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
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.temporal;
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.YEARS;
68
69 import java.io.DataInput;
70 import java.io.DataOutput;
71 import java.io.IOException;
72 import java.io.InvalidObjectException;
73 import java.io.ObjectStreamException;
74 import java.io.Serializable;
75 import java.time.Clock;
76 import java.time.DateTimeException;
77 import java.time.LocalDate;
78 import java.time.Month;
79 import java.time.ZoneId;
80 import java.time.format.DateTimeFormatter;
81 import java.time.format.DateTimeFormatterBuilder;
82 import java.time.format.DateTimeParseException;
83 import java.time.format.SignStyle;
84 import java.util.Objects;
85
86 /**
87 * A year in the ISO-8601 calendar system, such as {@code 2007}.
88 * <p>
89 * {@code Year} is an immutable date-time object that represents a year.
90 * Any field that can be derived from a year can be obtained.
91 * <p>
92 * <b>Note that years in the ISO chronology only align with years in the
93 * Gregorian-Julian system for modern years. Parts of Russia did not switch to the
94 * modern Gregorian/ISO rules until 1920.
95 * As such, historical years must be treated with caution.</b>
96 * <p>
97 * This class does not store or represent a month, day, time or time-zone.
98 * For example, the value "2007" can be stored in a {@code Year}.
99 * <p>
100 * Years represented by this class follow the ISO-8601 standard and use
101 * the proleptic numbering system. Year 1 is preceded by year 0, then by year -1.
102 * <p>
103 * The ISO-8601 calendar system is the modern civil calendar system used today
104 * in most of the world. It is equivalent to the proleptic Gregorian calendar
105 * system, in which today's rules for leap years are applied for all time.
106 * For most applications written today, the ISO-8601 rules are entirely suitable.
107 * However, any application that makes use of historical dates, and requires them
108 * to be accurate will find the ISO-8601 approach unsuitable.
109 *
110 * <h3>Specification for implementors</h3>
111 * This class is immutable and thread-safe.
112 *
113 * @since 1.8
114 */
115 public final class Year
116 implements Temporal, TemporalAdjuster, Comparable<Year>, Serializable {
117
118 /**
119 * The minimum supported year, '-999,999,999'.
120 */
121 public static final int MIN_VALUE = -999_999_999;
122 /**
123 * The maximum supported year, '+999,999,999'.
124 */
125 public static final int MAX_VALUE = 999_999_999;
126
127 /**
128 * Serialization version.
129 */
130 private static final long serialVersionUID = -23038383694477807L;
131 /**
132 * Parser.
133 */
134 private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder()
135 .appendValue(YEAR, 4, 10, SignStyle.EXCEEDS_PAD)
136 .toFormatter();
137
138 /**
139 * The year being represented.
140 */
141 private final int year;
142
143 //-----------------------------------------------------------------------
144 /**
145 * Obtains the current year from the system clock in the default time-zone.
146 * <p>
147 * This will query the {@link java.time.Clock#systemDefaultZone() system clock} in the default
148 * time-zone to obtain the current year.
149 * <p>
150 * Using this method will prevent the ability to use an alternate clock for testing
151 * because the clock is hard-coded.
152 *
153 * @return the current year using the system clock and default time-zone, not null
154 */
155 public static Year now() {
156 return now(Clock.systemDefaultZone());
157 }
158
159 /**
160 * Obtains the current year from the system clock in the specified time-zone.
161 * <p>
162 * This will query the {@link Clock#system(java.time.ZoneId) system clock} to obtain the current year.
163 * Specifying the time-zone avoids dependence on the default time-zone.
164 * <p>
165 * Using this method will prevent the ability to use an alternate clock for testing
166 * because the clock is hard-coded.
167 *
168 * @param zone the zone ID to use, not null
169 * @return the current year using the system clock, not null
170 */
171 public static Year now(ZoneId zone) {
172 return now(Clock.system(zone));
173 }
174
175 /**
176 * Obtains the current year from the specified clock.
177 * <p>
178 * This will query the specified clock to obtain the current year.
179 * Using this method allows the use of an alternate clock for testing.
180 * The alternate clock may be introduced using {@link Clock dependency injection}.
181 *
182 * @param clock the clock to use, not null
183 * @return the current year, not null
184 */
185 public static Year now(Clock clock) {
186 final LocalDate now = LocalDate.now(clock); // called once
187 return Year.of(now.getYear());
188 }
189
190 //-----------------------------------------------------------------------
191 /**
192 * Obtains an instance of {@code Year}.
193 * <p>
194 * This method accepts a year value from the proleptic ISO calendar system.
195 * <p>
196 * The year 2AD/CE is represented by 2.<br>
197 * The year 1AD/CE is represented by 1.<br>
198 * The year 1BC/BCE is represented by 0.<br>
199 * The year 2BC/BCE is represented by -1.<br>
200 *
201 * @param isoYear the ISO proleptic year to represent, from {@code MIN_VALUE} to {@code MAX_VALUE}
202 * @return the year, not null
203 * @throws DateTimeException if the field is invalid
204 */
205 public static Year of(int isoYear) {
206 YEAR.checkValidValue(isoYear);
207 return new Year(isoYear);
208 }
209
210 //-----------------------------------------------------------------------
211 /**
212 * Obtains an instance of {@code Year} from a temporal object.
213 * <p>
214 * A {@code TemporalAccessor} represents some form of date and time information.
215 * This factory converts the arbitrary temporal object to an instance of {@code Year}.
216 * <p>
217 * The conversion extracts the {@link ChronoField#YEAR year} field.
218 * The extraction is only permitted if the temporal object has an ISO
219 * chronology, or can be converted to a {@code LocalDate}.
220 * <p>
221 * This method matches the signature of the functional interface {@link TemporalQuery}
222 * allowing it to be used in queries via method reference, {@code Year::from}.
223 *
224 * @param temporal the temporal object to convert, not null
225 * @return the year, not null
226 * @throws DateTimeException if unable to convert to a {@code Year}
227 */
228 public static Year from(TemporalAccessor temporal) {
229 if (temporal instanceof Year) {
230 return (Year) temporal;
231 }
232 try {
233 if (ISOChrono.INSTANCE.equals(Chrono.from(temporal)) == false) {
234 temporal = LocalDate.from(temporal);
235 }
236 return of(temporal.get(YEAR));
237 } catch (DateTimeException ex) {
238 throw new DateTimeException("Unable to obtain Year from TemporalAccessor: " + temporal.getClass(), ex);
239 }
240 }
241
242 //-----------------------------------------------------------------------
243 /**
244 * Obtains an instance of {@code Year} from a text string such as {@code 2007}.
245 * <p>
246 * The string must represent a valid year.
247 * Years outside the range 0000 to 9999 must be prefixed by the plus or minus symbol.
248 *
249 * @param text the text to parse such as "2007", not null
250 * @return the parsed year, not null
251 * @throws DateTimeParseException if the text cannot be parsed
252 */
253 public static Year parse(CharSequence text) {
254 return parse(text, PARSER);
255 }
256
257 /**
258 * Obtains an instance of {@code Year} from a text string using a specific formatter.
259 * <p>
260 * The text is parsed using the formatter, returning a year.
261 *
262 * @param text the text to parse, not null
263 * @param formatter the formatter to use, not null
264 * @return the parsed year, not null
265 * @throws DateTimeParseException if the text cannot be parsed
266 */
267 public static Year parse(CharSequence text, DateTimeFormatter formatter) {
268 Objects.requireNonNull(formatter, "formatter");
269 return formatter.parse(text, Year::from);
270 }
271
272 //-------------------------------------------------------------------------
273 /**
274 * Checks if the year is a leap year, according to the ISO proleptic
275 * calendar system rules.
276 * <p>
277 * This method applies the current rules for leap years across the whole time-line.
278 * In general, a year is a leap year if it is divisible by four without
279 * remainder. However, years divisible by 100, are not leap years, with
280 * the exception of years divisible by 400 which are.
281 * <p>
282 * For example, 1904 is a leap year it is divisible by 4.
283 * 1900 was not a leap year as it is divisible by 100, however 2000 was a
284 * leap year as it is divisible by 400.
285 * <p>
286 * The calculation is proleptic - applying the same rules into the far future and far past.
287 * This is historically inaccurate, but is correct for the ISO-8601 standard.
288 *
289 * @param year the year to check
290 * @return true if the year is leap, false otherwise
291 */
292 public static boolean isLeap(long year) {
293 return ((year & 3) == 0) && ((year % 100) != 0 || (year % 400) == 0);
294 }
295
296 //-----------------------------------------------------------------------
297 /**
298 * Constructor.
299 *
300 * @param year the year to represent
301 */
302 private Year(int year) {
303 this.year = year;
304 }
305
306 //-----------------------------------------------------------------------
307 /**
308 * Gets the year value.
309 * <p>
310 * The year returned by this method is proleptic as per {@code get(YEAR)}.
311 *
312 * @return the year, {@code MIN_VALUE} to {@code MAX_VALUE}
313 */
314 public int getValue() {
315 return year;
316 }
317
318 //-----------------------------------------------------------------------
319 /**
320 * Checks if the specified field is supported.
321 * <p>
322 * This checks if this year can be queried for the specified field.
323 * If false, then calling the {@link #range(TemporalField) range} and
324 * {@link #get(TemporalField) get} methods will throw an exception.
325 * <p>
326 * If the field is a {@link ChronoField} then the query is implemented here.
327 * The {@link #isSupported(TemporalField) supported fields} will return valid
328 * values based on this date-time.
329 * The supported fields are:
330 * <ul>
331 * <li>{@code YEAR_OF_ERA}
332 * <li>{@code YEAR}
333 * <li>{@code ERA}
334 * </ul>
335 * All other {@code ChronoField} instances will return false.
336 * <p>
337 * If the field is not a {@code ChronoField}, then the result of this method
338 * is obtained by invoking {@code TemporalField.doIsSupported(TemporalAccessor)}
339 * passing {@code this} as the argument.
340 * Whether the field is supported is determined by the field.
341 *
342 * @param field the field to check, null returns false
343 * @return true if the field is supported on this year, false if not
344 */
345 @Override
346 public boolean isSupported(TemporalField field) {
347 if (field instanceof ChronoField) {
348 return field == YEAR || field == YEAR_OF_ERA || field == ERA;
349 }
350 return field != null && field.doIsSupported(this);
351 }
352
353 /**
354 * Gets the range of valid values for the specified field.
355 * <p>
356 * The range object expresses the minimum and maximum valid values for a field.
357 * This year is used to enhance the accuracy of the returned range.
358 * If it is not possible to return the range, because the field is not supported
359 * or for some other reason, an exception is thrown.
360 * <p>
361 * If the field is a {@link ChronoField} then the query is implemented here.
362 * The {@link #isSupported(TemporalField) supported fields} will return
363 * appropriate range instances.
364 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
365 * <p>
366 * If the field is not a {@code ChronoField}, then the result of this method
367 * is obtained by invoking {@code TemporalField.doRange(TemporalAccessor)}
368 * passing {@code this} as the argument.
369 * Whether the range can be obtained is determined by the field.
370 *
371 * @param field the field to query the range for, not null
372 * @return the range of valid values for the field, not null
373 * @throws DateTimeException if the range for the field cannot be obtained
374 */
375 @Override
376 public ValueRange range(TemporalField field) {
377 if (field == YEAR_OF_ERA) {
378 return (year <= 0 ? ValueRange.of(1, MAX_VALUE + 1) : ValueRange.of(1, MAX_VALUE));
379 }
380 return Temporal.super.range(field);
381 }
382
383 /**
384 * Gets the value of the specified field from this year as an {@code int}.
385 * <p>
386 * This queries this year for the value for the specified field.
387 * The returned value will always be within the valid range of values for the field.
388 * If it is not possible to return the value, because the field is not supported
389 * or for some other reason, an exception is thrown.
390 * <p>
391 * If the field is a {@link ChronoField} then the query is implemented here.
392 * The {@link #isSupported(TemporalField) supported fields} will return valid
393 * values based on this year.
394 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
395 * <p>
396 * If the field is not a {@code ChronoField}, then the result of this method
397 * is obtained by invoking {@code TemporalField.doGet(TemporalAccessor)}
398 * passing {@code this} as the argument. Whether the value can be obtained,
399 * and what the value represents, is determined by the field.
400 *
401 * @param field the field to get, not null
402 * @return the value for the field
403 * @throws DateTimeException if a value for the field cannot be obtained
404 * @throws ArithmeticException if numeric overflow occurs
405 */
406 @Override // override for Javadoc
407 public int get(TemporalField field) {
408 return range(field).checkValidIntValue(getLong(field), field);
409 }
410
411 /**
412 * Gets the value of the specified field from this year as a {@code long}.
413 * <p>
414 * This queries this year for the value for the specified field.
415 * If it is not possible to return the value, because the field is not supported
416 * or for some other reason, an exception is thrown.
417 * <p>
418 * If the field is a {@link ChronoField} then the query is implemented here.
419 * The {@link #isSupported(TemporalField) supported fields} will return valid
420 * values based on this year.
421 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
422 * <p>
423 * If the field is not a {@code ChronoField}, then the result of this method
424 * is obtained by invoking {@code TemporalField.doGet(TemporalAccessor)}
425 * passing {@code this} as the argument. Whether the value can be obtained,
426 * and what the value represents, is determined by the field.
427 *
428 * @param field the field to get, not null
429 * @return the value for the field
430 * @throws DateTimeException if a value for the field cannot be obtained
431 * @throws ArithmeticException if numeric overflow occurs
432 */
433 @Override
434 public long getLong(TemporalField field) {
435 if (field instanceof ChronoField) {
436 switch ((ChronoField) field) {
437 case YEAR_OF_ERA: return (year < 1 ? 1 - year : year);
438 case YEAR: return year;
439 case ERA: return (year < 1 ? 0 : 1);
440 }
441 throw new DateTimeException("Unsupported field: " + field.getName());
442 }
443 return field.doGet(this);
444 }
445
446 //-----------------------------------------------------------------------
447 /**
448 * Checks if the year is a leap year, according to the ISO proleptic
449 * calendar system rules.
450 * <p>
451 * This method applies the current rules for leap years across the whole time-line.
452 * In general, a year is a leap year if it is divisible by four without
453 * remainder. However, years divisible by 100, are not leap years, with
454 * the exception of years divisible by 400 which are.
455 * <p>
456 * For example, 1904 is a leap year it is divisible by 4.
457 * 1900 was not a leap year as it is divisible by 100, however 2000 was a
458 * leap year as it is divisible by 400.
459 * <p>
460 * The calculation is proleptic - applying the same rules into the far future and far past.
461 * This is historically inaccurate, but is correct for the ISO-8601 standard.
462 *
463 * @return true if the year is leap, false otherwise
464 */
465 public boolean isLeap() {
466 return Year.isLeap(year);
467 }
468
469 /**
470 * Checks if the month-day is valid for this year.
471 * <p>
472 * This method checks whether this year and the input month and day form
473 * a valid date.
474 *
475 * @param monthDay the month-day to validate, null returns false
476 * @return true if the month and day are valid for this year
477 */
478 public boolean isValidMonthDay(MonthDay monthDay) {
479 return monthDay != null && monthDay.isValidYear(year);
480 }
481
482 /**
483 * Gets the length of this year in days.
484 *
485 * @return the length of this year in days, 365 or 366
486 */
487 public int length() {
488 return isLeap() ? 366 : 365;
489 }
490
491 //-----------------------------------------------------------------------
492 /**
493 * Returns an adjusted copy of this year.
494 * <p>
495 * This returns a new {@code Year}, based on this one, with the year adjusted.
496 * The adjustment takes place using the specified adjuster strategy object.
497 * Read the documentation of the adjuster to understand what adjustment will be made.
498 * <p>
499 * The result of this method is obtained by invoking the
500 * {@link TemporalAdjuster#adjustInto(Temporal)} method on the
501 * specified adjuster passing {@code this} as the argument.
502 * <p>
503 * This instance is immutable and unaffected by this method call.
504 *
505 * @param adjuster the adjuster to use, not null
506 * @return a {@code Year} based on {@code this} with the adjustment made, not null
507 * @throws DateTimeException if the adjustment cannot be made
508 * @throws ArithmeticException if numeric overflow occurs
509 */
510 @Override
511 public Year with(TemporalAdjuster adjuster) {
512 return (Year) adjuster.adjustInto(this);
513 }
514
515 /**
516 * Returns a copy of this year with the specified field set to a new value.
517 * <p>
518 * This returns a new {@code Year}, based on this one, with the value
519 * for the specified field changed.
520 * If it is not possible to set the value, because the field is not supported or for
521 * some other reason, an exception is thrown.
522 * <p>
523 * If the field is a {@link ChronoField} then the adjustment is implemented here.
524 * The supported fields behave as follows:
525 * <ul>
526 * <li>{@code YEAR_OF_ERA} -
527 * Returns a {@code Year} with the specified year-of-era
528 * The era will be unchanged.
529 * <li>{@code YEAR} -
530 * Returns a {@code Year} with the specified year.
531 * This completely replaces the date and is equivalent to {@link #of(int)}.
532 * <li>{@code ERA} -
533 * Returns a {@code Year} with the specified era.
534 * The year-of-era will be unchanged.
535 * </ul>
536 * <p>
537 * In all cases, if the new value is outside the valid range of values for the field
538 * then a {@code DateTimeException} will be thrown.
539 * <p>
540 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
541 * <p>
542 * If the field is not a {@code ChronoField}, then the result of this method
543 * is obtained by invoking {@code TemporalField.doWith(Temporal, long)}
544 * passing {@code this} as the argument. In this case, the field determines
545 * whether and how to adjust the instant.
546 * <p>
547 * This instance is immutable and unaffected by this method call.
548 *
549 * @param field the field to set in the result, not null
550 * @param newValue the new value of the field in the result
551 * @return a {@code Year} based on {@code this} with the specified field set, not null
552 * @throws DateTimeException if the field cannot be set
553 * @throws ArithmeticException if numeric overflow occurs
554 */
555 @Override
556 public Year with(TemporalField field, long newValue) {
557 if (field instanceof ChronoField) {
558 ChronoField f = (ChronoField) field;
559 f.checkValidValue(newValue);
560 switch (f) {
561 case YEAR_OF_ERA: return Year.of((int) (year < 1 ? 1 - newValue : newValue));
562 case YEAR: return Year.of((int) newValue);
563 case ERA: return (getLong(ERA) == newValue ? this : Year.of(1 - year));
564 }
565 throw new DateTimeException("Unsupported field: " + field.getName());
566 }
567 return field.doWith(this, newValue);
568 }
569
570 //-----------------------------------------------------------------------
571 /**
572 * Returns a copy of this year with the specified period added.
573 * <p>
574 * This method returns a new year based on this year with the specified period added.
575 * The adder is typically {@link java.time.Period} but may be any other type implementing
576 * the {@link TemporalAdder} interface.
577 * The calculation is delegated to the specified adjuster, which typically calls
578 * back to {@link #plus(long, TemporalUnit)}.
579 * <p>
580 * This instance is immutable and unaffected by this method call.
581 *
582 * @param adder the adder to use, not null
583 * @return a {@code Year} based on this year with the addition made, not null
584 * @throws DateTimeException if the addition cannot be made
585 * @throws ArithmeticException if numeric overflow occurs
586 */
587 @Override
588 public Year plus(TemporalAdder adder) {
589 return (Year) adder.addTo(this);
590 }
591
592 /**
593 * {@inheritDoc}
594 * @throws DateTimeException {@inheritDoc}
595 * @throws ArithmeticException {@inheritDoc}
596 */
597 @Override
598 public Year plus(long amountToAdd, TemporalUnit unit) {
599 if (unit instanceof ChronoUnit) {
600 switch ((ChronoUnit) unit) {
601 case YEARS: return plusYears(amountToAdd);
602 case DECADES: return plusYears(Math.multiplyExact(amountToAdd, 10));
603 case CENTURIES: return plusYears(Math.multiplyExact(amountToAdd, 100));
604 case MILLENNIA: return plusYears(Math.multiplyExact(amountToAdd, 1000));
605 case ERAS: return with(ERA, Math.addExact(getLong(ERA), amountToAdd));
606 }
607 throw new DateTimeException("Unsupported unit: " + unit.getName());
608 }
609 return unit.doPlus(this, amountToAdd);
610 }
611
612 /**
613 * Returns a copy of this year with the specified number of years added.
614 * <p>
615 * This instance is immutable and unaffected by this method call.
616 *
617 * @param yearsToAdd the years to add, may be negative
618 * @return a {@code Year} based on this year with the period added, not null
619 * @throws DateTimeException if the result exceeds the supported year range
620 */
621 public Year plusYears(long yearsToAdd) {
622 if (yearsToAdd == 0) {
623 return this;
624 }
625 return of(YEAR.checkValidIntValue(year + yearsToAdd)); // overflow safe
626 }
627
628 //-----------------------------------------------------------------------
629 /**
630 * Returns a copy of this year with the specified period subtracted.
631 * <p>
632 * This method returns a new year based on this year with the specified period subtracted.
633 * The subtractor is typically {@link java.time.Period} but may be any other type implementing
634 * the {@link TemporalSubtractor} interface.
635 * The calculation is delegated to the specified adjuster, which typically calls
636 * back to {@link #minus(long, TemporalUnit)}.
637 * <p>
638 * This instance is immutable and unaffected by this method call.
639 *
640 * @param subtractor the subtractor to use, not null
641 * @return a {@code Year} based on this year with the subtraction made, not null
642 * @throws DateTimeException if the subtraction cannot be made
643 * @throws ArithmeticException if numeric overflow occurs
644 */
645 @Override
646 public Year minus(TemporalSubtractor subtractor) {
647 return (Year) subtractor.subtractFrom(this);
648 }
649
650 /**
651 * {@inheritDoc}
652 * @throws DateTimeException {@inheritDoc}
653 * @throws ArithmeticException {@inheritDoc}
654 */
655 @Override
656 public Year minus(long amountToSubtract, TemporalUnit unit) {
657 return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
658 }
659
660 /**
661 * Returns a copy of this year with the specified number of years subtracted.
662 * <p>
663 * This instance is immutable and unaffected by this method call.
664 *
665 * @param yearsToSubtract the years to subtract, may be negative
666 * @return a {@code Year} based on this year with the period subtracted, not null
667 * @throws DateTimeException if the result exceeds the supported year range
668 */
669 public Year minusYears(long yearsToSubtract) {
670 return (yearsToSubtract == Long.MIN_VALUE ? plusYears(Long.MAX_VALUE).plusYears(1) : plusYears(-yearsToSubtract));
671 }
672
673 //-----------------------------------------------------------------------
674 /**
675 * Queries this year using the specified query.
676 * <p>
677 * This queries this year using the specified query strategy object.
678 * The {@code TemporalQuery} object defines the logic to be used to
679 * obtain the result. Read the documentation of the query to understand
680 * what the result of this method will be.
681 * <p>
682 * The result of this method is obtained by invoking the
683 * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
684 * specified query passing {@code this} as the argument.
685 *
686 * @param <R> the type of the result
687 * @param query the query to invoke, not null
688 * @return the query result, null may be returned (defined by the query)
689 * @throws DateTimeException if unable to query (defined by the query)
690 * @throws ArithmeticException if numeric overflow occurs (defined by the query)
691 */
692 @SuppressWarnings("unchecked")
693 @Override
694 public <R> R query(TemporalQuery<R> query) {
695 if (query == Queries.chrono()) {
696 return (R) ISOChrono.INSTANCE;
697 } else if (query == Queries.precision()) {
698 return (R) YEARS;
699 }
700 return Temporal.super.query(query);
701 }
702
703 /**
704 * Adjusts the specified temporal object to have this year.
705 * <p>
706 * This returns a temporal object of the same observable type as the input
707 * with the year changed to be the same as this.
708 * <p>
709 * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
710 * passing {@link ChronoField#YEAR} as the field.
711 * If the specified temporal object does not use the ISO calendar system then
712 * a {@code DateTimeException} is thrown.
713 * <p>
714 * In most cases, it is clearer to reverse the calling pattern by using
715 * {@link Temporal#with(TemporalAdjuster)}:
716 * <pre>
717 * // these two lines are equivalent, but the second approach is recommended
718 * temporal = thisYear.adjustInto(temporal);
719 * temporal = temporal.with(thisYear);
720 * </pre>
721 * <p>
722 * This instance is immutable and unaffected by this method call.
723 *
724 * @param temporal the target object to be adjusted, not null
725 * @return the adjusted object, not null
726 * @throws DateTimeException if unable to make the adjustment
727 * @throws ArithmeticException if numeric overflow occurs
728 */
729 @Override
730 public Temporal adjustInto(Temporal temporal) {
731 if (Chrono.from(temporal).equals(ISOChrono.INSTANCE) == false) {
732 throw new DateTimeException("Adjustment only supported on ISO date-time");
733 }
734 return temporal.with(YEAR, year);
735 }
736
737 /**
738 * Calculates the period between this year and another year in
739 * terms of the specified unit.
740 * <p>
741 * This calculates the period between two years in terms of a single unit.
742 * The start and end points are {@code this} and the specified year.
743 * The result will be negative if the end is before the start.
744 * The {@code Temporal} passed to this method must be a {@code Year}.
745 * For example, the period in decades between two year can be calculated
746 * using {@code startYear.periodUntil(endYear, DECADES)}.
747 * <p>
748 * The calculation returns a whole number, representing the number of
749 * complete units between the two years.
750 * For example, the period in decades between 2012 and 2031
751 * will only be one decade as it is one year short of two decades.
752 * <p>
753 * This method operates in association with {@link TemporalUnit#between}.
754 * The result of this method is a {@code long} representing the amount of
755 * the specified unit. By contrast, the result of {@code between} is an
756 * object that can be used directly in addition/subtraction:
757 * <pre>
758 * long period = start.periodUntil(end, YEARS); // this method
759 * dateTime.plus(YEARS.between(start, end)); // use in plus/minus
760 * </pre>
761 * <p>
762 * The calculation is implemented in this method for {@link ChronoUnit}.
763 * The units {@code YEARS}, {@code DECADES}, {@code CENTURIES},
764 * {@code MILLENNIA} and {@code ERAS} are supported.
765 * Other {@code ChronoUnit} values will throw an exception.
766 * <p>
767 * If the unit is not a {@code ChronoUnit}, then the result of this method
768 * is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)}
769 * passing {@code this} as the first argument and the input temporal as
770 * the second argument.
771 * <p>
772 * This instance is immutable and unaffected by this method call.
773 *
774 * @param endYear the end year, which must be a {@code Year}, not null
775 * @param unit the unit to measure the period in, not null
776 * @return the amount of the period between this year and the end year
777 * @throws DateTimeException if the period cannot be calculated
778 * @throws ArithmeticException if numeric overflow occurs
779 */
780 @Override
781 public long periodUntil(Temporal endYear, TemporalUnit unit) {
782 if (endYear instanceof Year == false) {
783 Objects.requireNonNull(endYear, "endYear");
784 throw new DateTimeException("Unable to calculate period between objects of two different types");
785 }
786 Year end = (Year) endYear;
787 if (unit instanceof ChronoUnit) {
788 long yearsUntil = ((long) end.year) - year; // no overflow
789 switch ((ChronoUnit) unit) {
790 case YEARS: return yearsUntil;
791 case DECADES: return yearsUntil / 10;
792 case CENTURIES: return yearsUntil / 100;
793 case MILLENNIA: return yearsUntil / 1000;
794 case ERAS: return end.getLong(ERA) - getLong(ERA);
795 }
796 throw new DateTimeException("Unsupported unit: " + unit.getName());
797 }
798 return unit.between(this, endYear).getAmount();
799 }
800
801 //-----------------------------------------------------------------------
802 /**
803 * Returns a date formed from this year at the specified day-of-year.
804 * <p>
805 * This combines this year and the specified day-of-year to form a {@code LocalDate}.
806 * The day-of-year value 366 is only valid in a leap year.
807 * <p>
808 * This instance is immutable and unaffected by this method call.
809 *
810 * @param dayOfYear the day-of-year to use, not null
811 * @return the local date formed from this year and the specified date of year, not null
812 * @throws DateTimeException if the day of year is 366 and this is not a leap year
813 */
814 public LocalDate atDay(int dayOfYear) {
815 return LocalDate.ofYearDay(year, dayOfYear);
816 }
817
818 /**
819 * Returns a year-month formed from this year at the specified month.
820 * <p>
821 * This combines this year and the specified month to form a {@code YearMonth}.
822 * All possible combinations of year and month are valid.
823 * <p>
824 * This method can be used as part of a chain to produce a date:
825 * <pre>
826 * LocalDate date = year.atMonth(month).atDay(day);
827 * </pre>
828 * <p>
829 * This instance is immutable and unaffected by this method call.
830 *
831 * @param month the month-of-year to use, not null
832 * @return the year-month formed from this year and the specified month, not null
833 */
834 public YearMonth atMonth(Month month) {
835 return YearMonth.of(year, month);
836 }
837
838 /**
839 * Returns a year-month formed from this year at the specified month.
840 * <p>
841 * This combines this year and the specified month to form a {@code YearMonth}.
842 * All possible combinations of year and month are valid.
843 * <p>
844 * This method can be used as part of a chain to produce a date:
845 * <pre>
846 * LocalDate date = year.atMonth(month).atDay(day);
847 * </pre>
848 * <p>
849 * This instance is immutable and unaffected by this method call.
850 *
851 * @param month the month-of-year to use, from 1 (January) to 12 (December)
852 * @return the year-month formed from this year and the specified month, not null
853 */
854 public YearMonth atMonth(int month) {
855 return YearMonth.of(year, month);
856 }
857
858 /**
859 * Returns a date formed from this year at the specified month-day.
860 * <p>
861 * This combines this year and the specified month-day to form a {@code LocalDate}.
862 * The month-day value of February 29th is only valid in a leap year.
863 * <p>
864 * This instance is immutable and unaffected by this method call.
865 *
866 * @param monthDay the month-day to use, not null
867 * @return the local date formed from this year and the specified month-day, not null
868 * @throws DateTimeException if the month-day is February 29th and this is not a leap year
869 */
870 public LocalDate atMonthDay(MonthDay monthDay) {
871 return LocalDate.of(year, monthDay.getMonth(), monthDay.getDayOfMonth());
872 }
873
874 //-----------------------------------------------------------------------
875 /**
876 * Compares this year to another year.
877 * <p>
878 * The comparison is based on the value of the year.
879 * It is "consistent with equals", as defined by {@link Comparable}.
880 *
881 * @param other the other year to compare to, not null
882 * @return the comparator value, negative if less, positive if greater
883 */
884 public int compareTo(Year other) {
885 return year - other.year;
886 }
887
888 /**
889 * