1 /*
2 * Copyright (c) 2012, 2024, 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 * This file is available under and governed by the GNU General Public
28 * License version 2 only, as published by the Free Software Foundation.
29 * However, the following notice accompanied the original version of this
30 * file:
31 *
32 * Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos
33 *
34 * All rights reserved.
35 *
36 * Redistribution and use in source and binary forms, with or without
37 * modification, are permitted provided that the following conditions are met:
38 *
39 * * Redistributions of source code must retain the above copyright notice,
40 * this list of conditions and the following disclaimer.
41 *
42 * * Redistributions in binary form must reproduce the above copyright notice,
43 * this list of conditions and the following disclaimer in the documentation
44 * and/or other materials provided with the distribution.
45 *
46 * * Neither the name of JSR-310 nor the names of its contributors
47 * may be used to endorse or promote products derived from this software
48 * without specific prior written permission.
49 *
50 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
51 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
52 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
53 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
54 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
55 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
56 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
57 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
58 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
59 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
60 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
61 */
62 package java.time;
63
64 import java.io.DataOutput;
65 import java.io.IOException;
66 import java.io.InvalidObjectException;
67 import java.io.ObjectInputStream;
68 import java.io.Serializable;
69 import java.time.format.DateTimeFormatterBuilder;
70 import java.time.format.TextStyle;
71 import java.time.temporal.TemporalAccessor;
72 import java.time.temporal.TemporalField;
73 import java.time.temporal.TemporalQueries;
74 import java.time.temporal.TemporalQuery;
75 import java.time.temporal.UnsupportedTemporalTypeException;
76 import java.time.zone.ZoneRules;
77 import java.time.zone.ZoneRulesException;
78 import java.time.zone.ZoneRulesProvider;
79 import java.util.HashSet;
80 import java.util.Locale;
81 import java.util.Map;
82 import java.util.Objects;
83 import java.util.Set;
84 import java.util.TimeZone;
85
86 import static java.util.Map.entry;
87
88 /**
89 * A time-zone ID, such as {@code Europe/Paris}.
90 * <p>
91 * A {@code ZoneId} is used to identify the rules used to convert between
92 * an {@link Instant} and a {@link LocalDateTime}.
93 * There are two distinct types of ID:
94 * <ul>
95 * <li>Fixed offsets - a fully resolved offset from UTC/Greenwich, that uses
96 * the same offset for all local date-times
97 * <li>Geographical regions - an area where a specific set of rules for finding
98 * the offset from UTC/Greenwich apply
99 * </ul>
100 * Most fixed offsets are represented by {@link ZoneOffset}.
101 * Calling {@link #normalized()} on any {@code ZoneId} will ensure that a
102 * fixed offset ID will be represented as a {@code ZoneOffset}.
103 * <p>
104 * The actual rules, describing when and how the offset changes, are defined by {@link ZoneRules}.
105 * This class is simply an ID used to obtain the underlying rules.
106 * This approach is taken because rules are defined by governments and change
107 * frequently, whereas the ID is stable.
108 * <p>
109 * The distinction has other effects. Serializing the {@code ZoneId} will only send
110 * the ID, whereas serializing the rules sends the entire data set.
111 * Similarly, a comparison of two IDs only examines the ID, whereas
112 * a comparison of two rules examines the entire data set.
113 *
114 * <h2>Time-zone IDs</h2>
115 * The ID is unique within the system.
116 * There are three types of ID.
117 * <p>
118 * The simplest type of ID is that from {@code ZoneOffset}.
119 * This consists of 'Z' and IDs starting with '+' or '-'.
120 * <p>
121 * The next type of ID are offset-style IDs with some form of prefix,
122 * such as 'GMT+2' or 'UTC+01:00'.
123 * The recognised prefixes are 'UTC', 'GMT' and 'UT'.
124 * The offset is the suffix and will be normalized during creation.
125 * These IDs can be normalized to a {@code ZoneOffset} using {@code normalized()}.
