1 /*
2 * Copyright (c) 1996, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 /*
27 * (C) Copyright Taligent, Inc. 1996 - All Rights Reserved
28 * (C) Copyright IBM Corp. 1996 - All Rights Reserved
29 *
30 * The original version of this source code and documentation is copyrighted
31 * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
32 * materials are provided under terms of a License Agreement between Taligent
33 * and Sun. This technology is protected by multiple US and International
34 * patents. This notice and attribution to Taligent may not be removed.
35 * Taligent is a registered trademark of Taligent, Inc.
36 *
37 */
38
39 package java.util;
40
41 import java.io.Serializable;
42 import java.time.ZoneId;
43
44 import jdk.internal.util.StaticProperty;
45 import sun.security.action.GetPropertyAction;
46 import sun.util.calendar.ZoneInfo;
47 import sun.util.calendar.ZoneInfoFile;
48 import sun.util.locale.provider.TimeZoneNameUtility;
49
50 /**
51 * <code>TimeZone</code> represents a time zone offset, and also figures out daylight
52 * savings.
53 *
54 * <p>
55 * Typically, you get a <code>TimeZone</code> using <code>getDefault</code>
56 * which creates a <code>TimeZone</code> based on the time zone where the program
57 * is running. For example, for a program running in Japan, <code>getDefault</code>
58 * creates a <code>TimeZone</code> object based on Japanese Standard Time.
59 *
60 * <p>
61 * You can also get a <code>TimeZone</code> using <code>getTimeZone</code>
62 * along with a time zone ID. For instance, the time zone ID for the
63 * U.S. Pacific Time zone is "America/Los_Angeles". So, you can get a
64 * U.S. Pacific Time <code>TimeZone</code> object with:
65 * <blockquote><pre>
66 * TimeZone tz = TimeZone.getTimeZone("America/Los_Angeles");
67 * </pre></blockquote>
68 * You can use the <code>getAvailableIDs</code> method to iterate through
69 * all the supported time zone IDs. You can then choose a
70 * supported ID to get a <code>TimeZone</code>.
71 * If the time zone you want is not represented by one of the
72 * supported IDs, then a custom time zone ID can be specified to
73 * produce a TimeZone. The syntax of a custom time zone ID is:
74 *
75 * <blockquote><pre>
76 * <a id="CustomID"><i>CustomID:</i></a>
77 * <code>GMT</code> <i>Sign</i> <i>Hours</i> <code>:</code> <i>Minutes</i>
78 * <code>GMT</code> <i>Sign</i> <i>Hours</i> <i>Minutes</i>
79 * <code>GMT</code> <i>Sign</i> <i>Hours</i>
80 * <i>Sign:</i> one of
81 * <code>+ -</code>
82 * <i>Hours:</i>
83 * <i>Digit</i>
84 * <i>Digit</i> <i>Digit</i>
85 * <i>Minutes:</i>
86 * <i>Digit</i> <i>Digit</i>
87 * <i>Digit:</i> one of
88 * <code>0 1 2 3 4 5 6 7 8 9</code>
89 * </pre></blockquote>
90 *
91 * <i>Hours</i> must be between 0 to 23 and <i>Minutes</i> must be
92 * between 00 to 59. For example, "GMT+10" and "GMT+0010" mean ten
93 * hours and ten minutes ahead of GMT, respectively.
94 * <p>
95 * The format is locale independent and digits must be taken from the
96 * Basic Latin block of the Unicode standard. No daylight saving time
97 * transition schedule can be specified with a custom time zone ID. If
98 * the specified string doesn't match the syntax, <code>"GMT"</code>
99 * is used.
