timezone.java

gcc的组建

   */
  public abstract int getOffset(int era, int year, int month,
				int day, int dayOfWeek, int milliseconds);

  /**
   * Get the time zone offset for the specified date, modified in case of
   * daylight savings.  This is the offset to add to UTC to get the local
   * time.
   * @param date the date represented in millisecends
   * since January 1, 1970 00:00:00 GMT.
   * @since 1.4
   */
  public int getOffset(long date)
  {
    return (inDaylightTime(new Date(date))
            ? getRawOffset() + getDSTSavings()
            : getRawOffset());
  }
  
  /**
   * Gets the time zone offset, ignoring daylight savings.  This is
   * the offset to add to UTC to get the local time.
   * @return the time zone offset in milliseconds.  
   */
  public abstract int getRawOffset();

  /**
   * Sets the time zone offset, ignoring daylight savings.  This is
   * the offset to add to UTC to get the local time.
   * @param offsetMillis the time zone offset to GMT.
   */
  public abstract void setRawOffset(int offsetMillis);

  /**
   * Gets the identifier of this time zone. For instance, PST for
   * Pacific Standard Time.
   * @returns the ID of this time zone.  
   */
  public String getID()
  {
    return ID;
  }

  /**
   * Sets the identifier of this time zone. For instance, PST for
   * Pacific Standard Time.
   * @param id the new time zone ID.
   * @throws NullPointerException if <code>id</code> is <code>null</code>
   */
  public void setID(String id)
  {
    if (id == null)
      throw new NullPointerException();
    
    this.ID = id;
  }

  /**
   * This method returns a string name of the time zone suitable
   * for displaying to the user.  The string returned will be the long
   * description of the timezone in the current locale.  The name
   * displayed will assume daylight savings time is not in effect.
   *
   * @return The name of the time zone.
   */
  public final String getDisplayName()
  {
    return (getDisplayName(false, LONG, Locale.getDefault()));
  }

  /**
   * This method returns a string name of the time zone suitable
   * for displaying to the user.  The string returned will be the long
   * description of the timezone in the specified locale. The name
   * displayed will assume daylight savings time is not in effect.
   *
   * @param locale The locale for this timezone name.
   *
   * @return The name of the time zone.
   */
  public final String getDisplayName(Locale locale)
  {
    return (getDisplayName(false, LONG, locale));
  }

  /**
   * This method returns a string name of the time zone suitable
   * for displaying to the user.  The string returned will be of the
   * specified type in the current locale. 
   *
   * @param dst Whether or not daylight savings time is in effect.
   * @param style <code>LONG</code> for a long name, <code>SHORT</code> for
   * a short abbreviation.
   *
   * @return The name of the time zone.
   */
  public final String getDisplayName(boolean dst, int style)
  {
    return (getDisplayName(dst, style, Locale.getDefault()));
  }


  /**
   * This method returns a string name of the time zone suitable
   * for displaying to the user.  The string returned will be of the
   * specified type in the specified locale. 
   *
   * @param dst Whether or not daylight savings time is in effect.
   * @param style <code>LONG</code> for a long name, <code>SHORT</code> for
   * a short abbreviation.
   * @param locale The locale for this timezone name.
   *
   * @return The name of the time zone.
   */
  public String getDisplayName(boolean dst, int style, Locale locale)
  {
    DateFormatSymbols dfs;
    try
      {
	dfs = new DateFormatSymbols(locale);

	// The format of the value returned is defined by us.
	String[][]zoneinfo = dfs.getZoneStrings();
	for (int i = 0; i < zoneinfo.length; i++)
	  {
	    if (zoneinfo[i][0].equals(getID()))
	      {
		if (!dst)
		  {
		    if (style == SHORT)
		      return (zoneinfo[i][2]);
		    else
		      return (zoneinfo[i][1]);
		  }
		else
		  {
		    if (style == SHORT)
		      return (zoneinfo[i][4]);
		    else
		      return (zoneinfo[i][3]);
		  }
	      }
	  }
      }
    catch (MissingResourceException e)
      {
      }

    return getDefaultDisplayName(dst);
  }

  private String getDefaultDisplayName(boolean dst)
  {
    int offset = getRawOffset();
    if (dst && this instanceof SimpleTimeZone)
      {
	// ugly, but this is a design failure of the API:
	// getDisplayName takes a dst parameter even though
	// TimeZone knows nothing about daylight saving offsets.
	offset += ((SimpleTimeZone) this).getDSTSavings();
      }

    StringBuffer sb = new StringBuffer(9);
    sb.append("GMT");

    offset = offset / (1000 * 60);
    int hours = Math.abs(offset) / 60;
    int minutes = Math.abs(offset) % 60;

    if (minutes != 0 || hours != 0)
      {
	sb.append(offset >= 0 ? '+' : '-');
	sb.append((char) ('0' + hours / 10));
	sb.append((char) ('0' + hours % 10));
	sb.append(':');
	sb.append((char) ('0' + minutes / 10));
	sb.append((char) ('0' + minutes % 10));
      }

    return sb.toString();
  }

  /** 
   * Returns true, if this time zone uses Daylight Savings Time.
   */
  public abstract boolean useDaylightTime();

  /**
   * Returns true, if the given date is in Daylight Savings Time in this
   * time zone.
   * @param date the given Date.
   */
  public abstract boolean inDaylightTime(Date date);

