1 /*
2 * Copyright (c) 2012, 2013, 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
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7 * published by the Free Software Foundation. Oracle designates this
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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).
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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) 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,
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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.chrono;
63
64 import java.time.Clock;
65 import java.time.DateTimeException;
66 import java.time.Instant;
67 import java.time.LocalDate;
68 import java.time.LocalTime;
69 import java.time.ZoneId;
70 import java.time.format.DateTimeFormatterBuilder;
71 import java.time.format.ResolverStyle;
72 import java.time.format.TextStyle;
73 import java.time.temporal.ChronoField;
74 import java.time.temporal.TemporalAccessor;
75 import java.time.temporal.TemporalField;
76 import java.time.temporal.TemporalQueries;
77 import java.time.temporal.TemporalQuery;
78 import java.time.temporal.UnsupportedTemporalTypeException;
79 import java.time.temporal.ValueRange;
80 import java.util.List;
81 import java.util.Locale;
82 import java.util.Map;
83 import java.util.Objects;
84 import java.util.Set;
85
86 /**
87 * A calendar system, used to organize and identify dates.
88 * <p>
89 * The main date and time API is built on the ISO calendar system.
90 * The chronology operates behind the scenes to represent the general concept of a calendar system.
91 * For example, the Japanese, Minguo, Thai Buddhist and others.
92 * <p>
93 * Most other calendar systems also operate on the shared concepts of year, month and day,
94 * linked to the cycles of the Earth around the Sun, and the Moon around the Earth.
95 * These shared concepts are defined by {@link ChronoField} and are available
96 * for use by any {@code Chronology} implementation:
97 * <pre>
98 * LocalDate isoDate = ...
99 * ThaiBuddhistDate thaiDate = ...
100 * int isoYear = isoDate.get(ChronoField.YEAR);
101 * int thaiYear = thaiDate.get(ChronoField.YEAR);
102 * </pre>
103 * As shown, although the date objects are in different calendar systems, represented by different
104 * {@code Chronology} instances, both can be queried using the same constant on {@code ChronoField}.
105 * For a full discussion of the implications of this, see {@link ChronoLocalDate}.
106 * In general, the advice is to use the known ISO-based {@code LocalDate}, rather than
107 * {@code ChronoLocalDate}.
108 * <p>
109 * While a {@code Chronology} object typically uses {@code ChronoField} and is based on
110 * an era, year-of-era, month-of-year, day-of-month model of a date, this is not required.
111 * A {@code Chronology} instance may represent a totally different kind of calendar system,
112 * such as the Mayan.
113 * <p>
114 * In practical terms, the {@code Chronology} instance also acts as a factory.
115 * The {@link #of(String)} method allows an instance to be looked up by identifier,
116 * while the {@link #ofLocale(Locale)} method allows lookup by locale.
117 * <p>
118 * The {@code Chronology} instance provides a set of methods to create {@code ChronoLocalDate} instances.
119 * The date classes are used to manipulate specific dates.
120 * <ul>
121 * <li> {@link #dateNow() dateNow()}
122 * <li> {@link #dateNow(Clock) dateNow(clock)}
123 * <li> {@link #dateNow(ZoneId) dateNow(zone)}
124 * <li> {@link #date(int, int, int) date(yearProleptic, month, day)}
125 * <li> {@link #date(Era, int, int, int) date(era, yearOfEra, month, day)}
126 * <li> {@link #dateYearDay(int, int) dateYearDay(yearProleptic, dayOfYear)}
127 * <li> {@link #dateYearDay(Era, int, int) dateYearDay(era, yearOfEra, dayOfYear)}
128 * <li> {@link #date(TemporalAccessor) date(TemporalAccessor)}
129 * </ul>
130 *
131 * <h3 id="addcalendars">Adding New Calendars</h3>
132 * The set of available chronologies can be extended by applications.
133 * Adding a new calendar system requires the writing of an implementation of
134 * {@code Chronology}, {@code ChronoLocalDate} and {@code Era}.
135 * The majority of the logic specific to the calendar system will be in the
136 * {@code ChronoLocalDate} implementation.
137 * The {@code Chronology} implementation acts as a factory.
