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
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
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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,
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.chrono;
63
64 import static java.time.temporal.ChronoField.EPOCH_DAY;
65 import static java.time.temporal.ChronoField.ERA;
66 import static java.time.temporal.ChronoField.YEAR;
67 import static java.time.temporal.ChronoUnit.DAYS;
68
69 import java.time.DateTimeException;
70 import java.time.LocalDate;
71 import java.time.LocalTime;
72 import java.time.Period;
73 import java.time.format.DateTimeFormatter;
74 import java.time.temporal.ChronoField;
75 import java.time.temporal.ChronoUnit;
76 import java.time.temporal.Queries;
77 import java.time.temporal.Temporal;
78 import java.time.temporal.TemporalAccessor;
79 import java.time.temporal.TemporalAdjuster;
80 import java.time.temporal.TemporalAmount;
81 import java.time.temporal.TemporalField;
82 import java.time.temporal.TemporalQuery;
83 import java.time.temporal.TemporalUnit;
84 import java.util.Comparator;
85 import java.util.Objects;
86
87 /**
88 * A date without time-of-day or time-zone in an arbitrary chronology, intended
89 * for advanced globalization use cases.
90 * <p>
91 * <b>Most applications should declare method signatures, fields and variables
92 * as {@link LocalDate}, not this interface.</b>
93 * <p>
94 * A {@code ChronoLocalDate} is the abstract representation of a date where the
95 * {@code Chronology chronology}, or calendar system, is pluggable.
96 * The date is defined in terms of fields expressed by {@link TemporalField},
97 * where most common implementations are defined in {@link ChronoField}.
98 * The chronology defines how the calendar system operates and the meaning of
99 * the standard fields.
100 *
101 * <h3>When to use this interface</h3>
102 * The design of the API encourages the use of {@code LocalDate} rather than this
103 * interface, even in the case where the application needs to deal with multiple
104 * calendar systems. The rationale for this is explored in the following documentation.
105 * <p>
106 * The primary use case where this interface should be used is where the generic
107 * type parameter {@code <D>} is fully defined as a specific chronology.
108 * In that case, the assumptions of that chronology are known at development
109 * time and specified in the code.
110 * <p>
111 * When the chronology is defined in the generic type parameter as ? or otherwise
112 * unknown at development time, the rest of the discussion below applies.
113 * <p>
114 * To emphasize the point, declaring a method signature, field or variable as this
115 * interface type can initially seem like the sensible way to globalize an application,
116 * however it is usually the wrong approach.
117 * As such, it should be considered an application-wide architectural decision to choose
118 * to use this interface as opposed to {@code LocalDate}.
119 *
120 * <h3>Architectural issues to consider</h3>
121 * These are some of the points that must be considered before using this interface
122 * throughout an application.
123 * <p>
124 * 1) Applications using this interface, as opposed to using just {@code LocalDate},
125 * face a significantly higher probability of bugs. This is because the calendar system
126 * in use is not known at development time. A key cause of bugs is where the developer
127 * applies assumptions from their day-to-day knowledge of the ISO calendar system
128 * to code that is intended to deal with any arbitrary calendar system.
129 * The section below outlines how those assumptions can cause problems
130 * The primary mechanism for reducing this increased risk of bugs is a strong code review process.
131 * This should also be considered a extra cost in maintenance for the lifetime of the code.
132 * <p>
133 * 2) This interface does not enforce immutability of implementations.
134 * While the implementation notes indicate that all implementations must be immutable
135 * there is nothing in the code or type system to enforce this. Any method declared
136 * to accept a {@code ChronoLocalDate} could therefore be passed a poorly or
137 * maliciously written mutable implementation.
138 * <p>
139 * 3) Applications using this interface must consider the impact of eras.
140 * {@code LocalDate} shields users from the concept of eras, by ensuring that {@code getYear()}
141 * returns the proleptic year. That decision ensures that developers can think of
142 * {@code LocalDate} instances as consisting of three fields - year, month-of-year and day-of-month.
