1 /*
2 * Copyright (c) 2012, 2023, 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 static java.time.temporal.ChronoField.ERA;
65 import static java.time.temporal.ChronoField.YEAR;
66 import static java.time.temporal.ChronoField.YEAR_OF_ERA;
67 import static java.time.temporal.ChronoUnit.CENTURIES;
68 import static java.time.temporal.ChronoUnit.DECADES;
69 import static java.time.temporal.ChronoUnit.ERAS;
70 import static java.time.temporal.ChronoUnit.MILLENNIA;
71 import static java.time.temporal.ChronoUnit.YEARS;
72
73 import java.io.DataInput;
74 import java.io.DataOutput;
75 import java.io.IOException;
76 import java.io.InvalidObjectException;
77 import java.io.ObjectInputStream;
78 import java.io.Serializable;
79 import java.time.chrono.Chronology;
80 import java.time.chrono.IsoChronology;
81 import java.time.format.DateTimeFormatter;
82 import java.time.format.DateTimeFormatterBuilder;
83 import java.time.format.DateTimeParseException;
84 import java.time.format.SignStyle;
85 import java.time.temporal.ChronoField;
86 import java.time.temporal.ChronoUnit;
87 import java.time.temporal.Temporal;
88 import java.time.temporal.TemporalAccessor;
89 import java.time.temporal.TemporalAdjuster;
90 import java.time.temporal.TemporalAmount;
91 import java.time.temporal.TemporalField;
92 import java.time.temporal.TemporalQueries;
93 import java.time.temporal.TemporalQuery;
94 import java.time.temporal.TemporalUnit;
95 import java.time.temporal.UnsupportedTemporalTypeException;
96 import java.time.temporal.ValueRange;
97 import java.util.Objects;
98
99 /**
100 * A year in the ISO-8601 calendar system, such as {@code 2007}.
101 * <p>
102 * {@code Year} is an immutable date-time object that represents a year.
103 * Any field that can be derived from a year can be obtained.
104 * <p>
105 * <b>Note that years in the ISO chronology only align with years in the
106 * Gregorian-Julian system for modern years. Parts of Russia did not switch to the
107 * modern Gregorian/ISO rules until 1920.
108 * As such, historical years must be treated with caution.</b>
109 * <p>
110 * This class does not store or represent a month, day, time or time-zone.
111 * For example, the value "2007" can be stored in a {@code Year}.
112 * <p>
113 * Years represented by this class follow the ISO-8601 standard and use
114 * the proleptic numbering system. Year 1 is preceded by year 0, then by year -1.
115 * <p>
116 * The ISO-8601 calendar system is the modern civil calendar system used today
117 * in most of the world. It is equivalent to the proleptic Gregorian calendar
118 * system, in which today's rules for leap years are applied for all time.
119 * For most applications written today, the ISO-8601 rules are entirely suitable.
120 * However, any application that makes use of historical dates, and requires them
121 * to be accurate will find the ISO-8601 approach unsuitable.
122 * <p>
123 * This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
124 * class; programmers should treat instances that are
125 * {@linkplain #equals(Object) equal} as interchangeable and should not
126 * use instances for synchronization, or unpredictable behavior may
127 * occur. For example, in a future release, synchronization may fail.
128 * The {@code equals} method should be used for comparisons.
129 *
130 * @implSpec
131 * This class is immutable and thread-safe.
132 *
133 * @since 1.8
134 */
135 @jdk.internal.ValueBased
136 public final class Year
137 implements Temporal, TemporalAdjuster, Comparable<Year>, Serializable {
138
139 /**
140 * The minimum supported year, '-999,999,999'.
141 */
142 public static final int MIN_VALUE = -999_999_999;
143 /**
144 * The maximum supported year, '+999,999,999'.
145 */
146 public static final int MAX_VALUE = 999_999_999;
147
148 /**
149 * Serialization version.
150 */
151 @java.io.Serial
152 private static final long serialVersionUID = -23038383694477807L;
153 /**
154 * Parser.
155 */
156 private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder()
157 .parseLenient()
158 .appendValue(YEAR, 1, 10, SignStyle.NORMAL)
159 .toFormatter();
160
161 /**
162 * The year being represented.
163 */
164 private final int year;
165
166 //-----------------------------------------------------------------------
167 /**
168 * Obtains the current year from the system clock in the default time-zone.
169 * <p>
170 * This will query the {@link Clock#systemDefaultZone() system clock} in the default
171 * time-zone to obtain the current year.
172 * <p>
173 * Using this method will prevent the ability to use an alternate clock for testing
174 * because the clock is hard-coded.
175 *
176 * @return the current year using the system clock and default time-zone, not null
177 */
178 public static Year now() {
179 return now(Clock.systemDefaultZone());
180 }
181
182 /**
183 * Obtains the current year from the system clock in the specified time-zone.
184 * <p>
185 * This will query the {@link Clock#system(ZoneId) system clock} to obtain the current year.
186 * Specifying the time-zone avoids dependence on the default time-zone.
187 * <p>
188 * Using this method will prevent the ability to use an alternate clock for testing
189 * because the clock is hard-coded.
190 *
191 * @param zone the zone ID to use, not null
192 * @return the current year using the system clock, not null
193 */
194 public static Year now(ZoneId zone) {
195 return now(Clock.system(zone));
196 }
197
198 /**
199 * Obtains the current year from the specified clock.
200 * <p>
201 * This will query the specified clock to obtain the current year.
202 * Using this method allows the use of an alternate clock for testing.
203 * The alternate clock may be introduced using {@link Clock dependency injection}.
204 *
205 * @param clock the clock to use, not null
206 * @return the current year, not null
207 */
208 public static Year now(Clock clock) {
209 final LocalDate now = LocalDate.now(clock); // called once
210 return Year.of(now.getYear());
211 }
212
213 //-----------------------------------------------------------------------
214 /**
215 * Obtains an instance of {@code Year}.
216 * <p>
217 * This method accepts a year value from the proleptic ISO calendar system.
218 * <p>
219 * The year 2AD/CE is represented by 2.<br>
220 * The year 1AD/CE is represented by 1.<br>
221 * The year 1BC/BCE is represented by 0.<br>
222 * The year 2BC/BCE is represented by -1.<br>
223 *
224 * @param isoYear the ISO proleptic year to represent, from {@code MIN_VALUE} to {@code MAX_VALUE}
225 * @return the year, not null
226 * @throws DateTimeException if the field is invalid
227 */
228 public static Year of(int isoYear) {
229 YEAR.checkValidValue(isoYear);
230 return new Year(isoYear);
231 }
232
233 //-----------------------------------------------------------------------
234 /**
235 * Obtains an instance of {@code Year} from a temporal object.
236 * <p>
237 * This obtains a year based on the specified temporal.
238 * A {@code TemporalAccessor} represents an arbitrary set of date and time information,
239 * which this factory converts to an instance of {@code Year}.
240 * <p>
241 * The conversion extracts the {@link ChronoField#YEAR year} field.
242 * The extraction is only permitted if the temporal object has an ISO
243 * chronology, or can be converted to a {@code LocalDate}.
244 * <p>
245 * This method matches the signature of the functional interface {@link TemporalQuery}
246 * allowing it to be used as a query via method reference, {@code Year::from}.
247 *
248 * @param temporal the temporal object to convert, not null
249 * @return the year, not null
250 * @throws DateTimeException if unable to convert to a {@code Year}
251 */
252 public static Year from(TemporalAccessor temporal) {
253 if (temporal instanceof Year) {
254 return (Year) temporal;
255 }
256 Objects.requireNonNull(temporal, "temporal");
257 try {
258 if (IsoChronology.INSTANCE.equals(Chronology.from(temporal)) == false) {
259 temporal = LocalDate.from(temporal);
260 }
261 return of(temporal.get(YEAR));
262 } catch (DateTimeException ex) {
263 throw new DateTimeException("Unable to obtain Year from TemporalAccessor: " +
264 temporal + " of type " + temporal.getClass().getName(), ex);
265 }
266 }
267
268 //-----------------------------------------------------------------------
269 /**
270 * Obtains an instance of {@code Year} from a text string such as {@code 2007}.
271 * <p>
272 * The string must represent a valid year.
273 *
274 * @param text the text to parse such as "2007", not null
275 * @return the parsed year, not null
276 * @throws DateTimeParseException if the text cannot be parsed
277 */
278 public static Year parse(CharSequence text) {
279 return parse(text, PARSER);
280 }
281
282 /**
283 * Obtains an instance of {@code Year} from a text string using a specific formatter.
284 * <p>
285 * The text is parsed using the formatter, returning a year.
286 *
287 * @param text the text to parse, not null
288 * @param formatter the formatter to use, not null
289 * @return the parsed year, not null
290 * @throws DateTimeParseException if the text cannot be parsed
291 */
292 public static Year parse(CharSequence text, DateTimeFormatter formatter) {
293 Objects.requireNonNull(formatter, "formatter");
294 return formatter.parse(text, Year::from);
295 }
296
297 //-------------------------------------------------------------------------
298 /**
299 * Checks if the year is a leap year, according to the ISO proleptic
300 * calendar system rules.
301 * <p>
302 * This method applies the current rules for leap years across the whole time-line.
303 * In general, a year is a leap year if it is divisible by four without
304 * remainder. However, years divisible by 100, are not leap years, with
305 * the exception of years divisible by 400 which are.
306 * <p>
307 * For example, 1904 is a leap year it is divisible by 4.
308 * 1900 was not a leap year as it is divisible by 100, however 2000 was a
309 * leap year as it is divisible by 400.
310 * <p>
311 * The calculation is proleptic - applying the same rules into the far future and far past.
312 * This is historically inaccurate, but is correct for the ISO-8601 standard.
313 *
314 * @param year the year to check
315 * @return true if the year is leap, false otherwise
316 */
317 public static boolean isLeap(long year) {
318 // A year that is a multiple of 100, 200 and 300 is not divisible by 16, but 400 is.
319 // So for a year that's divisible by 4, checking that it's also divisible by 16
320 // is sufficient to determine it must be a leap year.
321 return (year & 15) == 0 ? (year & 3) == 0 : (year & 3) == 0 && year % 100 != 0;
322 }
323
324 //-----------------------------------------------------------------------
325 /**
326 * Constructor.
