simpledateformat.java

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    return true;
  }


  /**
   * Formats the date input according to the format string in use,
   * appending to the specified StringBuffer.  The input StringBuffer
   * is returned as output for convenience.
   */
  public StringBuffer format(Date date, StringBuffer buffer, FieldPosition pos)
  {
    String temp;
    calendar.setTime(date);
    
    // go through vector, filling in fields where applicable, else toString
    Enumeration e = tokens.elements();
    while (e.hasMoreElements()) {
      Object o = e.nextElement();
      if (o instanceof FieldSizePair) {
	FieldSizePair p = (FieldSizePair) o;
	int beginIndex = buffer.length();
	switch (p.field) {
	case ERA_FIELD:
	  buffer.append(formatData.eras[calendar.get(Calendar.ERA)]);
	  break;
	case YEAR_FIELD:
	  temp = String.valueOf(calendar.get(Calendar.YEAR));
	  if (p.size < 4)
	    buffer.append(temp.substring(temp.length()-2));
	  else
	    buffer.append(temp);
	  break;
	case MONTH_FIELD:
	  if (p.size < 3)
	    withLeadingZeros(calendar.get(Calendar.MONTH)+1,p.size,buffer);
	  else if (p.size < 4) {
		final int month = calendar.get(Calendar.MONTH);
		buffer.append(formatData.shortMonths[month]);
	  }
	  else
	    buffer.append(formatData.months[calendar.get(Calendar.MONTH)]);
	  break;
	case DATE_FIELD:
	  withLeadingZeros(calendar.get(Calendar.DATE),p.size,buffer);
	  break;
	case HOUR_OF_DAY1_FIELD: // 1-24
	  withLeadingZeros(((calendar.get(Calendar.HOUR_OF_DAY)+23)%24)+1,p.size,buffer);
	  break;
	case HOUR_OF_DAY0_FIELD: // 0-23
	  withLeadingZeros(calendar.get(Calendar.HOUR_OF_DAY),p.size,buffer);
	  break;
	case MINUTE_FIELD:
	  withLeadingZeros(calendar.get(Calendar.MINUTE),p.size,buffer);
	  break;
	case SECOND_FIELD:
	  withLeadingZeros(calendar.get(Calendar.SECOND),p.size,buffer);
	  break;
	case MILLISECOND_FIELD:
	  withLeadingZeros(calendar.get(Calendar.MILLISECOND),p.size,buffer);
	  break;
	case DAY_OF_WEEK_FIELD:
	  if (p.size < 4)
	    buffer.append(formatData.shortWeekdays[calendar.get(Calendar.DAY_OF_WEEK)]);
	  else
	    buffer.append(formatData.weekdays[calendar.get(Calendar.DAY_OF_WEEK)]);
	  break;
	case DAY_OF_YEAR_FIELD:
	  withLeadingZeros(calendar.get(Calendar.DAY_OF_YEAR),p.size,buffer);
	  break;
	case DAY_OF_WEEK_IN_MONTH_FIELD:
	  withLeadingZeros(calendar.get(Calendar.DAY_OF_WEEK_IN_MONTH),p.size,buffer);
	  break;
	case WEEK_OF_YEAR_FIELD:
	  withLeadingZeros(calendar.get(Calendar.WEEK_OF_YEAR),p.size,buffer);
	  break;
	case WEEK_OF_MONTH_FIELD:
	  withLeadingZeros(calendar.get(Calendar.WEEK_OF_MONTH),p.size,buffer);
	  break;
	case AM_PM_FIELD:
	  buffer.append(formatData.ampms[calendar.get(Calendar.AM_PM)]);
	  break;
	case HOUR1_FIELD: // 1-12
	  withLeadingZeros(((calendar.get(Calendar.HOUR)+11)%12)+1,p.size,buffer);
	  break;
	case HOUR0_FIELD: // 0-11
	  withLeadingZeros(calendar.get(Calendar.HOUR),p.size,buffer);
	  break;
	case TIMEZONE_FIELD:
	  TimeZone zone = calendar.getTimeZone();
	  boolean isDST = calendar.get(Calendar.DST_OFFSET) != 0;
	  // FIXME: XXX: This should be a localized time zone.
	  String zoneID = zone.getDisplayName(isDST, p.size > 3 ? TimeZone.LONG : TimeZone.SHORT);
	  buffer.append(zoneID);
	  break;
	default:
	  throw new IllegalArgumentException("Illegal pattern character");
	}
	if (pos != null && p.field == pos.getField())
	  {
	    pos.setBeginIndex(beginIndex);
	    pos.setEndIndex(buffer.length());
	  }
      } else {
	buffer.append(o.toString());
      }
    }
    return buffer;
  }