126 * <p>
127 * The third type of ID are region-based IDs. A region-based ID must be of
128 * two or more characters, and not start with 'UTC', 'GMT', 'UT' '+' or '-'.
129 * Region-based IDs are defined by configuration, see {@link ZoneRulesProvider}.
130 * The configuration focuses on providing the lookup from the ID to the
131 * underlying {@code ZoneRules}.
132 * <p>
133 * Time-zone rules are defined by governments and change frequently.
134 * There are a number of organizations, known here as groups, that monitor
135 * time-zone changes and collate them.
136 * The default group is the IANA Time Zone Database (TZDB).
137 * Other organizations include IATA (the airline industry body) and Microsoft.
138 * <p>
139 * Each group defines its own format for the region ID it provides.
140 * The TZDB group defines IDs such as 'Europe/London' or 'America/New_York'.
141 * TZDB IDs take precedence over other groups.
142 * <p>
143 * It is strongly recommended that the group name is included in all IDs supplied by
144 * groups other than TZDB to avoid conflicts. For example, IATA airline time-zone
145 * region IDs are typically the same as the three letter airport code.
146 * However, the airport of Utrecht has the code 'UTC', which is obviously a conflict.
147 * The recommended format for region IDs from groups other than TZDB is 'group~region'.
148 * Thus if IATA data were defined, Utrecht airport would be 'IATA~UTC'.
149 *
150 * <h2>Serialization</h2>
151 * This class can be serialized and stores the string zone ID in the external form.
152 * The {@code ZoneOffset} subclass uses a dedicated format that only stores the
153 * offset from UTC/Greenwich.
154 * <p>
155 * A {@code ZoneId} can be deserialized in a Java Runtime where the ID is unknown.
156 * For example, if a server-side Java Runtime has been updated with a new zone ID, but
157 * the client-side Java Runtime has not been updated. In this case, the {@code ZoneId}
158 * object will exist, and can be queried using {@code getId}, {@code equals},
159 * {@code hashCode}, {@code toString}, {@code getDisplayName} and {@code normalized}.
160 * However, any call to {@code getRules} will fail with {@code ZoneRulesException}.
161 * This approach is designed to allow a {@link ZonedDateTime} to be loaded and
162 * queried, but not modified, on a Java Runtime with incomplete time-zone information.
163 * <p>
164 * This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
165 * class; programmers should treat instances that are
166 * {@linkplain #equals(Object) equal} as interchangeable and should not
167 * use instances for synchronization, or unpredictable behavior may
168 * occur. For example, in a future release, synchronization may fail.
169 * The {@code equals} method should be used for comparisons.
170 *
171 * @implSpec
172 * This abstract sealed class permits two implementations, both of which are immutable and
173 * thread-safe. One implementation models region-based IDs, the other is {@code ZoneOffset}
174 * modelling offset-based IDs. This difference is visible in serialization.
175 *
176 * @since 1.8
177 * @sealedGraph
178 */
179 @jdk.internal.ValueBased
180 public abstract sealed class ZoneId implements Serializable permits ZoneOffset, ZoneRegion {
181
182 /**
183 * A map of zone overrides to enable the short time-zone names to be used.
184 * <p>
185 * Use of short zone IDs has been deprecated in {@code java.util.TimeZone}.
186 * This map allows the IDs to continue to be used via the
187 * {@link #of(String, Map)} factory method.
188 * <p>
189 * This map contains a mapping of the IDs that is in line with TZDB 2024b and
190 * later, where 'EST', 'MST' and 'HST' map to IDs which do not include daylight
191 * savings since 1970. This mapping may change in update releases in support of new versions of TZDB.