327 *
328 * @param year the year to represent
329 */
330 private Year(int year) {
331 this.year = year;
332 }
333
334 //-----------------------------------------------------------------------
335 /**
336 * Gets the year value.
337 * <p>
338 * The year returned by this method is proleptic as per {@code get(YEAR)}.
339 *
340 * @return the year, {@code MIN_VALUE} to {@code MAX_VALUE}
341 */
342 public int getValue() {
343 return year;
344 }
345
346 //-----------------------------------------------------------------------
347 /**
348 * Checks if the specified field is supported.
349 * <p>
350 * This checks if this year can be queried for the specified field.
351 * If false, then calling the {@link #range(TemporalField) range},
352 * {@link #get(TemporalField) get} and {@link #with(TemporalField, long)}
353 * methods will throw an exception.
354 * <p>
355 * If the field is a {@link ChronoField} then the query is implemented here.
356 * The supported fields are:
357 * <ul>
358 * <li>{@code YEAR_OF_ERA}
359 * <li>{@code YEAR}
360 * <li>{@code ERA}
361 * </ul>
362 * All other {@code ChronoField} instances will return false.
363 * <p>
364 * If the field is not a {@code ChronoField}, then the result of this method
365 * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)}
366 * passing {@code this} as the argument.
367 * Whether the field is supported is determined by the field.
368 *
369 * @param field the field to check, null returns false
370 * @return true if the field is supported on this year, false if not
371 */
372 @Override
373 public boolean isSupported(TemporalField field) {
374 if (field instanceof ChronoField) {
375 return field == YEAR || field == YEAR_OF_ERA || field == ERA;
376 }
377 return field != null && field.isSupportedBy(this);
378 }
379
380 /**
381 * Checks if the specified unit is supported.
382 * <p>
383 * This checks if the specified unit can be added to, or subtracted from, this year.
384 * If false, then calling the {@link #plus(long, TemporalUnit)} and
385 * {@link #minus(long, TemporalUnit) minus} methods will throw an exception.
386 * <p>
387 * If the unit is a {@link ChronoUnit} then the query is implemented here.
388 * The supported units are:
389 * <ul>
390 * <li>{@code YEARS}
391 * <li>{@code DECADES}
392 * <li>{@code CENTURIES}
393 * <li>{@code MILLENNIA}
394 * <li>{@code ERAS}
395 * </ul>
396 * All other {@code ChronoUnit} instances will return false.
397 * <p>
398 * If the unit is not a {@code ChronoUnit}, then the result of this method
399 * is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)}
400 * passing {@code this} as the argument.
401 * Whether the unit is supported is determined by the unit.
402 *
403 * @param unit the unit to check, null returns false
404 * @return true if the unit can be added/subtracted, false if not
405 */
406 @Override
407 public boolean isSupported(TemporalUnit unit) {
408 if (unit instanceof ChronoUnit) {
409 return unit == YEARS || unit == DECADES || unit == CENTURIES || unit == MILLENNIA || unit == ERAS;
410 }
411 return unit != null && unit.isSupportedBy(this);
412 }
413
414 //-----------------------------------------------------------------------
415 /**
416 * Gets the range of valid values for the specified field.
417 * <p>
418 * The range object expresses the minimum and maximum valid values for a field.
419 * This year is used to enhance the accuracy of the returned range.
420 * If it is not possible to return the range, because the field is not supported
421 * or for some other reason, an exception is thrown.
422 * <p>
423 * If the field is a {@link ChronoField} then the query is implemented here.
424 * The {@link #isSupported(TemporalField) supported fields} will return
425 * appropriate range instances.
426 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
427 * <p>
428 * If the field is not a {@code ChronoField}, then the result of this method
429 * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)}
430 * passing {@code this} as the argument.
431 * Whether the range can be obtained is determined by the field.
432 *
433 * @param field the field to query the range for, not null
434 * @return the range of valid values for the field, not null
435 * @throws DateTimeException if the range for the field cannot be obtained
436 * @throws UnsupportedTemporalTypeException if the field is not supported
437 */
438 @Override
439 public ValueRange range(TemporalField field) {
440 if (field == YEAR_OF_ERA) {
441 return (year <= 0 ? ValueRange.of(1, MAX_VALUE + 1) : ValueRange.of(1, MAX_VALUE));
442 }
443 return Temporal.super.range(field);
444 }
445
446 /**
447 * Gets the value of the specified field from this year as an {@code int}.
448 * <p>
449 * This queries this year for the value of the specified field.
450 * The returned value will always be within the valid range of values for the field.
451 * If it is not possible to return the value, because the field is not supported
452 * or for some other reason, an exception is thrown.
453 * <p>
454 * If the field is a {@link ChronoField} then the query is implemented here.
455 * The {@link #isSupported(TemporalField) supported fields} will return valid
456 * values based on this year.
457 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
458 * <p>
459 * If the field is not a {@code ChronoField}, then the result of this method
460 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
461 * passing {@code this} as the argument. Whether the value can be obtained,
462 * and what the value represents, is determined by the field.