138 * <p>
139 * To permit the discovery of additional chronologies, the {@link java.util.ServiceLoader ServiceLoader}
140 * is used. A file must be added to the {@code META-INF/services} directory with the
141 * name 'java.time.chrono.Chronology' listing the implementation classes.
142 * See the ServiceLoader for more details on service loading.
143 * For lookup by id or calendarType, the system provided calendars are found
144 * first followed by application provided calendars.
145 * <p>
146 * Each chronology must define a chronology ID that is unique within the system.
147 * If the chronology represents a calendar system defined by the
148 * CLDR specification then the calendar type is the concatenation of the
149 * CLDR type and, if applicable, the CLDR variant,
150 *
151 * @implSpec
152 * This interface must be implemented with care to ensure other classes operate correctly.
153 * All implementations that can be instantiated must be final, immutable and thread-safe.
154 * Subclasses should be Serializable wherever possible.
155 *
156 * @since 1.8
157 */
158 public interface Chronology extends Comparable<Chronology> {
159
160 /**
161 * Obtains an instance of {@code Chronology} from a temporal object.
162 * <p>
163 * This obtains a chronology based on the specified temporal.
164 * A {@code TemporalAccessor} represents an arbitrary set of date and time information,
165 * which this factory converts to an instance of {@code Chronology}.
166 * <p>
167 * The conversion will obtain the chronology using {@link TemporalQueries#chronology()}.
168 * If the specified temporal object does not have a chronology, {@link IsoChronology} is returned.
169 * <p>
170 * This method matches the signature of the functional interface {@link TemporalQuery}
171 * allowing it to be used as a query via method reference, {@code Chronology::from}.
172 *
173 * @param temporal the temporal to convert, not null
174 * @return the chronology, not null
175 * @throws DateTimeException if unable to convert to an {@code Chronology}
176 */
177 static Chronology from(TemporalAccessor temporal) {
178 Objects.requireNonNull(temporal, "temporal");
179 Chronology obj = temporal.query(TemporalQueries.chronology());
180 return Objects.requireNonNullElse(obj, IsoChronology.INSTANCE);
181 }
182
183 //-----------------------------------------------------------------------
184 /**
185 * Obtains an instance of {@code Chronology} from a locale.
186 * <p>
187 * This returns a {@code Chronology} based on the specified locale,
188 * typically returning {@code IsoChronology}. Other calendar systems
189 * are only returned if they are explicitly selected within the locale.
190 * <p>
191 * The {@link Locale} class provide access to a range of information useful
192 * for localizing an application. This includes the language and region,
193 * such as "en-GB" for English as used in Great Britain.
194 * <p>
195 * The {@code Locale} class also supports an extension mechanism that
196 * can be used to identify a calendar system. The mechanism is a form
197 * of key-value pairs, where the calendar system has the key "ca".
198 * For example, the locale "en-JP-u-ca-japanese" represents the English
199 * language as used in Japan with the Japanese calendar system.
200 * <p>
201 * This method finds the desired calendar system by in a manner equivalent
202 * to passing "ca" to {@link Locale#getUnicodeLocaleType(String)}.
203 * If the "ca" key is not present, then {@code IsoChronology} is returned.
204 * <p>
205 * Note that the behavior of this method differs from the older
206 * {@link java.util.Calendar#getInstance(Locale)} method.
207 * If that method receives a locale of "th_TH" it will return {@code BuddhistCalendar}.
208 * By contrast, this method will return {@code IsoChronology}.
209 * Passing the locale "th-TH-u-ca-buddhist" into either method will
210 * result in the Thai Buddhist calendar system and is therefore the
211 * recommended approach going forward for Thai calendar system localization.
212 * <p>
213 * A similar, but simpler, situation occurs for the Japanese calendar system.
214 * The locale "jp_JP_JP" has previously been used to access the calendar.
215 * However, unlike the Thai locale, "ja_JP_JP" is automatically converted by
216 * {@code Locale} to the modern and recommended form of "ja-JP-u-ca-japanese".
217 * Thus, there is no difference in behavior between this method and
218 * {@code Calendar#getInstance(Locale)}.
219 *
220 * @param locale the locale to use to obtain the calendar system, not null
221 * @return the calendar system associated with the locale, not null
222 * @throws DateTimeException if the locale-specified calendar cannot be found
223 */
224 static Chronology ofLocale(Locale locale) {
225 return AbstractChronology.ofLocale(locale);
226 }
227
228 //-----------------------------------------------------------------------
229 /**
230 * Obtains an instance of {@code Chronology} from a chronology ID or
231 * calendar system type.