  private void withLeadingZeros(int value, int length, StringBuffer buffer) 
  {
    String valStr = String.valueOf(value);
    for (length -= valStr.length(); length > 0; length--)
      buffer.append('0');
    buffer.append(valStr);
  }

  private final boolean expect (String source, ParsePosition pos, char ch)
  {
    int x = pos.getIndex();
    boolean r = x < source.length() && source.charAt(x) == ch;
    if (r)
      pos.setIndex(x + 1);
    else
      pos.setErrorIndex(x);
    return r;
  }

  /**
   * This method parses the specified string into a date.
   * 
   * @param dateStr The date string to parse.
   * @param pos The input and output parse position
   *
   * @return The parsed date, or <code>null</code> if the string cannot be
   * parsed.
   */
  public Date parse (String dateStr, ParsePosition pos)
  {
    int fmt_index = 0;
    int fmt_max = pattern.length();

    calendar.clear();
    boolean saw_timezone = false;
    int quote_start = -1;
    boolean is2DigitYear = false;
    for (; fmt_index < fmt_max; ++fmt_index)
      {
	char ch = pattern.charAt(fmt_index);
	if (ch == '\'')
	  {
	    int index = pos.getIndex();
	    if (fmt_index < fmt_max - 1
		&& pattern.charAt(fmt_index + 1) == '\'')
	      {
		if (! expect (dateStr, pos, ch))
		  return null;
		++fmt_index;
	      }
	    else
	      quote_start = quote_start < 0 ? fmt_index : -1;
	    continue;
	  }

	if (quote_start != -1
	    || ((ch < 'a' || ch > 'z')
		&& (ch < 'A' || ch > 'Z')))
	  {
	    if (! expect (dateStr, pos, ch))
	      return null;
	    continue;
	  }

	// We've arrived at a potential pattern character in the
	// pattern.
	int first = fmt_index;
	while (++fmt_index < fmt_max && pattern.charAt(fmt_index) == ch)
	  ;
	int fmt_count = fmt_index - first;
	--fmt_index;