100 * <p>
101 * When creating a <code>TimeZone</code>, the specified custom time
102 * zone ID is normalized in the following syntax:
103 * <blockquote><pre>
104 * <a id="NormalizedCustomID"><i>NormalizedCustomID:</i></a>
105 * <code>GMT</code> <i>Sign</i> <i>TwoDigitHours</i> <code>:</code> <i>Minutes</i>
106 * <i>Sign:</i> one of
107 * <code>+ -</code>
108 * <i>TwoDigitHours:</i>
109 * <i>Digit</i> <i>Digit</i>
110 * <i>Minutes:</i>
111 * <i>Digit</i> <i>Digit</i>
112 * <i>Digit:</i> one of
113 * <code>0 1 2 3 4 5 6 7 8 9</code>
114 * </pre></blockquote>
115 * For example, TimeZone.getTimeZone("GMT-8").getID() returns "GMT-08:00".
116 *
117 * <h2>Three-letter time zone IDs</h2>
118 *
119 * For compatibility with JDK 1.1.x, some other three-letter time zone IDs
120 * (such as "PST", "CTT", "AST") are also supported. However, <strong>their
121 * use is deprecated</strong> because the same abbreviation is often used
122 * for multiple time zones (for example, "CST" could be U.S. "Central Standard
123 * Time" and "China Standard Time"), and the Java platform can then only
124 * recognize one of them.
125 *
126 *
127 * @see Calendar
128 * @see GregorianCalendar
129 * @see SimpleTimeZone
130 * @author Mark Davis, David Goldsmith, Chen-Lieh Huang, Alan Liu
131 * @since 1.1
132 */
133 public abstract class TimeZone implements Serializable, Cloneable {
134 /**
135 * Sole constructor. (For invocation by subclass constructors, typically
136 * implicit.)
137 */
138 public TimeZone() {
139 }
140
141 /**
142 * A style specifier for <code>getDisplayName()</code> indicating
143 * a short name, such as "PST."
144 * @see #LONG
145 * @since 1.2
146 */
147 public static final int SHORT = 0;
148
149 /**
150 * A style specifier for <code>getDisplayName()</code> indicating
151 * a long name, such as "Pacific Standard Time."
152 * @see #SHORT
153 * @since 1.2
154 */
155 public static final int LONG = 1;
156
157 // Constants used internally; unit is milliseconds
158 private static final int ONE_MINUTE = 60*1000;
159 private static final int ONE_HOUR = 60*ONE_MINUTE;
160 private static final int ONE_DAY = 24*ONE_HOUR;
161
162 // Proclaim serialization compatibility with JDK 1.1
163 @java.io.Serial
164 static final long serialVersionUID = 3581463369166924961L;
165
166 /**
167 * Gets the time zone offset, for current date, modified in case of
168 * daylight savings. This is the offset to add to UTC to get local time.
169 * <p>
170 * This method returns a historically correct offset if an
171 * underlying <code>TimeZone</code> implementation subclass
172 * supports historical Daylight Saving Time schedule and GMT
173 * offset changes.
174 *
175 * @param era the era of the given date.
176 * @param year the year in the given date.
177 * @param month the month in the given date.
178 * Month is 0-based. e.g., 0 for January.
179 * @param day the day-in-month of the given date.
180 * @param dayOfWeek the day-of-week of the given date.
181 * @param milliseconds the milliseconds in day in <em>standard</em>
182 * local time.
183 *
184 * @return the offset in milliseconds to add to GMT to get local time.
185 *
186 * @see Calendar#ZONE_OFFSET
187 * @see Calendar#DST_OFFSET
188 */
189 public abstract int getOffset(int era, int year, int month, int day,
190 int dayOfWeek, int milliseconds);
191
192 /**
193 * Returns the offset of this time zone from UTC at the specified
194 * date. If Daylight Saving Time is in effect at the specified
195 * date, the offset value is adjusted with the amount of daylight
196 * saving.
197 * <p>
198 * This method returns a historically correct offset value if an
199 * underlying TimeZone implementation subclass supports historical
200 * Daylight Saving Time schedule and GMT offset changes.
201 *
202 * @param date the date represented in milliseconds since January 1, 1970 00:00:00 GMT
203 * @return the amount of time in milliseconds to add to UTC to get local time.