232 * <p>
233 * This returns a chronology based on either the ID or the type.
234 * The {@link #getId() chronology ID} uniquely identifies the chronology.
235 * The {@link #getCalendarType() calendar system type} is defined by the
236 * CLDR specification.
237 * <p>
238 * The chronology may be a system chronology or a chronology
239 * provided by the application via ServiceLoader configuration.
240 * <p>
241 * Since some calendars can be customized, the ID or type typically refers
242 * to the default customization. For example, the Gregorian calendar can have multiple
243 * cutover dates from the Julian, but the lookup only provides the default cutover date.
244 *
245 * @param id the chronology ID or calendar system type, not null
246 * @return the chronology with the identifier requested, not null
247 * @throws DateTimeException if the chronology cannot be found
248 */
249 static Chronology of(String id) {
250 return AbstractChronology.of(id);
251 }
252
253 /**
254 * Returns the available chronologies.
255 * <p>
256 * Each returned {@code Chronology} is available for use in the system.
257 * The set of chronologies includes the system chronologies and
258 * any chronologies provided by the application via ServiceLoader
259 * configuration.
260 *
261 * @return the independent, modifiable set of the available chronology IDs, not null
262 */
263 static Set<Chronology> getAvailableChronologies() {
264 return AbstractChronology.getAvailableChronologies();
265 }
266
267 //-----------------------------------------------------------------------
268 /**
269 * Gets the ID of the chronology.
270 * <p>
271 * The ID uniquely identifies the {@code Chronology}.
272 * It can be used to lookup the {@code Chronology} using {@link #of(String)}.
273 *
274 * @return the chronology ID, not null
275 * @see #getCalendarType()
276 */
277 String getId();
278
279 /**
280 * Gets the calendar type of the calendar system.
281 * <p>
282 * The calendar type is an identifier defined by the CLDR and
283 * <em>Unicode Locale Data Markup Language (LDML)</em> specifications
284 * to uniquely identification a calendar.
285 * The {@code getCalendarType} is the concatenation of the CLDR calendar type
286 * and the variant, if applicable, is appended separated by "-".
287 * The calendar type is used to lookup the {@code Chronology} using {@link #of(String)}.
288 *
289 * @return the calendar system type, null if the calendar is not defined by CLDR/LDML
290 * @see #getId()
291 */
292 String getCalendarType();
293
294 //-----------------------------------------------------------------------
295 /**
296 * Obtains a local date in this chronology from the era, year-of-era,
297 * month-of-year and day-of-month fields.
298 *
299 * @implSpec
300 * The default implementation combines the era and year-of-era into a proleptic
301 * year before calling {@link #date(int, int, int)}.
302 *
303 * @param era the era of the correct type for the chronology, not null
304 * @param yearOfEra the chronology year-of-era
305 * @param month the chronology month-of-year
306 * @param dayOfMonth the chronology day-of-month
307 * @return the local date in this chronology, not null
308 * @throws DateTimeException if unable to create the date
309 * @throws ClassCastException if the {@code era} is not of the correct type for the chronology
310 */
311 default ChronoLocalDate date(Era era, int yearOfEra, int month, int dayOfMonth) {
312 return date(prolepticYear(era, yearOfEra), month, dayOfMonth);
313 }
314
315 /**
316 * Obtains a local date in this chronology from the proleptic-year,
317 * month-of-year and day-of-month fields.
318 *
319 * @param prolepticYear the chronology proleptic-year
320 * @param month the chronology month-of-year
321 * @param dayOfMonth the chronology day-of-month
322 * @return the local date in this chronology, not null
323 * @throws DateTimeException if unable to create the date
324 */
325 ChronoLocalDate date(int prolepticYear, int month, int dayOfMonth);
326
327 /**
328 * Obtains a local date in this chronology from the era, year-of-era and
329 * day-of-year fields.
330 *
331 * @implSpec
332 * The default implementation combines the era and year-of-era into a proleptic
333 * year before calling {@link #dateYearDay(int, int)}.