192 * <p>
193 * This maps as follows:
194 * <ul>
195 * <li>ACT - Australia/Darwin</li>
196 * <li>AET - Australia/Sydney</li>
197 * <li>AGT - America/Argentina/Buenos_Aires</li>
198 * <li>ART - Africa/Cairo</li>
199 * <li>AST - America/Anchorage</li>
200 * <li>BET - America/Sao_Paulo</li>
201 * <li>BST - Asia/Dhaka</li>
202 * <li>CAT - Africa/Harare</li>
203 * <li>CNT - America/St_Johns</li>
204 * <li>CST - America/Chicago</li>
205 * <li>CTT - Asia/Shanghai</li>
206 * <li>EAT - Africa/Addis_Ababa</li>
207 * <li>ECT - Europe/Paris</li>
208 * <li>EST - America/Panama</li>
209 * <li>HST - Pacific/Honolulu</li>
210 * <li>IET - America/Indiana/Indianapolis</li>
211 * <li>IST - Asia/Kolkata</li>
212 * <li>JST - Asia/Tokyo</li>
213 * <li>MIT - Pacific/Apia</li>
214 * <li>MST - America/Phoenix</li>
215 * <li>NET - Asia/Yerevan</li>
216 * <li>NST - Pacific/Auckland</li>
217 * <li>PLT - Asia/Karachi</li>
218 * <li>PNT - America/Phoenix</li>
219 * <li>PRT - America/Puerto_Rico</li>
220 * <li>PST - America/Los_Angeles</li>
221 * <li>SST - Pacific/Guadalcanal</li>
222 * <li>VST - Asia/Ho_Chi_Minh</li>
223 * </ul>
224 * The map is unmodifiable.
225 */
226 public static final Map<String, String> SHORT_IDS = Map.ofEntries(
227 entry("ACT", "Australia/Darwin"),
228 entry("AET", "Australia/Sydney"),
229 entry("AGT", "America/Argentina/Buenos_Aires"),
230 entry("ART", "Africa/Cairo"),
231 entry("AST", "America/Anchorage"),
232 entry("BET", "America/Sao_Paulo"),
233 entry("BST", "Asia/Dhaka"),
234 entry("CAT", "Africa/Harare"),
235 entry("CNT", "America/St_Johns"),
236 entry("CST", "America/Chicago"),
237 entry("CTT", "Asia/Shanghai"),
238 entry("EAT", "Africa/Addis_Ababa"),
239 entry("ECT", "Europe/Paris"),
240 entry("IET", "America/Indiana/Indianapolis"),
241 entry("IST", "Asia/Kolkata"),
242 entry("JST", "Asia/Tokyo"),
243 entry("MIT", "Pacific/Apia"),
244 entry("NET", "Asia/Yerevan"),
245 entry("NST", "Pacific/Auckland"),
246 entry("PLT", "Asia/Karachi"),
247 entry("PNT", "America/Phoenix"),
248 entry("PRT", "America/Puerto_Rico"),
249 entry("PST", "America/Los_Angeles"),
250 entry("SST", "Pacific/Guadalcanal"),
251 entry("VST", "Asia/Ho_Chi_Minh"),
252 entry("EST", "America/Panama"),
253 entry("MST", "America/Phoenix"),
254 entry("HST", "Pacific/Honolulu")
255 );
256 /**
257 * Serialization version.
258 */
259 @java.io.Serial
260 private static final long serialVersionUID = 8352817235686L;
261
262 //-----------------------------------------------------------------------
263 /**
264 * Gets the system default time-zone.
265 * <p>
266 * This queries {@link TimeZone#getDefault()} to find the default time-zone
267 * and converts it to a {@code ZoneId}. If the system default time-zone is changed,
268 * then the result of this method will also change.
269 *
270 * @return the zone ID, not null
271 * @throws DateTimeException if the converted zone ID has an invalid format
272 * @throws ZoneRulesException if the converted zone region ID cannot be found
273 */
274 public static ZoneId systemDefault() {
275 return TimeZone.getDefault().toZoneId();
276 }
277
278 /**
279 * Gets the set of available zone IDs.
280 * <p>
281 * This set includes the string form of all available region-based IDs.
282 * Offset-based zone IDs are not included in the returned set.
283 * The ID can be passed to {@link #of(String)} to create a {@code ZoneId}.