463 *
464 * @param field the field to get, not null
465 * @return the value for the field
466 * @throws DateTimeException if a value for the field cannot be obtained or
467 * the value is outside the range of valid values for the field
468 * @throws UnsupportedTemporalTypeException if the field is not supported or
469 * the range of values exceeds an {@code int}
470 * @throws ArithmeticException if numeric overflow occurs
471 */
472 @Override // override for Javadoc
473 public int get(TemporalField field) {
474 return range(field).checkValidIntValue(getLong(field), field);
475 }
476
477 /**
478 * Gets the value of the specified field from this year as a {@code long}.
479 * <p>
480 * This queries this year for the value of the specified field.
481 * If it is not possible to return the value, because the field is not supported
482 * or for some other reason, an exception is thrown.
483 * <p>
484 * If the field is a {@link ChronoField} then the query is implemented here.
485 * The {@link #isSupported(TemporalField) supported fields} will return valid
486 * values based on this year.
487 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
488 * <p>
489 * If the field is not a {@code ChronoField}, then the result of this method
490 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
491 * passing {@code this} as the argument. Whether the value can be obtained,
492 * and what the value represents, is determined by the field.
493 *
494 * @param field the field to get, not null
495 * @return the value for the field
496 * @throws DateTimeException if a value for the field cannot be obtained
497 * @throws UnsupportedTemporalTypeException if the field is not supported
498 * @throws ArithmeticException if numeric overflow occurs
499 */
500 @Override
501 public long getLong(TemporalField field) {
502 if (field instanceof ChronoField chronoField) {
503 return switch (chronoField) {
504 case YEAR_OF_ERA -> year < 1 ? 1 - year : year;
505 case YEAR -> year;
506 case ERA -> year < 1 ? 0 : 1;
507 default -> throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
508 };
509 }
510 return field.getFrom(this);
511 }
512
513 //-----------------------------------------------------------------------
514 /**
515 * Checks if the year is a leap year, according to the ISO proleptic
516 * calendar system rules.
517 * <p>
518 * This method applies the current rules for leap years across the whole time-line.
519 * In general, a year is a leap year if it is divisible by four without
520 * remainder. However, years divisible by 100, are not leap years, with
521 * the exception of years divisible by 400 which are.
522 * <p>
523 * For example, 1904 is a leap year it is divisible by 4.
524 * 1900 was not a leap year as it is divisible by 100, however 2000 was a
525 * leap year as it is divisible by 400.
526 * <p>
527 * The calculation is proleptic - applying the same rules into the far future and far past.
528 * This is historically inaccurate, but is correct for the ISO-8601 standard.
529 *
530 * @return true if the year is leap, false otherwise
531 */
532 public boolean isLeap() {
533 return Year.isLeap(year);
534 }
535
536 /**
537 * Checks if the month-day is valid for this year.
538 * <p>
539 * This method checks whether this year and the input month and day form
540 * a valid date.
541 *
542 * @param monthDay the month-day to validate, null returns false
543 * @return true if the month and day are valid for this year
544 */
545 public boolean isValidMonthDay(MonthDay monthDay) {
546 return monthDay != null && monthDay.isValidYear(year);
547 }
548
549 /**
550 * Gets the length of this year in days.
551 *
552 * @return the length of this year in days, 365 or 366
553 */
554 public int length() {
555 return isLeap() ? 366 : 365;
556 }
557
558 //-----------------------------------------------------------------------
559 /**
560 * Returns an adjusted copy of this year.
561 * <p>
562 * This returns a {@code Year}, based on this one, with the year adjusted.
563 * The adjustment takes place using the specified adjuster strategy object.
564 * Read the documentation of the adjuster to understand what adjustment will be made.
565 * <p>
566 * The result of this method is obtained by invoking the
567 * {@link TemporalAdjuster#adjustInto(Temporal)} method on the
568 * specified adjuster passing {@code this} as the argument.
569 * <p>
570 * This instance is immutable and unaffected by this method call.
571 *
572 * @param adjuster the adjuster to use, not null
573 * @return a {@code Year} based on {@code this} with the adjustment made, not null
574 * @throws DateTimeException if the adjustment cannot be made
575 * @throws ArithmeticException if numeric overflow occurs
576 */
577 @Override
578 public Year with(TemporalAdjuster adjuster) {
579 return (Year) adjuster.adjustInto(this);
580 }
581
582 /**
583 * Returns a copy of this year with the specified field set to a new value.
584 * <p>
585 * This returns a {@code Year}, based on this one, with the value
586 * for the specified field changed.
587 * If it is not possible to set the value, because the field is not supported or for
588 * some other reason, an exception is thrown.
589 * <p>
590 * If the field is a {@link ChronoField} then the adjustment is implemented here.
591 * The supported fields behave as follows:
592 * <ul>
593 * <li>{@code YEAR_OF_ERA} -
594 * Returns a {@code Year} with the specified year-of-era
595 * The era will be unchanged.
596 * <li>{@code YEAR} -
597 * Returns a {@code Year} with the specified year.
598 * This completely replaces the date and is equivalent to {@link #of(int)}.
599 * <li>{@code ERA} -
600 * Returns a {@code Year} with the specified era.
601 * The year-of-era will be unchanged.
602 * </ul>
603 * <p>
604 * In all cases, if the new value is outside the valid range of values for the field
605 * then a {@code DateTimeException} will be thrown.
606 * <p>
607 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
608 * <p>
609 * If the field is not a {@code ChronoField}, then the result of this method
610 * is obtained by invoking {@code TemporalField.adjustInto(Temporal, long)}
611 * passing {@code this} as the argument. In this case, the field determines
612 * whether and how to adjust the instant.
613 * <p>
614 * This instance is immutable and unaffected by this method call.
615 *
616 * @param field the field to set in the result, not null
617 * @param newValue the new value of the field in the result
618 * @return a {@code Year} based on {@code this} with the specified field set, not null
619 * @throws DateTimeException if the field cannot be set
620 * @throws UnsupportedTemporalTypeException if the field is not supported
621 * @throws ArithmeticException if numeric overflow occurs
622 */
623 @Override
624 public Year with(TemporalField field, long newValue) {
625 if (field instanceof ChronoField chronoField) {
626 chronoField.checkValidValue(newValue);
627 return switch (chronoField) {
628 case YEAR_OF_ERA -> Year.of((int) (year < 1 ? 1 - newValue : newValue));
629 case YEAR -> Year.of((int) newValue);
630 case ERA -> getLong(ERA) == newValue ? this : Year.of(1 - year);
631 default -> throw new UnsupportedTemporalTypeException("Unsupported field: " + field);
632 };
633 }
634 return field.adjustInto(this, newValue);
635 }
636
637 //-----------------------------------------------------------------------
638 /**
639 * Returns a copy of this year with the specified amount added.
640 * <p>
641 * This returns a {@code Year}, based on this one, with the specified amount added.
642 * The amount is typically {@link Period} but may be any other type implementing
643 * the {@link TemporalAmount} interface.
644 * <p>
645 * The calculation is delegated to the amount object by calling
646 * {@link TemporalAmount#addTo(Temporal)}. The amount implementation is free
647 * to implement the addition in any way it wishes, however it typically
648 * calls back to {@link #plus(long, TemporalUnit)}. Consult the documentation
649 * of the amount implementation to determine if it can be successfully added.
650 * <p>
651 * This instance is immutable and unaffected by this method call.
652 *
653 * @param amountToAdd the amount to add, not null
654 * @return a {@code Year} based on this year with the addition made, not null
655 * @throws DateTimeException if the addition cannot be made
656 * @throws ArithmeticException if numeric overflow occurs
657 */
658 @Override
659 public Year plus(TemporalAmount amountToAdd) {
660 return (Year) amountToAdd.addTo(this);
661 }
662
663 /**
664 * Returns a copy of this year with the specified amount added.
665 * <p>
666 * This returns a {@code Year}, based on this one, with the amount
667 * in terms of the unit added. If it is not possible to add the amount, because the
668 * unit is not supported or for some other reason, an exception is thrown.
669 * <p>
670 * If the field is a {@link ChronoUnit} then the addition is implemented here.
671 * The supported fields behave as follows:
672 * <ul>
673 * <li>{@code YEARS} -
674 * Returns a {@code Year} with the specified number of years added.
675 * This is equivalent to {@link #plusYears(long)}.
676 * <li>{@code DECADES} -
677 * Returns a {@code Year} with the specified number of decades added.
678 * This is equivalent to calling {@link #plusYears(long)} with the amount
679 * multiplied by 10.
680 * <li>{@code CENTURIES} -
681 * Returns a {@code Year} with the specified number of centuries added.
682 * This is equivalent to calling {@link #plusYears(long)} with the amount
683 * multiplied by 100.
684 * <li>{@code MILLENNIA} -
685 * Returns a {@code Year} with the specified number of millennia added.
686 * This is equivalent to calling {@link #plusYears(long)} with the amount
687 * multiplied by 1,000.
688 * <li>{@code ERAS} -
689 * Returns a {@code Year} with the specified number of eras added.
690 * Only two eras are supported so the amount must be one, zero or minus one.
691 * If the amount is non-zero then the year is changed such that the year-of-era
692 * is unchanged.
693 * </ul>
694 * <p>
695 * All other {@code ChronoUnit} instances will throw an {@code UnsupportedTemporalTypeException}.
696 * <p>
697 * If the field is not a {@code ChronoUnit}, then the result of this method
698 * is obtained by invoking {@code TemporalUnit.addTo(Temporal, long)}
699 * passing {@code this} as the argument. In this case, the unit determines
700 * whether and how to perform the addition.
701 * <p>
702 * This instance is immutable and unaffected by this method call.
703 *
704 * @param amountToAdd the amount of the unit to add to the result, may be negative
705 * @param unit the unit of the amount to add, not null
706 * @return a {@code Year} based on this year with the specified amount added, not null
707 * @throws DateTimeException if the addition cannot be made
708 * @throws UnsupportedTemporalTypeException if the unit is not supported
709 * @throws ArithmeticException if numeric overflow occurs
710 */
711 @Override
712 public Year plus(long amountToAdd, TemporalUnit unit) {
713 if (unit instanceof ChronoUnit chronoUnit) {
714 return switch (chronoUnit) {
715 case YEARS -> plusYears(amountToAdd);
716 case DECADES -> plusYears(Math.multiplyExact(amountToAdd, 10));
717 case CENTURIES -> plusYears(Math.multiplyExact(amountToAdd, 100));
718 case MILLENNIA -> plusYears(Math.multiplyExact(amountToAdd, 1000));
719 case ERAS -> with(ERA, Math.addExact(getLong(ERA), amountToAdd));
720 default -> throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
721 };
722 }
723 return unit.addTo(this, amountToAdd);
724 }
725
726 /**
727 * Returns a copy of this {@code Year} with the specified number of years added.
728 * <p>
729 * This instance is immutable and unaffected by this method call.
730 *
731 * @param yearsToAdd the years to add, may be negative
732 * @return a {@code Year} based on this year with the years added, not null
733 * @throws DateTimeException if the result exceeds the supported range
734 */
735 public Year plusYears(long yearsToAdd) {
736 if (yearsToAdd == 0) {
737 return this;
738 }
739 return of(YEAR.checkValidIntValue(year + yearsToAdd)); // overflow safe
740 }
741
742 //-----------------------------------------------------------------------
743 /**
744 * Returns a copy of this year with the specified amount subtracted.
745 * <p>
746 * This returns a {@code Year}, based on this one, with the specified amount subtracted.
747 * The amount is typically {@link Period} but may be any other type implementing
748 * the {@link TemporalAmount} interface.
749 * <p>
750 * The calculation is delegated to the amount object by calling
751 * {@link TemporalAmount#subtractFrom(Temporal)}. The amount implementation is free
752 * to implement the subtraction in any way it wishes, however it typically
753 * calls back to {@link #minus(long, TemporalUnit)}. Consult the documentation
754 * of the amount implementation to determine if it can be successfully subtracted.
755 * <p>
756 * This instance is immutable and unaffected by this method call.
757 *
758 * @param amountToSubtract the amount to subtract, not null
759 * @return a {@code Year} based on this year with the subtraction made, not null
760 * @throws DateTimeException if the subtraction cannot be made
761 * @throws ArithmeticException if numeric overflow occurs
762 */
763 @Override
764 public Year minus(TemporalAmount amountToSubtract) {
765 return (Year) amountToSubtract.subtractFrom(this);
766 }
767
768 /**
769 * Returns a copy of this year with the specified amount subtracted.
770 * <p>
771 * This returns a {@code Year}, based on this one, with the amount
772 * in terms of the unit subtracted. If it is not possible to subtract the amount,
773 * because the unit is not supported or for some other reason, an exception is thrown.
774 * <p>
775 * This method is equivalent to {@link #plus(long, TemporalUnit)} with the amount negated.
776 * See that method for a full description of how addition, and thus subtraction, works.
777 * <p>
778 * This instance is immutable and unaffected by this method call.
779 *
780 * @param amountToSubtract the amount of the unit to subtract from the result, may be negative
781 * @param unit the unit of the amount to subtract, not null
782 * @return a {@code Year} based on this year with the specified amount subtracted, not null
783 * @throws DateTimeException if the subtraction cannot be made
784 * @throws UnsupportedTemporalTypeException if the unit is not supported
785 * @throws ArithmeticException if numeric overflow occurs
786 */
787 @Override
788 public Year minus(long amountToSubtract, TemporalUnit unit) {
789 return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
790 }
791
792 /**
793 * Returns a copy of this {@code Year} with the specified number of years subtracted.
794 * <p>
795 * This instance is immutable and unaffected by this method call.
796 *
797 * @param yearsToSubtract the years to subtract, may be negative
798 * @return a {@code Year} based on this year with the year subtracted, not null
799 * @throws DateTimeException if the result exceeds the supported range
800 */
801 public Year minusYears(long yearsToSubtract) {
802 return (yearsToSubtract == Long.MIN_VALUE ? plusYears(Long.MAX_VALUE).plusYears(1) : plusYears(-yearsToSubtract));
803 }
804
805 //-----------------------------------------------------------------------
806 /**
807 * Queries this year using the specified query.
808 * <p>
809 * This queries this year using the specified query strategy object.
810 * The {@code TemporalQuery} object defines the logic to be used to
811 * obtain the result. Read the documentation of the query to understand
812 * what the result of this method will be.
813 * <p>
814 * The result of this method is obtained by invoking the
815 * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
816 * specified query passing {@code this} as the argument.
817 *
818 * @param <R> the type of the result
819 * @param query the query to invoke, not null
820 * @return the query result, null may be returned (defined by the query)
821 * @throws DateTimeException if unable to query (defined by the query)
822 * @throws ArithmeticException if numeric overflow occurs (defined by the query)
823 */
824 @SuppressWarnings("unchecked")
825 @Override
826 public <R> R query(TemporalQuery<R> query) {
827 if (query == TemporalQueries.chronology()) {
828 return (R) IsoChronology.INSTANCE;
829 } else if (query == TemporalQueries.precision()) {
830 return (R) YEARS;
831 }
832 return Temporal.super.query(query);
833 }
834
835 /**
836 * Adjusts the specified temporal object to have this year.
837 * <p>
838 * This returns a temporal object of the same observable type as the input
839 * with the year changed to be the same as this.
840 * <p>
841 * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
842 * passing {@link ChronoField#YEAR} as the field.
843 * If the specified temporal object does not use the ISO calendar system then
844 * a {@code DateTimeException} is thrown.
845 * <p>
846 * In most cases, it is clearer to reverse the calling pattern by using
847 * {@link Temporal#with(TemporalAdjuster)}:
848 * <pre>
849 * // these two lines are equivalent, but the second approach is recommended
850 * temporal = thisYear.adjustInto(temporal);
851 * temporal = temporal.with(thisYear);
852 * </pre>
853 * <p>
854 * This instance is immutable and unaffected by this method call.
855 *
856 * @param temporal the target object to be adjusted, not null
857 * @return the adjusted object, not null
858 * @throws DateTimeException if unable to make the adjustment
859 * @throws ArithmeticException if numeric overflow occurs
860 */
861 @Override
862 public Temporal adjustInto(Temporal temporal) {
863 if (Chronology.from(temporal).equals(IsoChronology.INSTANCE) == false) {
864 throw new DateTimeException("Adjustment only supported on ISO date-time");
865 }
866 return temporal.with(YEAR, year);
867 }
868
869 /**
870 * Calculates the amount of time until another year in terms of the specified unit.
871 * <p>
872 * This calculates the amount of time between two {@code Year}
873 * objects in terms of a single {@code TemporalUnit}.
874 * The start and end points are {@code this} and the specified year.
875 * The result will be negative if the end is before the start.
876 * The {@code Temporal} passed to this method is converted to a
877 * {@code Year} using {@link #from(TemporalAccessor)}.
878 * For example, the amount in decades between two year can be calculated
879 * using {@code startYear.until(endYear, DECADES)}.
880 * <p>
881 * The calculation returns a whole number, representing the number of
882 * complete units between the two years.
883 * For example, the amount in decades between 2012 and 2031
884 * will only be one decade as it is one year short of two decades.
885 * <p>
886 * There are two equivalent ways of using this method.
887 * The first is to invoke this method.
888 * The second is to use {@link TemporalUnit#between(Temporal, Temporal)}:
889 * <pre>
890 * // these two lines are equivalent
891 * amount = start.until(end, YEARS);
892 * amount = YEARS.between(start, end);
893 * </pre>
894 * The choice should be made based on which makes the code more readable.
895 * <p>
896 * The calculation is implemented in this method for {@link ChronoUnit}.
897 * The units {@code YEARS}, {@code DECADES}, {@code CENTURIES},
898 * {@code MILLENNIA} and {@code ERAS} are supported.
899 * Other {@code ChronoUnit} values will throw an exception.
900 * <p>
901 * If the unit is not a {@code ChronoUnit}, then the result of this method
902 * is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)}
903 * passing {@code this} as the first argument and the converted input temporal
904 * as the second argument.
905 * <p>
906 * This instance is immutable and unaffected by this method call.
907 *
908 * @param endExclusive the end date, exclusive, which is converted to a {@code Year}, not null
909 * @param unit the unit to measure the amount in, not null
910 * @return the amount of time between this year and the end year
911 * @throws DateTimeException if the amount cannot be calculated, or the end
912 * temporal cannot be converted to a {@code Year}
913 * @throws UnsupportedTemporalTypeException if the unit is not supported
914 * @throws ArithmeticException if numeric overflow occurs
915 */
916 @Override
917 public long until(Temporal endExclusive, TemporalUnit unit) {
918 Year end = Year.from(endExclusive);
919 if (unit instanceof ChronoUnit chronoUnit) {
920 long yearsUntil = ((long) end.year) - year; // no overflow
921 return switch (chronoUnit) {
922 case YEARS -> yearsUntil;
923 case DECADES -> yearsUntil / 10;
924 case CENTURIES -> yearsUntil / 100;
925 case MILLENNIA -> yearsUntil / 1000;
926 case ERAS -> end.getLong(ERA) - getLong(ERA);
927 default -> throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
928 };
929 }
930 return unit.between(this, end);
931 }
932
933 /**
934 * Formats this year using the specified formatter.
935 * <p>
936 * This year will be passed to the formatter to produce a string.
937 *
938 * @param formatter the formatter to use, not null
939 * @return the formatted year string, not null
940 * @throws DateTimeException if an error occurs during printing
941 */
942 public String format(DateTimeFormatter formatter) {
943 Objects.requireNonNull(formatter, "formatter");
944 return formatter.format(this);
945 }
946
947 //-----------------------------------------------------------------------
948 /**
949 * Combines this year with a day-of-year to create a {@code LocalDate}.
950 * <p>
951 * This returns a {@code LocalDate} formed from this year and the specified day-of-year.
952 * <p>
953 * The day-of-year value 366 is only valid in a leap year.
954 *
955 * @param dayOfYear the day-of-year to use, from 1 to 365-366
956 * @return the local date formed from this year and the specified date of year, not null
957 * @throws DateTimeException if the day of year is zero or less, 366 or greater or equal
958 * to 366 and this is not a leap year
959 */
960 public LocalDate atDay(int dayOfYear) {
961 return LocalDate.ofYearDay(year, dayOfYear);
962 }
963
964 /**
965 * Combines this year with a month to create a {@code YearMonth}.
966 * <p>
967 * This returns a {@code YearMonth} formed from this year and the specified month.
968 * All possible combinations of year and month are valid.
969 * <p>
970 * This method can be used as part of a chain to produce a date:
971 * <pre>
972 * LocalDate date = year.atMonth(month).atDay(day);
973 * </pre>
974 *
975 * @param month the month-of-year to use, not null
976 * @return the year-month formed from this year and the specified month, not null
977 */
978 public YearMonth atMonth(Month month) {
979 return YearMonth.of(year, month);
980 }
981
982 /**
983 * Combines this year with a month to create a {@code YearMonth}.
984 * <p>
985 * This returns a {@code YearMonth} formed from this year and the specified month.
986 * All possible combinations of year and month are valid.
987 * <p>
988 * This method can be used as part of a chain to produce a date:
989 * <pre>
990 * LocalDate date = year.atMonth(month).atDay(day);
991 * </pre>
992 *
993 * @param month the month-of-year to use, from 1 (January) to 12 (December)
994 * @return the year-month formed from this year and the specified month, not null
995 * @throws DateTimeException if the month is invalid
996 */
997 public YearMonth atMonth(int month) {
998 return YearMonth.of(year, month);
999 }
1000
1001 /**
1002 * Combines this year with a month-day to create a {@code LocalDate}.
1003 * <p>
1004 * This returns a {@code LocalDate} formed from this year and the specified month-day.
1005 * <p>
1006 * A month-day of February 29th will be adjusted to February 28th in the resulting
1007 * date if the year is not a leap year.
1008 *
1009 * @param monthDay the month-day to use, not null
1010 * @return the local date formed from this year and the specified month-day, not null
1011 */
1012 public LocalDate atMonthDay(MonthDay monthDay) {
1013 return monthDay.atYear(year);
1014 }
1015
1016 //-----------------------------------------------------------------------
1017 /**
1018 * Compares this year to another year.
1019 * <p>
1020 * The comparison is based on the value of the year.
1021 * It is "consistent with equals", as defined by {@link Comparable}.
1022 *
1023 * @param other the other year to compare to, not null
1024 * @return the comparator value, that is less than zero if this is before {@code other},
1025 * zero if they are equal, or greater than zero if this is after {@code other}
1026 * @see #isBefore
1027 * @see #isAfter
1028 */
1029 @Override
1030 public int compareTo(Year other) {
1031 return year - other.year;
1032 }
1033
1034 /**
1035 * Checks if this year is after the specified year.
1036 *
1037 * @param other the other year to compare to, not null
1038 * @return true if this is after the specified year
1039 */
1040 public boolean isAfter(Year other) {
1041 return year > other.year;
1042 }
1043
1044 /**
1045 * Checks if this year is before the specified year.
1046 *
1047 * @param other the other year to compare to, not null
1048 * @return true if this point is before the specified year
1049 */
1050 public boolean isBefore(Year other) {
1051 return year < other.year;
1052 }
1053
1054 //-----------------------------------------------------------------------
1055 /**
1056 * Checks if this year is equal to another year.
1057 * <p>
1058 * The comparison is based on the time-line position of the years.
1059 *
1060 * @param obj the object to check, null returns false
1061 * @return true if this is equal to the other year
1062 */
1063 @Override
1064 public boolean equals(Object obj) {
1065 if (this == obj) {
1066 return true;
1067 }
1068 if (obj instanceof Year) {
1069 return year == ((Year) obj).year;
1070 }
1071 return false;
1072 }
1073
1074 /**
1075 * A hash code for this year.
1076 *
1077 * @return a suitable hash code
1078 */
1079 @Override
1080 public int hashCode() {
1081 return year;
1082 }
1083
1084 //-----------------------------------------------------------------------
1085 /**
1086 * Outputs this year as a {@code String}.
1087 *
1088 * @return a string representation of this year, not null
1089 */
1090 @Override
1091 public String toString() {
1092 return Integer.toString(year);
1093 }
1094
1095 //-----------------------------------------------------------------------
1096 /**
1097 * Writes the object using a
1098 * <a href="{@docRoot}/serialized-form.html#java.time.Ser">dedicated serialized form</a>.
1099 * @serialData
1100 * <pre>
1101 * out.writeByte(11); // identifies a Year
1102 * out.writeInt(year);
1103 * </pre>
1104 *
1105 * @return the instance of {@code Ser}, not null
1106 */
1107 @java.io.Serial
1108 private Object writeReplace() {
1109 return new Ser(Ser.YEAR_TYPE, this);
1110 }
1111
1112 /**
1113 * Defend against malicious streams.
1114 *
1115 * @param s the stream to read
1116 * @throws InvalidObjectException always
1117 */
1118 @java.io.Serial
1119 private void readObject(ObjectInputStream s) throws InvalidObjectException {
1120 throw new InvalidObjectException("Deserialization via serialization delegate");
1121 }
1122
1123 void writeExternal(DataOutput out) throws IOException {
1124 out.writeInt(year);
1125 }
1126
1127 static Year readExternal(DataInput in) throws IOException {
1128 return Year.of(in.readInt());
1129 }
1130
1131 }