204 *
205 * @see Calendar#ZONE_OFFSET
206 * @see Calendar#DST_OFFSET
207 * @since 1.4
208 */
209 public int getOffset(long date) {
210 if (inDaylightTime(new Date(date))) {
211 return getRawOffset() + getDSTSavings();
212 }
213 return getRawOffset();
214 }
215
216 /**
217 * Gets the raw GMT offset and the amount of daylight saving of this
218 * time zone at the given time.
219 * @param date the milliseconds (since January 1, 1970,
220 * 00:00:00.000 GMT) at which the time zone offset and daylight
221 * saving amount are found
222 * @param offsets an array of int where the raw GMT offset
223 * (offset[0]) and daylight saving amount (offset[1]) are stored,
224 * or null if those values are not needed. The method assumes that
225 * the length of the given array is two or larger.
226 * @return the total amount of the raw GMT offset and daylight
227 * saving at the specified date.
228 *
229 * @see Calendar#ZONE_OFFSET
230 * @see Calendar#DST_OFFSET
231 */
232 int getOffsets(long date, int[] offsets) {
233 int rawoffset = getRawOffset();
234 int dstoffset = 0;
235 if (inDaylightTime(new Date(date))) {
236 dstoffset = getDSTSavings();
237 }
238 if (offsets != null) {
239 offsets[0] = rawoffset;
240 offsets[1] = dstoffset;
241 }
242 return rawoffset + dstoffset;
243 }
244
245 /**
246 * Sets the base time zone offset to GMT.
247 * This is the offset to add to UTC to get local time.
248 * <p>
249 * If an underlying <code>TimeZone</code> implementation subclass
250 * supports historical GMT offset changes, the specified GMT
251 * offset is set as the latest GMT offset and the difference from
252 * the known latest GMT offset value is used to adjust all
253 * historical GMT offset values.
254 *
255 * @param offsetMillis the given base time zone offset to GMT.
256 */
257 public abstract void setRawOffset(int offsetMillis);
258
259 /**
260 * Returns the amount of time in milliseconds to add to UTC to get
261 * standard time in this time zone. Because this value is not
262 * affected by daylight saving time, it is called <I>raw
263 * offset</I>.
264 * <p>
265 * If an underlying <code>TimeZone</code> implementation subclass
266 * supports historical GMT offset changes, the method returns the
267 * raw offset value of the current date. In Honolulu, for example,
268 * its raw offset changed from GMT-10:30 to GMT-10:00 in 1947, and
269 * this method always returns -36000000 milliseconds (i.e., -10
270 * hours).
271 *
272 * @return the amount of raw offset time in milliseconds to add to UTC.
273 * @see Calendar#ZONE_OFFSET
274 */
275 public abstract int getRawOffset();
276
277 /**
278 * Gets the ID of this time zone.
279 * @return the ID of this time zone.
280 */
281 public String getID()
282 {
283 return ID;
284 }
285
286 /**
287 * Sets the time zone ID. This does not change any other data in
288 * the time zone object.
289 * @param ID the new time zone ID.
290 */
291 public void setID(String ID)
292 {
293 if (ID == null) {
294 throw new NullPointerException();
295 }
296 this.ID = ID;
297 this.zoneId = null; // invalidate cache
298 }
299
300 /**
301 * Returns a long standard time name of this {@code TimeZone} suitable for
302 * presentation to the user in the default locale.
303 *
304 * <p>This method is equivalent to:
305 * <blockquote><pre>
306 * getDisplayName(false, {@link #LONG},
307 * Locale.getDefault({@link Locale.Category#DISPLAY}))
308 * </pre></blockquote>
309 *
310 * @return the human-readable name of this time zone in the default locale.
311 * @since 1.2
312 * @see #getDisplayName(boolean, int, Locale)
313 * @see Locale#getDefault(Locale.Category)
314 * @see Locale.Category
315 */
316 public final String getDisplayName() {
317 return getDisplayName(false, LONG,
318 Locale.getDefault(Locale.Category.DISPLAY));
319 }
320
321 /**
322 * Returns a long standard time name of this {@code TimeZone} suitable for
323 * presentation to the user in the specified {@code locale}.