334 *
335 * @param era the era of the correct type for the chronology, not null
336 * @param yearOfEra the chronology year-of-era
337 * @param dayOfYear the chronology day-of-year
338 * @return the local date in this chronology, not null
339 * @throws DateTimeException if unable to create the date
340 * @throws ClassCastException if the {@code era} is not of the correct type for the chronology
341 */
342 default ChronoLocalDate dateYearDay(Era era, int yearOfEra, int dayOfYear) {
343 return dateYearDay(prolepticYear(era, yearOfEra), dayOfYear);
344 }
345
346 /**
347 * Obtains a local date in this chronology from the proleptic-year and
348 * day-of-year fields.
349 *
350 * @param prolepticYear the chronology proleptic-year
351 * @param dayOfYear the chronology day-of-year
352 * @return the local date in this chronology, not null
353 * @throws DateTimeException if unable to create the date
354 */
355 ChronoLocalDate dateYearDay(int prolepticYear, int dayOfYear);
356
357 /**
358 * Obtains a local date in this chronology from the epoch-day.
359 * <p>
360 * The definition of {@link ChronoField#EPOCH_DAY EPOCH_DAY} is the same
361 * for all calendar systems, thus it can be used for conversion.
362 *
363 * @param epochDay the epoch day
364 * @return the local date in this chronology, not null
365 * @throws DateTimeException if unable to create the date
366 */
367 ChronoLocalDate dateEpochDay(long epochDay);
368
369 //-----------------------------------------------------------------------
370 /**
371 * Obtains the current local date in this chronology from the system clock in the default time-zone.
372 * <p>
373 * This will query the {@link Clock#systemDefaultZone() system clock} in the default
374 * time-zone to obtain the current date.
375 * <p>
376 * Using this method will prevent the ability to use an alternate clock for testing
377 * because the clock is hard-coded.
378 *
379 * @implSpec
380 * The default implementation invokes {@link #dateNow(Clock)}.
381 *
382 * @return the current local date using the system clock and default time-zone, not null
383 * @throws DateTimeException if unable to create the date
384 */
385 default ChronoLocalDate dateNow() {
386 return dateNow(Clock.systemDefaultZone());
387 }
388
389 /**
390 * Obtains the current local date in this chronology from the system clock in the specified time-zone.
391 * <p>
392 * This will query the {@link Clock#system(ZoneId) system clock} to obtain the current date.
393 * Specifying the time-zone avoids dependence on the default time-zone.
394 * <p>
395 * Using this method will prevent the ability to use an alternate clock for testing
396 * because the clock is hard-coded.
397 *
398 * @implSpec
399 * The default implementation invokes {@link #dateNow(Clock)}.
400 *
401 * @param zone the zone ID to use, not null
402 * @return the current local date using the system clock, not null
403 * @throws DateTimeException if unable to create the date
404 */
405 default ChronoLocalDate dateNow(ZoneId zone) {
406 return dateNow(Clock.system(zone));
407 }
408
409 /**
410 * Obtains the current local date in this chronology from the specified clock.
411 * <p>
412 * This will query the specified clock to obtain the current date - today.
413 * Using this method allows the use of an alternate clock for testing.
414 * The alternate clock may be introduced using {@link Clock dependency injection}.
415 *
416 * @implSpec
417 * The default implementation invokes {@link #date(TemporalAccessor)}.
418 *
419 * @param clock the clock to use, not null
420 * @return the current local date, not null
421 * @throws DateTimeException if unable to create the date
422 */
423 default ChronoLocalDate dateNow(Clock clock) {
424 Objects.requireNonNull(clock, "clock");
425 return date(LocalDate.now(clock));
426 }
427
428 //-----------------------------------------------------------------------
429 /**
430 * Obtains a local date in this chronology from another temporal object.
431 * <p>
432 * This obtains a date in this chronology based on the specified temporal.
433 * A {@code TemporalAccessor} represents an arbitrary set of date and time information,
434 * which this factory converts to an instance of {@code ChronoLocalDate}.
435 * <p>
436 * The conversion typically uses the {@link ChronoField#EPOCH_DAY EPOCH_DAY}
437 * field, which is standardized across calendar systems.
438 * <p>
439 * This method matches the signature of the functional interface {@link TemporalQuery}
440 * allowing it to be used as a query via method reference, {@code aChronology::date}.