143 * By contrast, users of this interface must think of dates as consisting of four fields -
144 * era, year-of-era, month-of-year and day-of-month. The extra era field is frequently
145 * forgotten, yet it is of vital importance to dates in an arbitrary calendar system.
146 * For example, in the Japanese calendar system, the era represents the reign of an Emperor.
147 * Whenever one reign ends and another starts, the year-of-era is reset to one.
148 * <p>
149 * 4) The only agreed international standard for passing a date between two systems
150 * is the ISO-8601 standard which requires the ISO calendar system. Using this interface
151 * throughout the application will inevitably lead to the requirement to pass the date
152 * across a network or component boundary, requiring an application specific protocol or format.
153 * <p>
154 * 5) Long term persistence, such as a database, will almost always only accept dates in the
155 * ISO-8601 calendar system (or the related Julian-Gregorian). Passing around dates in other
156 * calendar systems increases the complications of interacting with persistence.
157 * <p>
158 * 6) Most of the time, passing a {@code ChronoLocalDate} throughout an application
159 * is unnecessary, as discussed in the last section below.
160 *
161 * <h3>False assumptions causing bugs in multi-calendar system code</h3>
162 * As indicated above, there are many issues to consider when try to use and manipulate a
163 * date in an arbitrary calendar system. These are some of the key issues.
164 * <p>
165 * Code that queries the day-of-month and assumes that the value will never be more than
166 * 31 is invalid. Some calendar systems have more than 31 days in some months.
167 * <p>
168 * Code that adds 12 months to a date and assumes that a year has been added is invalid.
169 * Some calendar systems have a different number of months, such as 13 in the Coptic or Ethiopic.
170 * <p>
171 * Code that adds one month to a date and assumes that the month-of-year value will increase
172 * by one or wrap to the next year is invalid. Some calendar systems have a variable number
173 * of months in a year, such as the Hebrew.
174 * <p>
175 * Code that adds one month, then adds a second one month and assumes that the day-of-month
176 * will remain close to its original value is invalid. Some calendar systems have a large difference
177 * between the length of the longest month and the length of the shortest month.
178 * For example, the Coptic or Ethiopic have 12 months of 30 days and 1 month of 5 days.
179 * <p>
180 * Code that adds seven days and assumes that a week has been added is invalid.
181 * Some calendar systems have weeks of other than seven days, such as the French Revolutionary.
182 * <p>
183 * Code that assumes that because the year of {@code date1} is greater than the year of {@code date2}
184 * then {@code date1} is after {@code date2} is invalid. This is invalid for all calendar systems
185 * when referring to the year-of-era, and especially untrue of the Japanese calendar system
186 * where the year-of-era restarts with the reign of every new Emperor.
187 * <p>
188 * Code that treats month-of-year one and day-of-month one as the start of the year is invalid.
189 * Not all calendar systems start the year when the month value is one.
190 * <p>
191 * In general, manipulating a date, and even querying a date, is wide open to bugs when the
192 * calendar system is unknown at development time. This is why it is essential that code using
193 * this interface is subjected to additional code reviews. It is also why an architectural
194 * decision to avoid this interface type is usually the correct one.
195 *
196 * <h3>Using LocalDate instead</h3>
197 * The primary alternative to using this interface throughout your application is as follows.
198 * <p><ul>
199 * <li>Declare all method signatures referring to dates in terms of {@code LocalDate}.
200 * <li>Either store the chronology (calendar system) in the user profile or lookup
201 * the chronology from the user locale
202 * <li>Convert the ISO {@code LocalDate} to and from the user's preferred calendar system during
203 * printing and parsing
204 * </ul><p>
205 * This approach treats the problem of globalized calendar systems as a localization issue
206 * and confines it to the UI layer. This approach is in keeping with other localization
207 * issues in the java platform.
208 * <p>
209 * As discussed above, performing calculations on a date where the rules of the calendar system
210 * are pluggable requires skill and is not recommended.