324 *
325 * <p>This method is equivalent to:
326 * <blockquote><pre>
327 * getDisplayName(false, {@link #LONG}, locale)
328 * </pre></blockquote>
329 *
330 * @param locale the locale in which to supply the display name.
331 * @return the human-readable name of this time zone in the given locale.
332 * @exception NullPointerException if {@code locale} is {@code null}.
333 * @since 1.2
334 * @see #getDisplayName(boolean, int, Locale)
335 */
336 public final String getDisplayName(Locale locale) {
337 return getDisplayName(false, LONG, locale);
338 }
339
340 /**
341 * Returns a name in the specified {@code style} of this {@code TimeZone}
342 * suitable for presentation to the user in the default locale. If the
343 * specified {@code daylight} is {@code true}, a Daylight Saving Time name
344 * is returned (even if this {@code TimeZone} doesn't observe Daylight Saving
345 * Time). Otherwise, a Standard Time name is returned.
346 *
347 * <p>This method is equivalent to:
348 * <blockquote><pre>
349 * getDisplayName(daylight, style,
350 * Locale.getDefault({@link Locale.Category#DISPLAY}))
351 * </pre></blockquote>
352 *
353 * @param daylight {@code true} specifying a Daylight Saving Time name, or
354 * {@code false} specifying a Standard Time name
355 * @param style either {@link #LONG} or {@link #SHORT}
356 * @return the human-readable name of this time zone in the default locale.
357 * @exception IllegalArgumentException if {@code style} is invalid.
358 * @since 1.2
359 * @see #getDisplayName(boolean, int, Locale)
360 * @see Locale#getDefault(Locale.Category)
361 * @see Locale.Category
362 * @see java.text.DateFormatSymbols#getZoneStrings()
363 */
364 public final String getDisplayName(boolean daylight, int style) {
365 return getDisplayName(daylight, style,
366 Locale.getDefault(Locale.Category.DISPLAY));
367 }
368
369 /**
370 * Returns a name in the specified {@code style} of this {@code TimeZone}
371 * suitable for presentation to the user in the specified {@code
372 * locale}. If the specified {@code daylight} is {@code true}, a Daylight
373 * Saving Time name is returned (even if this {@code TimeZone} doesn't
374 * observe Daylight Saving Time). Otherwise, a Standard Time name is
375 * returned.
376 *
377 * <p>When looking up a time zone name, the {@linkplain
378 * ResourceBundle.Control#getCandidateLocales(String,Locale) default
379 * <code>Locale</code> search path of <code>ResourceBundle</code>} derived
380 * from the specified {@code locale} is used. (No {@linkplain
381 * ResourceBundle.Control#getFallbackLocale(String,Locale) fallback
382 * <code>Locale</code>} search is performed.) If a time zone name in any
383 * {@code Locale} of the search path, including {@link Locale#ROOT}, is
384 * found, the name is returned. Otherwise, a string in the
385 * <a href="#NormalizedCustomID">normalized custom ID format</a> is returned.
386 *
387 * @param daylight {@code true} specifying a Daylight Saving Time name, or
388 * {@code false} specifying a Standard Time name
389 * @param style either {@link #LONG} or {@link #SHORT}
390 * @param locale the locale in which to supply the display name.
391 * @return the human-readable name of this time zone in the given locale.
392 * @exception IllegalArgumentException if {@code style} is invalid.
393 * @exception NullPointerException if {@code locale} is {@code null}.
394 * @since 1.2
395 * @see java.text.DateFormatSymbols#getZoneStrings()
396 */
397 public String getDisplayName(boolean daylight, int style, Locale locale) {
398 if (style != SHORT && style != LONG) {
399 throw new IllegalArgumentException("Illegal style: " + style);
400 }
401 String id = getID();
402 String name = TimeZoneNameUtility.retrieveDisplayName(id, daylight, style, locale);
403 if (name != null) {
404 return name;
405 }
406
407 if (id.startsWith("GMT") && id.length() > 3) {
408 char sign = id.charAt(3);
409 if (sign == '+' || sign == '-') {
410 return id;
411 }
412 }
413 int offset = getRawOffset();
414 if (daylight) {
415 offset += getDSTSavings();
416 }
417 return ZoneInfoFile.toCustomID(offset);
418 }
419
420 private static String[] getDisplayNames(String id, Locale locale) {
421 return TimeZoneNameUtility.retrieveDisplayNames(id, locale);
422 }
423
424 /**
425 * Returns the amount of time to be added to local standard time
426 * to get local wall clock time.