	// We can handle most fields automatically: most either are
	// numeric or are looked up in a string vector.  In some cases
	// we need an offset.  When numeric, `offset' is added to the
	// resulting value.  When doing a string lookup, offset is the
	// initial index into the string array.
	int calendar_field;
	boolean is_numeric = true;
	String[] match = null;
	int offset = 0;
	boolean maybe2DigitYear = false;
	switch (ch)
	  {
	  case 'd':
	    calendar_field = Calendar.DATE;
	    break;
	  case 'D':
	    calendar_field = Calendar.DAY_OF_YEAR;
	    break;
	  case 'F':
	    calendar_field = Calendar.DAY_OF_WEEK_IN_MONTH;
	    break;
	  case 'E':
	    is_numeric = false;
	    offset = 1;
	    calendar_field = Calendar.DAY_OF_WEEK;
	    match = (fmt_count <= 3
		     ? formatData.getShortWeekdays()
		     : formatData.getWeekdays());
	    break;
	  case 'w':
	    calendar_field = Calendar.WEEK_OF_YEAR;
	    break;
	  case 'W':
	    calendar_field = Calendar.WEEK_OF_MONTH;
	    break;
	  case 'M':
	    calendar_field = Calendar.MONTH;
	    if (fmt_count <= 2)
	      offset = -1;
	    else
	      {
		is_numeric = false;
		match = (fmt_count <= 3
			 ? formatData.getShortMonths()
			 : formatData.getMonths());
	      }
	    break;
	  case 'y':
	    calendar_field = Calendar.YEAR;
	    if (fmt_count <= 2)
	      maybe2DigitYear = true;
	    break;
	  case 'K':
	    calendar_field = Calendar.HOUR;
	    break;
	  case 'h':
	    calendar_field = Calendar.HOUR;
	    break;
	  case 'H':
	    calendar_field = Calendar.HOUR_OF_DAY;
	    break;
	  case 'k':
	    calendar_field = Calendar.HOUR_OF_DAY;
	    break;
	  case 'm':
	    calendar_field = Calendar.MINUTE;
	    break;
	  case 's':
	    calendar_field = Calendar.SECOND;
	    break;
	  case 'S':
	    calendar_field = Calendar.MILLISECOND;
	    break;
	  case 'a':
	    is_numeric = false;
	    calendar_field = Calendar.AM_PM;
	    match = formatData.getAmPmStrings();
	    break;
	  case 'z':
	    // We need a special case for the timezone, because it
	    // uses a different data structure than the other cases.
	    is_numeric = false;
	    calendar_field = Calendar.DST_OFFSET;
	    String[][] zoneStrings = formatData.getZoneStrings();
	    int zoneCount = zoneStrings.length;
	    int index = pos.getIndex();
	    boolean found_zone = false;
	    for (int j = 0;  j < zoneCount;  j++)
	      {
		String[] strings = zoneStrings[j];
		int k;
		for (k = 1; k < strings.length; ++k)
		  {
		    if (dateStr.startsWith(strings[k], index))
		      break;
		  }
		if (k != strings.length)
		  {
		    found_zone = true;
		    saw_timezone = true;
		    TimeZone tz = TimeZone.getTimeZone (strings[0]);
		    calendar.setTimeZone (tz);
		    calendar.set (Calendar.ZONE_OFFSET, tz.getRawOffset ());
		    offset = 0;
		    if (k > 2 && tz instanceof SimpleTimeZone)
		      {
			SimpleTimeZone stz = (SimpleTimeZone) tz;
			offset = stz.getDSTSavings ();
		      }
		    pos.setIndex(index + strings[k].length());
		    break;
		  }
	      }
	    if (! found_zone)
	      {
		pos.setErrorIndex(pos.getIndex());
		return null;
	      }
	    break;
	  default:
	    pos.setErrorIndex(pos.getIndex());
	    return null;
	  }

	// Compute the value we should assign to the field.
	int value;
	int index = -1;
	if (is_numeric)
	  {
	    numberFormat.setMinimumIntegerDigits(fmt_count);
	    if (maybe2DigitYear)
	      index = pos.getIndex();
	    Number n = numberFormat.parse(dateStr, pos);
	    if (pos == null || ! (n instanceof Long))
	      return null;
	    value = n.intValue() + offset;
	  }
	else if (match != null)
	  {
	    index = pos.getIndex();
	    int i;
	    for (i = offset; i < match.length; ++i)
	      {
		if (dateStr.startsWith(match[i], index))
		  break;
	      }
	    if (i == match.length)
	      {
		pos.setErrorIndex(index);
		return null;
	      }
	    pos.setIndex(index + match[i].length());
	    value = i;
	  }
	else
	  value = offset;
	  
	if (maybe2DigitYear)
	  {
	    // Parse into default century if the numeric year string has 
	    // exactly 2 digits.
	    int digit_count = pos.getIndex() - index;
	    if (digit_count == 2)
	      is2DigitYear = true;
	  }

	// Assign the value and move on.
	calendar.set(calendar_field, value);
      }
    
    if (is2DigitYear)
      {
	// Apply the 80-20 heuristic to dermine the full year based on 
	// defaultCenturyStart. 
	int year = defaultCentury + calendar.get(Calendar.YEAR);
	calendar.set(Calendar.YEAR, year);
	if (calendar.getTime().compareTo(defaultCenturyStart) < 0)
	  calendar.set(Calendar.YEAR, year + 100);      
      }

    try
      {
	if (! saw_timezone)
	  {
	    // Use the real rules to determine whether or not this
	    // particular time is in daylight savings.
	    calendar.clear (Calendar.DST_OFFSET);
	    calendar.clear (Calendar.ZONE_OFFSET);
	  }
        return calendar.getTime();
      }
    catch (IllegalArgumentException x)
      {
        pos.setErrorIndex(pos.getIndex());
	return null;
      }
  }

  // Compute the start of the current century as defined by
  // get2DigitYearStart.
  private void computeCenturyStart()
  {
    int year = calendar.get(Calendar.YEAR);
    calendar.set(Calendar.YEAR, year - 80);
    set2DigitYearStart(calendar.getTime());
  }
}