284 * <p>
285 * The set of zone IDs can increase over time, although in a typical application
286 * the set of IDs is fixed. Each call to this method is thread-safe.
287 *
288 * @return a modifiable copy of the set of zone IDs, not null
289 */
290 public static Set<String> getAvailableZoneIds() {
291 return new HashSet<String>(ZoneRulesProvider.getAvailableZoneIds());
292 }
293
294 //-----------------------------------------------------------------------
295 /**
296 * Obtains an instance of {@code ZoneId} using its ID using a map
297 * of aliases to supplement the standard zone IDs.
298 * <p>
299 * Many users of time-zones use short abbreviations, such as PST for
300 * 'Pacific Standard Time' and PDT for 'Pacific Daylight Time'.
301 * These abbreviations are not unique, and so cannot be used as IDs.
302 * This method allows a map of string to time-zone to be setup and reused
303 * within an application.
304 *
305 * @param zoneId the time-zone ID, not null
306 * @param aliasMap a map of alias zone IDs (typically abbreviations) to real zone IDs, not null
307 * @return the zone ID, not null
308 * @throws DateTimeException if the zone ID has an invalid format
309 * @throws ZoneRulesException if the zone ID is a region ID that cannot be found
310 */
311 public static ZoneId of(String zoneId, Map<String, String> aliasMap) {
312 Objects.requireNonNull(zoneId, "zoneId");
313 Objects.requireNonNull(aliasMap, "aliasMap");
314 String id = Objects.requireNonNullElse(aliasMap.get(zoneId), zoneId);
315 return of(id);
316 }
317
318 /**
319 * Obtains an instance of {@code ZoneId} from an ID ensuring that the
320 * ID is valid and available for use.
321 * <p>
322 * This method parses the ID producing a {@code ZoneId} or {@code ZoneOffset}.
323 * A {@code ZoneOffset} is returned if the ID is 'Z', or starts with '+' or '-'.
324 * The result will always be a valid ID for which {@link ZoneRules} can be obtained.
325 * <p>
326 * Parsing matches the zone ID step by step as follows.
327 * <ul>
328 * <li>If the zone ID equals 'Z', the result is {@code ZoneOffset.UTC}.
329 * <li>If the zone ID consists of a single letter, the zone ID is invalid
330 * and {@code DateTimeException} is thrown.
331 * <li>If the zone ID starts with '+' or '-', the ID is parsed as a
332 * {@code ZoneOffset} using {@link ZoneOffset#of(String)}.
333 * <li>If the zone ID equals 'GMT', 'UTC' or 'UT' then the result is a {@code ZoneId}
334 * with the same ID and rules equivalent to {@code ZoneOffset.UTC}.
335 * <li>If the zone ID starts with 'UTC+', 'UTC-', 'GMT+', 'GMT-', 'UT+' or 'UT-'
336 * then the ID is a prefixed offset-based ID. The ID is split in two, with
337 * a two or three letter prefix and a suffix starting with the sign.
338 * The suffix is parsed as a {@link ZoneOffset#of(String) ZoneOffset}.
339 * The result will be a {@code ZoneId} with the specified UTC/GMT/UT prefix
340 * and the normalized offset ID as per {@link ZoneOffset#getId()}.
341 * The rules of the returned {@code ZoneId} will be equivalent to the
342 * parsed {@code ZoneOffset}.
343 * <li>All other IDs are parsed as region-based zone IDs. Region IDs must
344 * match the regular expression {@code [A-Za-z][A-Za-z0-9~/._+-]+}
345 * otherwise a {@code DateTimeException} is thrown. If the zone ID is not
346 * in the configured set of IDs, {@code ZoneRulesException} is thrown.
347 * The detailed format of the region ID depends on the group supplying the data.
348 * The default set of data is supplied by the IANA Time Zone Database (TZDB).
349 * This has region IDs of the form '{area}/{city}', such as 'Europe/Paris' or 'America/New_York'.
350 * This is compatible with most IDs from {@link java.util.TimeZone}.