441 *
442 * @param temporal the temporal object to convert, not null
443 * @return the local date in this chronology, not null
444 * @throws DateTimeException if unable to create the date
445 * @see ChronoLocalDate#from(TemporalAccessor)
446 */
447 ChronoLocalDate date(TemporalAccessor temporal);
448
449 /**
450 * Obtains a local date-time in this chronology from another temporal object.
451 * <p>
452 * This obtains a date-time in this chronology based on the specified temporal.
453 * A {@code TemporalAccessor} represents an arbitrary set of date and time information,
454 * which this factory converts to an instance of {@code ChronoLocalDateTime}.
455 * <p>
456 * The conversion extracts and combines the {@code ChronoLocalDate} and the
457 * {@code LocalTime} from the temporal object.
458 * Implementations are permitted to perform optimizations such as accessing
459 * those fields that are equivalent to the relevant objects.
460 * The result uses this chronology.
461 * <p>
462 * This method matches the signature of the functional interface {@link TemporalQuery}
463 * allowing it to be used as a query via method reference, {@code aChronology::localDateTime}.
464 *
465 * @param temporal the temporal object to convert, not null
466 * @return the local date-time in this chronology, not null
467 * @throws DateTimeException if unable to create the date-time
468 * @see ChronoLocalDateTime#from(TemporalAccessor)
469 */
470 default ChronoLocalDateTime<? extends ChronoLocalDate> localDateTime(TemporalAccessor temporal) {
471 try {
472 return date(temporal).atTime(LocalTime.from(temporal));
473 } catch (DateTimeException ex) {
474 throw new DateTimeException("Unable to obtain ChronoLocalDateTime from TemporalAccessor: " + temporal.getClass(), ex);
475 }
476 }
477
478 /**
479 * Obtains a {@code ChronoZonedDateTime} in this chronology from another temporal object.
480 * <p>
481 * This obtains a zoned date-time in this chronology based on the specified temporal.
482 * A {@code TemporalAccessor} represents an arbitrary set of date and time information,
483 * which this factory converts to an instance of {@code ChronoZonedDateTime}.
484 * <p>
485 * The conversion will first obtain a {@code ZoneId} from the temporal object,
486 * falling back to a {@code ZoneOffset} if necessary. It will then try to obtain
487 * an {@code Instant}, falling back to a {@code ChronoLocalDateTime} if necessary.
488 * The result will be either the combination of {@code ZoneId} or {@code ZoneOffset}
489 * with {@code Instant} or {@code ChronoLocalDateTime}.
490 * Implementations are permitted to perform optimizations such as accessing
491 * those fields that are equivalent to the relevant objects.
492 * The result uses this chronology.
493 * <p>
494 * This method matches the signature of the functional interface {@link TemporalQuery}
495 * allowing it to be used as a query via method reference, {@code aChronology::zonedDateTime}.
496 *
497 * @param temporal the temporal object to convert, not null
498 * @return the zoned date-time in this chronology, not null
499 * @throws DateTimeException if unable to create the date-time
500 * @see ChronoZonedDateTime#from(TemporalAccessor)
501 */
502 default ChronoZonedDateTime<? extends ChronoLocalDate> zonedDateTime(TemporalAccessor temporal) {
503 try {
504 ZoneId zone = ZoneId.from(temporal);
505 try {
506 Instant instant = Instant.from(temporal);
507 return zonedDateTime(instant, zone);
508
509 } catch (DateTimeException ex1) {
510 ChronoLocalDateTimeImpl<?> cldt = ChronoLocalDateTimeImpl.ensureValid(this, localDateTime(temporal));
511 return ChronoZonedDateTimeImpl.ofBest(cldt, zone, null);
512 }
513 } catch (DateTimeException ex) {
514 throw new DateTimeException("Unable to obtain ChronoZonedDateTime from TemporalAccessor: " + temporal.getClass(), ex);
515 }
516 }
517
518 /**
519 * Obtains a {@code ChronoZonedDateTime} in this chronology from an {@code Instant}.
520 * <p>
521 * This obtains a zoned date-time with the same instant as that specified.