427 *
428 * <p>The default implementation returns 3600000 milliseconds
429 * (i.e., one hour) if a call to {@link #useDaylightTime()}
430 * returns {@code true}. Otherwise, 0 (zero) is returned.
431 *
432 * <p>If an underlying {@code TimeZone} implementation subclass
433 * supports historical and future Daylight Saving Time schedule
434 * changes, this method returns the amount of saving time of the
435 * last known Daylight Saving Time rule that can be a future
436 * prediction.
437 *
438 * <p>If the amount of saving time at any given time stamp is
439 * required, construct a {@link Calendar} with this {@code
440 * TimeZone} and the time stamp, and call {@link Calendar#get(int)
441 * Calendar.get}{@code (}{@link Calendar#DST_OFFSET}{@code )}.
442 *
443 * @return the amount of saving time in milliseconds
444 * @since 1.4
445 * @see #inDaylightTime(Date)
446 * @see #getOffset(long)
447 * @see #getOffset(int,int,int,int,int,int)
448 * @see Calendar#ZONE_OFFSET
449 */
450 public int getDSTSavings() {
451 if (useDaylightTime()) {
452 return 3600000;
453 }
454 return 0;
455 }
456
457 /**
458 * Queries if this {@code TimeZone} uses Daylight Saving Time.
459 *
460 * <p>If an underlying {@code TimeZone} implementation subclass
461 * supports historical and future Daylight Saving Time schedule
462 * changes, this method refers to the last known Daylight Saving Time
463 * rule that can be a future prediction and may not be the same as
464 * the current rule. Consider calling {@link #observesDaylightTime()}
465 * if the current rule should also be taken into account.
466 *
467 * @return {@code true} if this {@code TimeZone} uses Daylight Saving Time,
468 * {@code false}, otherwise.
469 * @see #inDaylightTime(Date)
470 * @see Calendar#DST_OFFSET
471 */
472 public abstract boolean useDaylightTime();
473
474 /**
475 * Returns {@code true} if this {@code TimeZone} is currently in
476 * Daylight Saving Time, or if a transition from Standard Time to
477 * Daylight Saving Time occurs at any future time.
478 *
479 * <p>The default implementation returns {@code true} if
480 * {@code useDaylightTime()} or {@code inDaylightTime(new Date())}
481 * returns {@code true}.
482 *
483 * @return {@code true} if this {@code TimeZone} is currently in
484 * Daylight Saving Time, or if a transition from Standard Time to
485 * Daylight Saving Time occurs at any future time; {@code false}
486 * otherwise.
487 * @since 1.7
488 * @see #useDaylightTime()
489 * @see #inDaylightTime(Date)
490 * @see Calendar#DST_OFFSET
491 */
492 public boolean observesDaylightTime() {
493 return useDaylightTime() || inDaylightTime(new Date());
494 }
495
496 /**
497 * Queries if the given {@code date} is in Daylight Saving Time in
498 * this time zone.
499 *
500 * @param date the given Date.
501 * @return {@code true} if the given date is in Daylight Saving Time,
502 * {@code false}, otherwise.
503 */
504 public abstract boolean inDaylightTime(Date date);
505
506 /**
507 * Gets the <code>TimeZone</code> for the given ID.
508 *
509 * @param ID the ID for a <code>TimeZone</code>, either an abbreviation
510 * such as "PST", a full name such as "America/Los_Angeles", or a custom
511 * ID such as "GMT-8:00". Note that the support of abbreviations is
512 * for JDK 1.1.x compatibility only and full names should be used.
513 *
514 * @return the specified <code>TimeZone</code>, or the GMT zone if the given ID
515 * cannot be understood.