351 * </ul>
352 *
353 * @param zoneId the time-zone ID, not null
354 * @return the zone ID, not null
355 * @throws DateTimeException if the zone ID has an invalid format
356 * @throws ZoneRulesException if the zone ID is a region ID that cannot be found
357 */
358 public static ZoneId of(String zoneId) {
359 return of(zoneId, true);
360 }
361
362 /**
363 * Obtains an instance of {@code ZoneId} wrapping an offset.
364 * <p>
365 * If the prefix is "GMT", "UTC", or "UT" a {@code ZoneId}
366 * with the prefix and the non-zero offset is returned.
367 * If the prefix is empty {@code ""} the {@code ZoneOffset} is returned.
368 *
369 * @param prefix the time-zone ID, not null
370 * @param offset the offset, not null
371 * @return the zone ID, not null
372 * @throws IllegalArgumentException if the prefix is not one of
373 * "GMT", "UTC", or "UT", or ""
374 */
375 public static ZoneId ofOffset(String prefix, ZoneOffset offset) {
376 Objects.requireNonNull(prefix, "prefix");
377 Objects.requireNonNull(offset, "offset");
378 if (prefix.isEmpty()) {
379 return offset;
380 }
381
382 if (!prefix.equals("GMT") && !prefix.equals("UTC") && !prefix.equals("UT")) {
383 throw new IllegalArgumentException("prefix should be GMT, UTC or UT, is: " + prefix);
384 }
385
386 if (offset.getTotalSeconds() != 0) {
387 prefix = prefix.concat(offset.getId());
388 }
389 return new ZoneRegion(prefix, offset.getRules());
390 }
391
392 /**
393 * Parses the ID, taking a flag to indicate whether {@code ZoneRulesException}
394 * should be thrown or not, used in deserialization.
395 *
396 * @param zoneId the time-zone ID, not null
397 * @param checkAvailable whether to check if the zone ID is available
398 * @return the zone ID, not null
399 * @throws DateTimeException if the ID format is invalid
400 * @throws ZoneRulesException if checking availability and the ID cannot be found
401 */
402 static ZoneId of(String zoneId, boolean checkAvailable) {
403 Objects.requireNonNull(zoneId, "zoneId");
404 if (zoneId.length() <= 1 || zoneId.startsWith("+") || zoneId.startsWith("-")) {
405 return ZoneOffset.of(zoneId);
406 } else if (zoneId.startsWith("UTC") || zoneId.startsWith("GMT")) {
407 return ofWithPrefix(zoneId, 3, checkAvailable);
408 } else if (zoneId.startsWith("UT")) {
409 return ofWithPrefix(zoneId, 2, checkAvailable);
410 }
411 return ZoneRegion.ofId(zoneId, checkAvailable);
412 }
413
414 /**
415 * Parse once a prefix is established.
416 *
417 * @param zoneId the time-zone ID, not null
418 * @param prefixLength the length of the prefix, 2 or 3
419 * @return the zone ID, not null
420 * @throws DateTimeException if the zone ID has an invalid format
421 */
422 private static ZoneId ofWithPrefix(String zoneId, int prefixLength, boolean checkAvailable) {
423 String prefix = zoneId.substring(0, prefixLength);
424 if (zoneId.length() == prefixLength) {
425 return ofOffset(prefix, ZoneOffset.UTC);
426 }
427 if (zoneId.charAt(prefixLength) != '+' && zoneId.charAt(prefixLength) != '-') {
428 return ZoneRegion.ofId(zoneId, checkAvailable); // drop through to ZoneRulesProvider
429 }
430 try {
431 ZoneOffset offset = ZoneOffset.of(zoneId.substring(prefixLength));
432 if (offset == ZoneOffset.UTC) {
433 return ofOffset(prefix, offset);
434 }
435 return ofOffset(prefix, offset);
436 } catch (DateTimeException ex) {
437 throw new DateTimeException("Invalid ID for offset-based ZoneId: " + zoneId, ex);
438 }
439 }
440
441 //-----------------------------------------------------------------------
442 /**
443 * Obtains an instance of {@code ZoneId} from a temporal object.