522 *
523 * @param instant the instant to create the date-time from, not null
524 * @param zone the time-zone, not null
525 * @return the zoned date-time, not null
526 * @throws DateTimeException if the result exceeds the supported range
527 */
528 default ChronoZonedDateTime<? extends ChronoLocalDate> zonedDateTime(Instant instant, ZoneId zone) {
529 return ChronoZonedDateTimeImpl.ofInstant(this, instant, zone);
530 }
531
532 //-----------------------------------------------------------------------
533 /**
534 * Checks if the specified year is a leap year.
535 * <p>
536 * A leap-year is a year of a longer length than normal.
537 * The exact meaning is determined by the chronology according to the following constraints.
538 * <ul>
539 * <li>a leap-year must imply a year-length longer than a non leap-year.
540 * <li>a chronology that does not support the concept of a year must return false.
541 * <li>the correct result must be returned for all years within the
542 * valid range of years for the chronology.
543 * </ul>
544 * <p>
545 * Outside the range of valid years an implementation is free to return
546 * either a best guess or false.
547 * An implementation must not throw an exception, even if the year is
548 * outside the range of valid years.
549 *
550 * @param prolepticYear the proleptic-year to check, not validated for range
551 * @return true if the year is a leap year
552 */
553 boolean isLeapYear(long prolepticYear);
554
555 /**
556 * Calculates the proleptic-year given the era and year-of-era.
557 * <p>
558 * This combines the era and year-of-era into the single proleptic-year field.
559 * <p>
560 * If the chronology makes active use of eras, such as {@code JapaneseChronology}
561 * then the year-of-era will be validated against the era.
562 * For other chronologies, validation is optional.
563 *
564 * @param era the era of the correct type for the chronology, not null
565 * @param yearOfEra the chronology year-of-era
566 * @return the proleptic-year
567 * @throws DateTimeException if unable to convert to a proleptic-year,
568 * such as if the year is invalid for the era
569 * @throws ClassCastException if the {@code era} is not of the correct type for the chronology
570 */
571 int prolepticYear(Era era, int yearOfEra);
572
573 /**
574 * Creates the chronology era object from the numeric value.
575 * <p>
576 * The era is, conceptually, the largest division of the time-line.
577 * Most calendar systems have a single epoch dividing the time-line into two eras.
578 * However, some have multiple eras, such as one for the reign of each leader.
579 * The exact meaning is determined by the chronology according to the following constraints.
580 * <p>
581 * The era in use at 1970-01-01 must have the value 1.
582 * Later eras must have sequentially higher values.
583 * Earlier eras must have sequentially lower values.
584 * Each chronology must refer to an enum or similar singleton to provide the era values.
585 * <p>
586 * This method returns the singleton era of the correct type for the specified era value.
587 *
588 * @param eraValue the era value
589 * @return the calendar system era, not null
590 * @throws DateTimeException if unable to create the era
591 */
592 Era eraOf(int eraValue);
593
594 /**
595 * Gets the list of eras for the chronology.
596 * <p>
597 * Most calendar systems have an era, within which the year has meaning.
598 * If the calendar system does not support the concept of eras, an empty
599 * list must be returned.
600 *
601 * @return the list of eras for the chronology, may be immutable, not null
602 */
603 List<Era> eras();
604
605 //-----------------------------------------------------------------------
606 /**
607 * Gets the range of valid values for the specified field.
608 * <p>
609 * All fields can be expressed as a {@code long} integer.
610 * This method returns an object that describes the valid range for that value.
611 * <p>
612 * Note that the result only describes the minimum and maximum valid values
613 * and it is important not to read too much into them. For example, there
614 * could be values within the range that are invalid for the field.
615 * <p>
616 * This method will return a result whether or not the chronology supports the field.
617 *
618 * @param field the field to get the range for, not null
619 * @return the range of valid values for the field, not null
620 * @throws DateTimeException if the range for the field cannot be obtained
621 */
622 ValueRange range(ChronoField field);
623
624 //-----------------------------------------------------------------------
625 /**
626 * Gets the textual representation of this chronology.
627 * <p>
628 * This returns the textual name used to identify the chronology,
629 * suitable for presentation to the user.
630 * The parameters control the style of the returned text and the locale.
631 *
632 * @implSpec
633 * The default implementation behaves as though the formatter was used to
634 * format the chronology textual name.