211 * Fortunately, the need to perform calculations on a date in an arbitrary calendar system
212 * is extremely rare. For example, it is highly unlikely that the business rules of a library
213 * book rental scheme will allow rentals to be for one month, where meaning of the month
214 * is dependent on the user's preferred calendar system.
215 * <p>
216 * A key use case for calculations on a date in an arbitrary calendar system is producing
217 * a month-by-month calendar for display and user interaction. Again, this is a UI issue,
218 * and use of this interface solely within a few methods of the UI layer may be justified.
219 * <p>
220 * In any other part of the system, where a date must be manipulated in a calendar system
221 * other than ISO, the use case will generally specify the calendar system to use.
222 * For example, an application may need to calculate the next Islamic or Hebrew holiday
223 * which may require manipulating the date.
224 * This kind of use case can be handled as follows:
225 * <p><ul>
226 * <li>start from the ISO {@code LocalDate} being passed to the method
227 * <li>convert the date to the alternate calendar system, which for this use case is known
228 * rather than arbitrary
229 * <li>perform the calculation
230 * <li>convert back to {@code LocalDate}
231 * </ul><p>
232 * Developers writing low-level frameworks or libraries should also avoid this interface.
233 * Instead, one of the two general purpose access interfaces should be used.
234 * Use {@link TemporalAccessor} if read-only access is required, or use {@link Temporal}
235 * if read-write access is required.
236 *
237 * <h3>Specification for implementors</h3>
238 * This interface must be implemented with care to ensure other classes operate correctly.
239 * All implementations that can be instantiated must be final, immutable and thread-safe.
240 * Subclasses should be Serializable wherever possible.
241 * <p>
242 * Additional calendar systems may be added to the system.
243 * See {@link Chronology} for more details.
244 *
245 * @param <D> the concrete type for the date
246 * @since 1.8
247 */
248 public interface ChronoLocalDate<D extends ChronoLocalDate<D>>
249 extends Temporal, TemporalAdjuster, Comparable<ChronoLocalDate<?>> {
250
251 /**
252 * Comparator for two {@code ChronoLocalDate}s ignoring the chronology.
253 * <p>
254 * This comparator differs from the comparison in {@link #compareTo} in that it
255 * only compares the underlying date and not the chronology.
256 * This allows dates in different calendar systems to be compared based
257 * on the time-line position.
258 * This is equivalent to using {@code Long.compare(date1.toEpochDay(), date2.toEpochDay())}.
259 *
260 * @see #isAfter
261 * @see #isBefore
262 * @see #isEqual
263 */
264 public static final Comparator<ChronoLocalDate<?>> DATE_COMPARATOR =
265 new Comparator<ChronoLocalDate<?>>() {
266 @Override
267 public int compare(ChronoLocalDate<?> date1, ChronoLocalDate<?> date2) {
268 return Long.compare(date1.toEpochDay(), date2.toEpochDay());
269 }
270 };
271
272 //-----------------------------------------------------------------------
273 /**
274 * Gets the chronology of this date.
275 * <p>
276 * The {@code Chronology} represents the calendar system in use.
277 * The era and other fields in {@link ChronoField} are defined by the chronology.
278 *
279 * @return the chronology, not null
280 */
281 Chronology getChronology();
282
283 /**
284 * Gets the era, as defined by the chronology.
285 * <p>
286 * The era is, conceptually, the largest division of the time-line.
287 * Most calendar systems have a single epoch dividing the time-line into two eras.
288 * However, some have multiple eras, such as one for the reign of each leader.
289 * The exact meaning is determined by the {@code Chronology}.
290 * <p>
291 * All correctly implemented {@code Era} classes are singletons, thus it
292 * is valid code to write {@code date.getEra() == SomeChrono.ERA_NAME)}.
293 * <p>
294 * This default implementation uses {@link Chronology#eraOf(int)}.
295 *
296 * @return the chronology specific era constant applicable at this date, not null
297 */
298 public default Era getEra() {
299 return getChronology().eraOf(get(ERA));
300 }
301
302 /**
303 * Checks if the year is a leap year, as defined by the calendar system.