444 * <p>
445 * This obtains a zone based on the specified temporal.
446 * A {@code TemporalAccessor} represents an arbitrary set of date and time information,
447 * which this factory converts to an instance of {@code ZoneId}.
448 * <p>
449 * A {@code TemporalAccessor} represents some form of date and time information.
450 * This factory converts the arbitrary temporal object to an instance of {@code ZoneId}.
451 * <p>
452 * The conversion will try to obtain the zone in a way that favours region-based
453 * zones over offset-based zones using {@link TemporalQueries#zone()}.
454 * <p>
455 * This method matches the signature of the functional interface {@link TemporalQuery}
456 * allowing it to be used as a query via method reference, {@code ZoneId::from}.
457 *
458 * @param temporal the temporal object to convert, not null
459 * @return the zone ID, not null
460 * @throws DateTimeException if unable to convert to a {@code ZoneId}
461 */
462 public static ZoneId from(TemporalAccessor temporal) {
463 ZoneId obj = temporal.query(TemporalQueries.zone());
464 if (obj == null) {
465 throw new DateTimeException("Unable to obtain ZoneId from TemporalAccessor: " +
466 temporal + " of type " + temporal.getClass().getName());
467 }
468 return obj;
469 }
470
471 //-----------------------------------------------------------------------
472 /**
473 * Constructor only accessible within the package.
474 */
475 ZoneId() {}
476
477 //-----------------------------------------------------------------------
478 /**
479 * Gets the unique time-zone ID.
480 * <p>
481 * This ID uniquely defines this object.
482 * The format of an offset based ID is defined by {@link ZoneOffset#getId()}.
483 *
484 * @return the time-zone unique ID, not null
485 */
486 public abstract String getId();
487
488 //-----------------------------------------------------------------------
489 /**
490 * Gets the textual representation of the zone, such as 'British Time' or
491 * '+02:00'.
492 * <p>
493 * This returns the textual name used to identify the time-zone ID,
494 * suitable for presentation to the user.
495 * The parameters control the style of the returned text and the locale.
496 * <p>
497 * If no textual mapping is found then the {@link #getId() full ID} is returned.
498 *
499 * @param style the length of the text required, not null
500 * @param locale the locale to use, not null
501 * @return the text value of the zone, not null
502 */
503 public String getDisplayName(TextStyle style, Locale locale) {
504 return new DateTimeFormatterBuilder().appendZoneText(style).toFormatter(locale).format(toTemporal());
505 }
506
507 /**
508 * Converts this zone to a {@code TemporalAccessor}.
509 * <p>
510 * A {@code ZoneId} can be fully represented as a {@code TemporalAccessor}.
511 * However, the interface is not implemented by this class as most of the
512 * methods on the interface have no meaning to {@code ZoneId}.
513 * <p>
514 * The returned temporal has no supported fields, with the query method
515 * supporting the return of the zone using {@link TemporalQueries#zoneId()}.
516 *
517 * @return a temporal equivalent to this zone, not null
518 */
519 private TemporalAccessor toTemporal() {
520 return new TemporalAccessor() {
521 @Override
522 public boolean isSupported(TemporalField field) {
523 return false;
524 }
525 @Override
526 public long getLong(TemporalField field) {
527 throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
528 }
529 @SuppressWarnings("unchecked")
530 @Override
531 public <R> R query(TemporalQuery<R> query) {
532 if (query == TemporalQueries.zoneId()) {
533 return (R) ZoneId.this;
534 }
535 return TemporalAccessor.super.query(query);
536 }
537 };
538 }
539
540 //-----------------------------------------------------------------------
541 /**
542 * Gets the time-zone rules for this ID allowing calculations to be performed.
543 * <p>
544 * The rules provide the functionality associated with a time-zone,
545 * such as finding the offset for a given instant or local date-time.
546 * <p>
547 * A time-zone can be invalid if it is deserialized in a Java Runtime which
548 * does not have the same rules loaded as the Java Runtime that stored it.