635 *
636 * @param style the style of the text required, not null
637 * @param locale the locale to use, not null
638 * @return the text value of the chronology, not null
639 */
640 default String getDisplayName(TextStyle style, Locale locale) {
641 TemporalAccessor temporal = new TemporalAccessor() {
642 @Override
643 public boolean isSupported(TemporalField field) {
644 return false;
645 }
646 @Override
647 public long getLong(TemporalField field) {
648 throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
649 }
650 @SuppressWarnings("unchecked")
651 @Override
652 public <R> R query(TemporalQuery<R> query) {
653 if (query == TemporalQueries.chronology()) {
654 return (R) Chronology.this;
655 }
656 return TemporalAccessor.super.query(query);
657 }
658 };
659 return new DateTimeFormatterBuilder().appendChronologyText(style).toFormatter(locale).format(temporal);
660 }
661
662 //-----------------------------------------------------------------------
663 /**
664 * Resolves parsed {@code ChronoField} values into a date during parsing.
665 * <p>
666 * Most {@code TemporalField} implementations are resolved using the
667 * resolve method on the field. By contrast, the {@code ChronoField} class
668 * defines fields that only have meaning relative to the chronology.
669 * As such, {@code ChronoField} date fields are resolved here in the
670 * context of a specific chronology.
671 * <p>
672 * The default implementation, which explains typical resolve behaviour,
673 * is provided in {@link AbstractChronology}.
674 *
675 * @param fieldValues the map of fields to values, which can be updated, not null
676 * @param resolverStyle the requested type of resolve, not null
677 * @return the resolved date, null if insufficient information to create a date
678 * @throws DateTimeException if the date cannot be resolved, typically
679 * because of a conflict in the input data
680 */
681 ChronoLocalDate resolveDate(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle);
682
683 //-----------------------------------------------------------------------
684 /**
685 * Obtains a period for this chronology based on years, months and days.
686 * <p>
687 * This returns a period tied to this chronology using the specified
688 * years, months and days. All supplied chronologies use periods
689 * based on years, months and days, however the {@code ChronoPeriod} API
690 * allows the period to be represented using other units.
691 *
692 * @implSpec
693 * The default implementation returns an implementation class suitable
694 * for most calendar systems. It is based solely on the three units.
695 * Normalization, addition and subtraction derive the number of months
696 * in a year from the {@link #range(ChronoField)}. If the number of
697 * months within a year is fixed, then the calculation approach for
698 * addition, subtraction and normalization is slightly different.
699 * <p>
700 * If implementing an unusual calendar system that is not based on
701 * years, months and days, or where you want direct control, then
702 * the {@code ChronoPeriod} interface must be directly implemented.
703 * <p>
704 * The returned period is immutable and thread-safe.
705 *
706 * @param years the number of years, may be negative
707 * @param months the number of years, may be negative
708 * @param days the number of years, may be negative
709 * @return the period in terms of this chronology, not null
710 */
711 default ChronoPeriod period(int years, int months, int days) {
712 return new ChronoPeriodImpl(this, years, months, days);
713 }
714
715 //-----------------------------------------------------------------------
716 /**
717 * Compares this chronology to another chronology.
718 * <p>
719 * The comparison order first by the chronology ID string, then by any
720 * additional information specific to the subclass.
721 * It is "consistent with equals", as defined by {@link Comparable}.
722 *
723 * @param other the other chronology to compare to, not null
724 * @return the comparator value, negative if less, positive if greater
725 */
726 @Override
727 int compareTo(Chronology other);
728
729 /**
730 * Checks if this chronology is equal to another chronology.
731 * <p>
732 * The comparison is based on the entire state of the object.
733 *
734 * @param obj the object to check, null returns false
735 * @return true if this is equal to the other chronology
736 */
737 @Override
738 boolean equals(Object obj);
739
740 /**
741 * A hash code for this chronology.
742 * <p>
743 * The hash code should be based on the entire state of the object.
744 *
745 * @return a suitable hash code
746 */
747 @Override
748 int hashCode();
749
750 //-----------------------------------------------------------------------
751 /**
752 * Outputs this chronology as a {@code String}.
753 * <p>
754 * The format should include the entire state of the object.
755 *
756 * @return a string representation of this chronology, not null
757 */
758 @Override
759 String toString();
760
761 }