304 * <p>
305 * A leap-year is a year of a longer length than normal.
306 * The exact meaning is determined by the chronology with the constraint that
307 * a leap-year must imply a year-length longer than a non leap-year.
308 * <p>
309 * This default implementation uses {@link Chronology#isLeapYear(long)}.
310 *
311 * @return true if this date is in a leap year, false otherwise
312 */
313 public default boolean isLeapYear() {
314 return getChronology().isLeapYear(getLong(YEAR));
315 }
316
317 /**
318 * Returns the length of the month represented by this date, as defined by the calendar system.
319 * <p>
320 * This returns the length of the month in days.
321 *
322 * @return the length of the month in days
323 */
324 int lengthOfMonth();
325
326 /**
327 * Returns the length of the year represented by this date, as defined by the calendar system.
328 * <p>
329 * This returns the length of the year in days.
330 * <p>
331 * The default implementation uses {@link #isLeapYear()} and returns 365 or 366.
332 *
333 * @return the length of the year in days
334 */
335 public default int lengthOfYear() {
336 return (isLeapYear() ? 366 : 365);
337 }
338
339 @Override
340 public default boolean isSupported(TemporalField field) {
341 if (field instanceof ChronoField) {
342 return ((ChronoField) field).isDateField();
343 }
344 return field != null && field.isSupportedBy(this);
345 }
346
347 //-----------------------------------------------------------------------
348 // override for covariant return type
349 /**
350 * {@inheritDoc}
351 * @throws DateTimeException {@inheritDoc}
352 * @throws ArithmeticException {@inheritDoc}
353 */
354 @Override
355 public default D with(TemporalAdjuster adjuster) {
356 return (D) getChronology().ensureChronoLocalDate(Temporal.super.with(adjuster));
357 }
358
359 /**
360 * {@inheritDoc}
361 * @throws DateTimeException {@inheritDoc}
362 * @throws ArithmeticException {@inheritDoc}
363 */
364 @Override
365 public default D with(TemporalField field, long newValue) {
366 if (field instanceof ChronoField) {
367 throw new DateTimeException("Unsupported field: " + field.getName());
368 }
369 return (D) getChronology().ensureChronoLocalDate(field.adjustInto(this, newValue));
370 }
371
372 /**
373 * {@inheritDoc}
374 * @throws DateTimeException {@inheritDoc}
375 * @throws ArithmeticException {@inheritDoc}
376 */
377 @Override
378 public default D plus(TemporalAmount amount) {
379 return (D) getChronology().ensureChronoLocalDate(Temporal.super.plus(amount));
380 }
381
382 /**
383 * {@inheritDoc}
384 * @throws DateTimeException {@inheritDoc}
385 * @throws ArithmeticException {@inheritDoc}
386 */
387 @Override
388 public default D plus(long amountToAdd, TemporalUnit unit) {
389 if (unit instanceof ChronoUnit) {
390 throw new DateTimeException("Unsupported unit: " + unit.getName());
391 }
392 return (D) getChronology().ensureChronoLocalDate(unit.addTo(this, amountToAdd));
393 }
394
395 /**
396 * {@inheritDoc}
397 * @throws DateTimeException {@inheritDoc}
398 * @throws ArithmeticException {@inheritDoc}
399 */
400 @Override
401 public default D minus(TemporalAmount amount) {
402 return (D) getChronology().ensureChronoLocalDate(Temporal.super.minus(amount));
403 }
404
405 /**
406 * {@inheritDoc}
407 * @throws DateTimeException {@inheritDoc}
408 * @throws ArithmeticException {@inheritDoc}
409 */
410 @Override
411 public default D minus(long amountToSubtract, TemporalUnit unit) {
412 return (D) getChronology().ensureChronoLocalDate(Temporal.super.minus(amountToSubtract, unit));
413 }
414
415 //-----------------------------------------------------------------------
416 /**
417 * Queries this date using the specified query.
