be allowed.
	 * @param formatStr date format string to be used to validate against
	 * @return true if a correct date and conforms to the restrictions
	 */
	public static boolean validateDate(String dateStr, 
										boolean allowPast, 
										String formatStr)
	{
                         if (formatStr == null) return false; // or throw some kinda exception, possibly a InvalidArgumentException
		SimpleDateFormat df = new SimpleDateFormat(formatStr);
		Date testDate = null;
		try
		{
			testDate = df.parse(dateStr);
		}
		catch (ParseException e)
		{
			// invalid date format
			return false;
		}
		if (!allowPast)
		{
			// initialise the calendar to midnight to prevent 
			// the current day from being rejected
			Calendar cal = Calendar.getInstance();
			cal.set(Calendar.HOUR_OF_DAY, 0);
			cal.set(Calendar.MINUTE, 0);
			cal.set(Calendar.SECOND, 0);
			cal.set(Calendar.MILLISECOND, 0);
			if (cal.getTime().after(testDate)) return false;
		}
		// now test for legal values of parameters
		if (!df.format(testDate).equals(dateStr)) return false;
		return true;
	}