  /**
   * Gets the daylight savings offset.  This is a positive offset in
   * milliseconds with respect to standard time.  Typically this
   * is one hour, but for some time zones this may be half an our.
   * <p>The default implementation returns 3600000 milliseconds
   * (one hour) if the time zone uses daylight savings time
   * (as specified by {@link #useDaylightTime()}), otherwise
   * it returns 0.
   * @return the daylight savings offset in milliseconds.
   * @since 1.4
   */
  public int getDSTSavings ()
  {
    return useDaylightTime () ? 3600000 : 0;
  }

  /**
   * Gets the TimeZone for the given ID.
   * @param ID the time zone identifier.
   * @return The time zone for the identifier or GMT, if no such time
   * zone exists.
   */
  // FIXME: XXX: JCL indicates this and other methods are synchronized.
  public static TimeZone getTimeZone(String ID)
  {
    // First check timezones hash
    TimeZone tz = (TimeZone) timezones().get(ID);
    if (tz != null)
      {
	if (tz.getID().equals(ID))
	  return tz;

	// We always return a timezone with the requested ID.
	// This is the same behaviour as with JDK1.2.
	tz = (TimeZone) tz.clone();
	tz.setID(ID);
	// We also save the alias, so that we return the same
	// object again if getTimeZone is called with the same
	// alias.
	timezones().put(ID, tz);
	return tz;
      }

    // See if the ID is really a GMT offset form.
    // Note that GMT is in the table so we know it is different.
    if (ID.startsWith("GMT"))
      {
	int pos = 3;
	int offset_direction = 1;

	if (ID.charAt(pos) == '-')
	  {
	    offset_direction = -1;
	    pos++;
	  }
	else if (ID.charAt(pos) == '+')
	  {
	    pos++;
	  }

	try
	  {
	    int hour, minute;

	    String offset_str = ID.substring(pos);
	    int idx = offset_str.indexOf(":");
	    if (idx != -1)
	      {
		hour = Integer.parseInt(offset_str.substring(0, idx));
		minute = Integer.parseInt(offset_str.substring(idx + 1));
	      }
	    else
	      {
		int offset_length = offset_str.length();
		if (offset_length <= 2)
		  {
		    // Only hour
		    hour = Integer.parseInt(offset_str);
		    minute = 0;
		  }
		else
		  {
		    // hour and minute, not separated by colon
		    hour = Integer.parseInt
		      (offset_str.substring(0, offset_length - 2));
		    minute = Integer.parseInt
		      (offset_str.substring(offset_length - 2));
		  }
	      }

	    return new SimpleTimeZone((hour * (60 * 60 * 1000) +
				       minute * (60 * 1000))
				      * offset_direction, ID);
	  }
	catch (NumberFormatException e)
	  {
	  }
      }

    // Finally, return GMT per spec
    return getTimeZone("GMT");
  }

  /**
   * Gets the available IDs according to the given time zone
   * offset.  
   * @param rawOffset the given time zone GMT offset.
   * @return An array of IDs, where the time zone has the specified GMT
   * offset. For example <code>{"Phoenix", "Denver"}</code>, since both have
   * GMT-07:00, but differ in daylight savings behaviour.
   */
  public static String[] getAvailableIDs(int rawOffset)
  {
    int count = 0;
    Iterator iter = timezones().entrySet().iterator();
    while (iter.hasNext())
      {
	// Don't iterate the values, since we want to count 
	// doubled values (aliases)
	Map.Entry entry = (Map.Entry) iter.next();
	if (((TimeZone) entry.getValue()).getRawOffset() == rawOffset)
	  count++;
      }

    String[] ids = new String[count];
    count = 0;
    iter = timezones().entrySet().iterator();
    while (iter.hasNext())
      {
	Map.Entry entry = (Map.Entry) iter.next();
	if (((TimeZone) entry.getValue()).getRawOffset() == rawOffset)
	  ids[count++] = (String) entry.getKey();
      }
    return ids;
  }

  /**
   * Gets all available IDs.
   * @return An array of all supported IDs.
   */
  public static String[] getAvailableIDs()
  {
    return (String[])
      timezones().keySet().toArray(new String[timezones().size()]);
  }

  /**
   * Returns the time zone under which the host is running.  This
   * can be changed with setDefault.
   *
   * @return A clone of the current default time zone for this host.
   * @see #setDefault
   */
  public static TimeZone getDefault()
  {
    return (TimeZone) defaultZone().clone();
  }

  public static void setDefault(TimeZone zone)
  {
    // Hmmmm. No Security checks?
    defaultZone0 = zone;
  }

  /**
   * Test if the other time zone uses the same rule and only
   * possibly differs in ID.  This implementation for this particular
   * class will return true if the raw offsets are identical.  Subclasses
   * should override this method if they use daylight savings.
   * @return true if this zone has the same raw offset
   */
  public boolean hasSameRules(TimeZone other)
  {
    return other.getRawOffset() == getRawOffset();
  }

  /**
   * Returns a clone of this object.  I can't imagine, why this is
   * useful for a time zone.
   */
  public Object clone()
  {
    try
      {
	return super.clone();
      }
    catch (CloneNotSupportedException ex)
      {
	return null;
      }
  }
}