418 * <p>
419 * This queries this date using the specified query strategy object.
420 * The {@code TemporalQuery} object defines the logic to be used to
421 * obtain the result. Read the documentation of the query to understand
422 * what the result of this method will be.
423 * <p>
424 * The result of this method is obtained by invoking the
425 * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
426 * specified query passing {@code this} as the argument.
427 *
428 * @param <R> the type of the result
429 * @param query the query to invoke, not null
430 * @return the query result, null may be returned (defined by the query)
431 * @throws DateTimeException if unable to query (defined by the query)
432 * @throws ArithmeticException if numeric overflow occurs (defined by the query)
433 */
434 @SuppressWarnings("unchecked")
435 @Override
436 public default <R> R query(TemporalQuery<R> query) {
437 if (query == Queries.zoneId() || query == Queries.zone() || query == Queries.offset()) {
438 return null;
439 } else if (query == Queries.localTime()) {
440 return null;
441 } else if (query == Queries.chronology()) {
442 return (R) getChronology();
443 } else if (query == Queries.precision()) {
444 return (R) DAYS;
445 }
446 // inline TemporalAccessor.super.query(query) as an optimization
447 // non-JDK classes are not permitted to make this optimization
448 return query.queryFrom(this);
449 }
450
451 /**
452 * Adjusts the specified temporal object to have the same date as this object.
453 * <p>
454 * This returns a temporal object of the same observable type as the input
455 * with the date changed to be the same as this.
456 * <p>
457 * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
458 * passing {@link ChronoField#EPOCH_DAY} as the field.
459 * <p>
460 * In most cases, it is clearer to reverse the calling pattern by using
461 * {@link Temporal#with(TemporalAdjuster)}:
462 * <pre>
463 * // these two lines are equivalent, but the second approach is recommended
464 * temporal = thisLocalDate.adjustInto(temporal);
465 * temporal = temporal.with(thisLocalDate);
466 * </pre>
467 * <p>
468 * This instance is immutable and unaffected by this method call.
469 *
470 * @param temporal the target object to be adjusted, not null
471 * @return the adjusted object, not null
472 * @throws DateTimeException if unable to make the adjustment
473 * @throws ArithmeticException if numeric overflow occurs
474 */
475 @Override
476 public default Temporal adjustInto(Temporal temporal) {
477 return temporal.with(EPOCH_DAY, toEpochDay());
478 }
479
480 /**
481 * Calculates the period between this date and another date in
482 * terms of the specified unit.
483 * <p>
484 * This calculates the period between two dates in terms of a single unit.
485 * The start and end points are {@code this} and the specified date.
486 * The result will be negative if the end is before the start.
487 * The {@code Temporal} passed to this method must be a
488 * {@code ChronoLocalDate} in the same chronology.
489 * The calculation returns a whole number, representing the number of
490 * complete units between the two dates.
491 * For example, the period in days between two dates can be calculated
492 * using {@code startDate.periodUntil(endDate, DAYS)}.
493 * <p>
494 * There are two equivalent ways of using this method.
495 * The first is to invoke this method.
496 * The second is to use {@link TemporalUnit#between(Temporal, Temporal)}:
497 * <pre>
498 * // these two lines are equivalent
499 * amount = start.periodUntil(end, MONTHS);
500 * amount = MONTHS.between(start, end);
501 * </pre>
502 * The choice should be made based on which makes the code more readable.
503 * <p>
504 * The calculation is implemented in this method for {@link ChronoUnit}.
505 * The units {@code DAYS}, {@code WEEKS}, {@code MONTHS}, {@code YEARS},
506 * {@code DECADES}, {@code CENTURIES}, {@code MILLENNIA} and {@code ERAS}
507 * should be supported by all implementations.
508 * Other {@code ChronoUnit} values will throw an exception.
509 * <p>
510 * If the unit is not a {@code ChronoUnit}, then the result of this method
511 * is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)}
512 * passing {@code this} as the first argument and the input temporal as
513 * the second argument.