549 * In this case, calling this method will throw a {@code ZoneRulesException}.
550 * <p>
551 * The rules are supplied by {@link ZoneRulesProvider}. An advanced provider may
552 * support dynamic updates to the rules without restarting the Java Runtime.
553 * If so, then the result of this method may change over time.
554 * Each individual call will be still remain thread-safe.
555 * <p>
556 * {@link ZoneOffset} will always return a set of rules where the offset never changes.
557 *
558 * @return the rules, not null
559 * @throws ZoneRulesException if no rules are available for this ID
560 */
561 public abstract ZoneRules getRules();
562
563 /**
564 * Normalizes the time-zone ID, returning a {@code ZoneOffset} where possible.
565 * <p>
566 * The returns a normalized {@code ZoneId} that can be used in place of this ID.
567 * The result will have {@code ZoneRules} equivalent to those returned by this object,
568 * however the ID returned by {@code getId()} may be different.
569 * <p>
570 * The normalization checks if the rules of this {@code ZoneId} have a fixed offset.
571 * If they do, then the {@code ZoneOffset} equal to that offset is returned.
572 * Otherwise {@code this} is returned.
573 *
574 * @return the time-zone unique ID, not null
575 */
576 public ZoneId normalized() {
577 try {
578 ZoneRules rules = getRules();
579 if (rules.isFixedOffset()) {
580 return rules.getOffset(Instant.EPOCH);
581 }
582 } catch (ZoneRulesException ex) {
583 // invalid ZoneRegion is not important to this method
584 }
585 return this;
586 }
587
588 /**
589 * Get the effective offset for an instant at the given epochSecond.
590 */
591 /* package-private */ abstract ZoneOffset getOffset(long epochSecond);
592
593 //-----------------------------------------------------------------------
594 /**
595 * Checks if this time-zone ID is equal to another time-zone ID.
596 * <p>
597 * The comparison is based on the ID.
598 *
599 * @param obj the object to check, null returns false
600 * @return true if this is equal to the other time-zone ID
601 */
602 @Override
603 public boolean equals(Object obj) {
604 if (this == obj) {
605 return true;
606 }
607 return (obj instanceof ZoneId other)
608 && getId().equals(other.getId());
609 }
610
611 /**
612 * A hash code for this time-zone ID.
613 *
614 * @return a suitable hash code
615 */
616 @Override
617 public int hashCode() {
618 return getId().hashCode();
619 }
620
621 //-----------------------------------------------------------------------
622 /**
623 * Defend against malicious streams.
624 *
625 * @param s the stream to read
626 * @throws InvalidObjectException always
627 */
628 @java.io.Serial
629 private void readObject(ObjectInputStream s) throws InvalidObjectException {
630 throw new InvalidObjectException("Deserialization via serialization delegate");
631 }
632
633 /**
634 * Outputs this zone as a {@code String}, using the ID.
635 *
636 * @return a string representation of this time-zone ID, not null
637 */
638 @Override
639 public String toString() {
640 return getId();
641 }
642
643 //-----------------------------------------------------------------------
644 /**
645 * Writes the object using a
646 * <a href="{@docRoot}/serialized-form.html#java.time.Ser">dedicated serialized form</a>.
647 * @serialData
648 * <pre>
649 * out.writeByte(7); // identifies a ZoneId (not ZoneOffset)
650 * out.writeUTF(getId());
651 * </pre>
652 * <p>
653 * When read back in, the {@code ZoneId} will be created as though using
654 * {@link #of(String)}, but without any exception in the case where the
655 * ID has a valid format, but is not in the known set of region-based IDs.
656 *
657 * @return the instance of {@code Ser}, not null
658 */
659 // this is here for serialization Javadoc
660 @java.io.Serial
661 private Object writeReplace() {
662 return new Ser(Ser.ZONE_REGION_TYPE, this);
663 }
664
665 abstract void write(DataOutput out) throws IOException;
666
667 }