516 */
517 public static synchronized TimeZone getTimeZone(String ID) {
518 return getTimeZone(ID, true);
519 }
520
521 /**
522 * Gets the {@code TimeZone} for the given {@code zoneId}.
523 *
524 * @param zoneId a {@link ZoneId} from which the time zone ID is obtained
525 * @return the specified {@code TimeZone}, or the GMT zone if the given ID
526 * cannot be understood.
527 * @throws NullPointerException if {@code zoneId} is {@code null}
528 * @since 1.8
529 */
530 public static TimeZone getTimeZone(ZoneId zoneId) {
531 String tzid = zoneId.getId(); // throws an NPE if null
532 char c = tzid.charAt(0);
533 if (c == '+' || c == '-') {
534 tzid = "GMT" + tzid;
535 } else if (c == 'Z' && tzid.length() == 1) {
536 tzid = "UTC";
537 }
538 return getTimeZone(tzid, true);
539 }
540
541 /**
542 * Converts this {@code TimeZone} object to a {@code ZoneId}.
543 *
544 * @return a {@code ZoneId} representing the same time zone as this
545 * {@code TimeZone}
546 * @since 1.8
547 */
548 public ZoneId toZoneId() {
549 ZoneId zId = zoneId;
550 if (zId == null) {
551 zoneId = zId = toZoneId0();
552 }
553 return zId;
554 }
555
556 private ZoneId toZoneId0() {
557 String id = getID();
558 TimeZone defaultZone = defaultTimeZone;
559 // are we not defaultTimeZone but our id is equal to default's?
560 if (defaultZone != this &&
561 defaultZone != null && id.equals(defaultZone.getID())) {
562 // delegate to default TZ which is effectively immutable
563 return defaultZone.toZoneId();
564 }
565 // derive it ourselves
566 if (ZoneInfoFile.useOldMapping() && id.length() == 3) {
567 if ("EST".equals(id))
568 return ZoneId.of("America/New_York");
569 if ("MST".equals(id))
570 return ZoneId.of("America/Denver");
571 if ("HST".equals(id))
572 return ZoneId.of("America/Honolulu");
573 }
574 return ZoneId.of(id, ZoneId.SHORT_IDS);
575 }
576
577 private static TimeZone getTimeZone(String ID, boolean fallback) {
578 TimeZone tz = ZoneInfo.getTimeZone(ID);
579 if (tz == null) {
580 tz = parseCustomTimeZone(ID);
581 if (tz == null && fallback) {
582 tz = new ZoneInfo(GMT_ID, 0);
583 }
584 }
585 return tz;
586 }
587
588 /**
589 * Gets the available IDs according to the given time zone offset in milliseconds.
590 *
591 * @param rawOffset the given time zone GMT offset in milliseconds.
592 * @return an array of IDs, where the time zone for that ID has
593 * the specified GMT offset. For example, "America/Phoenix" and "America/Denver"
594 * both have GMT-07:00, but differ in daylight saving behavior.
595 * @see #getRawOffset()
596 */
597 public static synchronized String[] getAvailableIDs(int rawOffset) {
598 return ZoneInfo.getAvailableIDs(rawOffset);
599 }
600
601 /**
602 * Gets all the available IDs supported.
603 * @return an array of IDs.
604 */
605 public static synchronized String[] getAvailableIDs() {
606 return ZoneInfo.getAvailableIDs();
607 }
608
609 /**
610 * Gets the platform defined TimeZone ID.
611 **/
612 private static native String getSystemTimeZoneID(String javaHome);
613
614 /**
615 * Gets the custom time zone ID based on the GMT offset of the
616 * platform. (e.g., "GMT+08:00")
617 */
618 private static native String getSystemGMTOffsetID();
619
620 /**
621 * Gets the default {@code TimeZone} of the Java virtual machine. If the
622 * cached default {@code TimeZone} is available, its clone is returned.
623 * Otherwise, the method takes the following steps to determine the default
624 * time zone.