514 * <p>
515 * This instance is immutable and unaffected by this method call.
516 *
517 * @param endDate the end date, which must be a {@code ChronoLocalDate}
518 * in the same chronology, not null
519 * @param unit the unit to measure the period in, not null
520 * @return the amount of the period between this date and the end date
521 * @throws DateTimeException if the period cannot be calculated
522 * @throws ArithmeticException if numeric overflow occurs
523 */
524 @Override // override for Javadoc
525 public abstract long periodUntil(Temporal endDate, TemporalUnit unit);
526
527 /**
528 * Calculates the period between this date and another date as a {@code Period}.
529 * <p>
530 * This calculates the period between two dates in terms of years, months and days.
531 * The start and end points are {@code this} and the specified date.
532 * The result will be negative if the end is before the start.
533 * <p>
534 * The calculation is performed using the the chronology of this date.
535 * If necessary, the input date will be converted to match.
536 * <p>
537 * The result of this method can be a negative period if the end is before the start.
538 * The negative sign will be the same in each of year, month and day.
539 * <p>
540 * This instance is immutable and unaffected by this method call.
541 *
542 * @param endDate the end date, exclusive, which may be in any chronology, not null
543 * @return the period between this date and the end date, not null
544 * @throws DateTimeException if the period cannot be calculated
545 * @throws ArithmeticException if numeric overflow occurs
546 */
547 public abstract Period periodUntil(ChronoLocalDate<?> endDate);
548
549 //-----------------------------------------------------------------------
550 /**
551 * Combines this date with a time to create a {@code ChronoLocalDateTime}.
552 * <p>
553 * This returns a {@code ChronoLocalDateTime} formed from this date at the specified time.
554 * All possible combinations of date and time are valid.
555 *
556 * @param localTime the local time to use, not null
557 * @return the local date-time formed from this date and the specified time, not null
558 */
559 public default ChronoLocalDateTime<D> atTime(LocalTime localTime) {
560 return (ChronoLocalDateTime<D>)ChronoLocalDateTimeImpl.of(this, localTime);
561 }
562
563 //-----------------------------------------------------------------------
564 /**
565 * Converts this date to the Epoch Day.
566 * <p>
567 * The {@link ChronoField#EPOCH_DAY Epoch Day count} is a simple
568 * incrementing count of days where day 0 is 1970-01-01 (ISO).
569 * This definition is the same for all chronologies, enabling conversion.
570 * <p>
571 * This default implementation queries the {@code EPOCH_DAY} field.
572 *
573 * @return the Epoch Day equivalent to this date
574 */
575 public default long toEpochDay() {
576 return getLong(EPOCH_DAY);
577 }
578
579 //-----------------------------------------------------------------------
580 /**
581 * Compares this date to another date, including the chronology.
582 * <p>
583 * The comparison is based first on the underlying time-line date, then
584 * on the chronology.
585 * It is "consistent with equals", as defined by {@link Comparable}.
586 * <p>
587 * For example, the following is the comparator order:
588 * <ol>
589 * <li>{@code 2012-12-03 (ISO)}</li>
590 * <li>{@code 2012-12-04 (ISO)}</li>
591 * <li>{@code 2555-12-04 (ThaiBuddhist)}</li>
592 * <li>{@code 2012-12-05 (ISO)}</li>
593 * </ol>
594 * Values #2 and #3 represent the same date on the time-line.
595 * When two values represent the same date, the chronology ID is compared to distinguish them.
596 * This step is needed to make the ordering "consistent with equals".
597 * <p>
598 * If all the date objects being compared are in the same chronology, then the
599 * additional chronology stage is not required and only the local date is used.
600 * To compare the dates of two {@code TemporalAccessor} instances, including dates
601 * in two different chronologies, use {@link ChronoField#EPOCH_DAY} as a comparator.
602 * <p>
603 * This default implementation performs the comparison defined above.