625 *
626 * <ul>
627 * <li>Use the {@code user.timezone} property value as the default
628 * time zone ID if it's available.</li>
629 * <li>Detect the platform time zone ID. The source of the
630 * platform time zone and ID mapping may vary with implementation.</li>
631 * <li>Use {@code GMT} as the last resort if the given or detected
632 * time zone ID is unknown.</li>
633 * </ul>
634 *
635 * <p>The default {@code TimeZone} created from the ID is cached,
636 * and its clone is returned. The {@code user.timezone} property
637 * value is set to the ID upon return.
638 *
639 * @return the default {@code TimeZone}
640 * @see #setDefault(TimeZone)
641 */
642 public static TimeZone getDefault() {
643 return (TimeZone) getDefaultRef().clone();
644 }
645
646 /**
647 * Returns the reference to the default TimeZone object. This
648 * method doesn't create a clone.
649 */
650 static TimeZone getDefaultRef() {
651 TimeZone defaultZone = defaultTimeZone;
652 if (defaultZone == null) {
653 // Need to initialize the default time zone.
654 defaultZone = setDefaultZone();
655 assert defaultZone != null;
656 }
657 // Don't clone here.
658 return defaultZone;
659 }
660
661 private static synchronized TimeZone setDefaultZone() {
662 TimeZone tz;
663 // get the time zone ID from the system properties
664 Properties props = GetPropertyAction.privilegedGetProperties();
665 String zoneID = props.getProperty("user.timezone");
666
667 // if the time zone ID is not set (yet), perform the
668 // platform to Java time zone ID mapping.
669 if (zoneID == null || zoneID.isEmpty()) {
670 String javaHome = StaticProperty.javaHome();
671 try {
672 zoneID = getSystemTimeZoneID(javaHome);
673 if (zoneID == null) {
674 zoneID = GMT_ID;
675 }
676 } catch (NullPointerException e) {
677 zoneID = GMT_ID;
678 }
679 }
680
681 // Get the time zone for zoneID. But not fall back to
682 // "GMT" here.
683 tz = getTimeZone(zoneID, false);
684
685 if (tz == null) {
686 // If the given zone ID is unknown in Java, try to
687 // get the GMT-offset-based time zone ID,
688 // a.k.a. custom time zone ID (e.g., "GMT-08:00").
689 String gmtOffsetID = getSystemGMTOffsetID();
690 if (gmtOffsetID != null) {
691 zoneID = gmtOffsetID;
692 }
693 tz = getTimeZone(zoneID, true);
694 }
695 assert tz != null;
696
697 final String id = zoneID;
698 props.setProperty("user.timezone", id);
699
700 defaultTimeZone = tz;
701 return tz;
702 }
703
704 /**
705 * Sets the {@code TimeZone} that is returned by the {@code getDefault}
706 * method. {@code zone} is cached. If {@code zone} is null, the cached
707 * default {@code TimeZone} is cleared. This method doesn't change the value
708 * of the {@code user.timezone} property.
709 *
710 * @param zone the new default {@code TimeZone}, or null
711 * @throws SecurityException if the security manager's {@code checkPermission}
712 * denies {@code PropertyPermission("user.timezone",
713 * "write")}
714 * @see #getDefault
715 * @see PropertyPermission
716 */
717 public static void setDefault(TimeZone zone)
718 {
719 SecurityManager sm = System.getSecurityManager();
720 if (sm != null) {
721 sm.checkPermission(new PropertyPermission
722 ("user.timezone", "write"));
723 }
724 // by saving a defensive clone and returning a clone in getDefault() too,
725 // the defaultTimeZone instance is isolated from user code which makes it
726 // effectively immutable. This is important to avoid races when the
727 // following is evaluated in ZoneId.systemDefault():
728 // TimeZone.getDefault().toZoneId().
729 defaultTimeZone = (zone == null) ? null : (TimeZone) zone.clone();
730 }
731
732 /**
733 * Returns true if this zone has the same rule and offset as another zone.
734 * That is, if this zone differs only in ID, if at all. Returns false
735 * if the other zone is null.
736 * @param other the <code>TimeZone</code> object to be compared with
737 * @return true if the other zone is not null and is the same as this one,
738 * with the possible exception of the ID
739 * @since 1.2
740 */
741 public boolean hasSameRules(TimeZone other) {
742 return other != null && getRawOffset() == other.getRawOffset() &&
743 useDaylightTime() == other.useDaylightTime();
744 }
745
746 /**
747 * Creates a copy of this <code>TimeZone</code>.
748 *
749 * @return a clone of this <code>TimeZone</code>
750 */
751 public Object clone()
752 {
753 try {
754 return super.clone();
755 } catch (CloneNotSupportedException e) {
756 throw new InternalError(e);
757 }
758 }
759
760 /**
761 * The null constant as a TimeZone.
762 */
763 static final TimeZone NO_TIMEZONE = null;
764
765 // =======================privates===============================
766
767 /**
768 * The string identifier of this <code>TimeZone</code>. This is a
769 * programmatic identifier used internally to look up <code>TimeZone</code>
770 * objects from the system table and also to map them to their localized
771 * display names. <code>ID</code> values are unique in the system
772 * table but may not be for dynamically created zones.
773 * @serial
774 */
775 private String ID;
776
777 /**
778 * Cached {@link ZoneId} for this TimeZone
779 */
780 private transient ZoneId zoneId;
781
782 private static volatile TimeZone defaultTimeZone;
783
784 static final String GMT_ID = "GMT";
785 private static final int GMT_ID_LENGTH = 3;
786
787 /**
788 * Parses a custom time zone identifier and returns a corresponding zone.
789 * This method doesn't support the RFC 822 time zone format. (e.g., +hhmm)
790 *
791 * @param id a string of the <a href="#CustomID">custom ID form</a>.
792 * @return a newly created TimeZone with the given offset and
793 * no daylight saving time, or null if the id cannot be parsed.
794 */
795 private static final TimeZone parseCustomTimeZone(String id) {
796 int length;
797
798 // Error if the length of id isn't long enough or id doesn't
799 // start with "GMT".
800 if ((length = id.length()) < (GMT_ID_LENGTH + 2) ||
801 id.indexOf(GMT_ID) != 0) {
802 return null;
803 }
804
805 ZoneInfo zi;
806
807 // First, we try to find it in the cache with the given
808 // id. Even the id is not normalized, the returned ZoneInfo
809 // should have its normalized id.
810 zi = ZoneInfoFile.getZoneInfo(id);
811 if (zi != null) {
812 return zi;
813 }
814
815 int index = GMT_ID_LENGTH;
816 boolean negative = false;
817 char c = id.charAt(index++);
818 if (c == '-') {
819 negative = true;
820 } else if (c != '+') {
821 return null;
822 }
823
824 int hours = 0;
825 int num = 0;
826 int countDelim = 0;
827 int len = 0;
828 while (index < length) {
829 c = id.charAt(index++);
830 if (c == ':') {
831 if (countDelim > 0) {
832 return null;
833 }
834 if (len > 2) {
835 return null;
836 }
837 hours = num;
838 countDelim++;
839 num = 0;
840 len = 0;
841 continue;
842 }
843 if (c < '0' || c > '9') {
844 return null;
845 }
846 num = num * 10 + (c - '0');
847 len++;
848 }
849 if (index != length) {
850 return null;
851 }
852 if (countDelim == 0) {
853 if (len <= 2) {
854 hours = num;
855 num = 0;
856 } else {
857 hours = num / 100;
858 num %= 100;
859 }
860 } else {
861 if (len != 2) {
862 return null;
863 }
864 }
865 if (hours > 23 || num > 59) {
866 return null;
867 }
868 int gmtOffset = (hours * 60 + num) * 60 * 1000;
869
870 if (gmtOffset == 0) {
871 zi = ZoneInfoFile.getZoneInfo(GMT_ID);
872 if (negative) {
873 zi.setID("GMT-00:00");
874 } else {
875 zi.setID("GMT+00:00");
876 }
877 } else {
878 zi = ZoneInfoFile.getCustomTimeZone(id, negative ? -gmtOffset : gmtOffset);
879 }
880 return zi;
881 }
882 }