604 *
605 * @param other the other date to compare to, not null
606 * @return the comparator value, negative if less, positive if greater
607 */
608 @Override
609 public default int compareTo(ChronoLocalDate<?> other) {
610 int cmp = Long.compare(toEpochDay(), other.toEpochDay());
611 if (cmp == 0) {
612 cmp = getChronology().compareTo(other.getChronology());
613 }
614 return cmp;
615 }
616
617 /**
618 * Checks if this date is after the specified date ignoring the chronology.
619 * <p>
620 * This method differs from the comparison in {@link #compareTo} in that it
621 * only compares the underlying date and not the chronology.
622 * This allows dates in different calendar systems to be compared based
623 * on the time-line position.
624 * This is equivalent to using {@code date1.toEpochDay() > date2.toEpochDay()}.
625 * <p>
626 * This default implementation performs the comparison based on the epoch-day.
627 *
628 * @param other the other date to compare to, not null
629 * @return true if this is after the specified date
630 */
631 public default boolean isAfter(ChronoLocalDate<?> other) {
632 return this.toEpochDay() > other.toEpochDay();
633 }
634
635 /**
636 * Checks if this date is before the specified date ignoring the chronology.
637 * <p>
638 * This method differs from the comparison in {@link #compareTo} in that it
639 * only compares the underlying date and not the chronology.
640 * This allows dates in different calendar systems to be compared based
641 * on the time-line position.
642 * This is equivalent to using {@code date1.toEpochDay() < date2.toEpochDay()}.
643 * <p>
644 * This default implementation performs the comparison based on the epoch-day.
645 *
646 * @param other the other date to compare to, not null
647 * @return true if this is before the specified date
648 */
649 public default boolean isBefore(ChronoLocalDate<?> other) {
650 return this.toEpochDay() < other.toEpochDay();
651 }
652
653 /**
654 * Checks if this date is equal to the specified date ignoring the chronology.
655 * <p>
656 * This method differs from the comparison in {@link #compareTo} in that it
657 * only compares the underlying date and not the chronology.
658 * This allows dates in different calendar systems to be compared based
659 * on the time-line position.
660 * This is equivalent to using {@code date1.toEpochDay() == date2.toEpochDay()}.
661 * <p>
662 * This default implementation performs the comparison based on the epoch-day.
663 *
664 * @param other the other date to compare to, not null
665 * @return true if the underlying date is equal to the specified date
666 */
667 public default boolean isEqual(ChronoLocalDate<?> other) {
668 return this.toEpochDay() == other.toEpochDay();
669 }
670
671 //-----------------------------------------------------------------------
672 /**
673 * Checks if this date is equal to another date, including the chronology.
674 * <p>
675 * Compares this date with another ensuring that the date and chronology are the same.
676 * <p>
677 * To compare the dates of two {@code TemporalAccessor} instances, including dates
678 * in two different chronologies, use {@link ChronoField#EPOCH_DAY} as a comparator.
679 *
680 * @param obj the object to check, null returns false
681 * @return true if this is equal to the other date
682 */
683 @Override
684 boolean equals(Object obj);
685
686 /**
687 * A hash code for this date.
688 *
689 * @return a suitable hash code
690 */
691 @Override
692 int hashCode();
693
694 //-----------------------------------------------------------------------
695 /**
696 * Outputs this date as a {@code String}.
697 * <p>
698 * The output will include the full local date and the chronology ID.
699 *
700 * @return the formatted date, not null
701 */
702 @Override
703 String toString();
704
705 /**
706 * Outputs this date as a {@code String} using the formatter.
707 * <p>
708 * The default implementation must behave as follows:
709 * <pre>
710 * return formatter.format(this);
711 * </pre>
712 *
713 * @param formatter the formatter to use, not null
714 * @return the formatted date string, not null
715 * @throws DateTimeException if an error occurs during printing
716 */
717 public default String toString(DateTimeFormatter formatter) {
718 Objects.requireNonNull(formatter, "formatter");
719 return formatter.format(this);
720 }
721
722 }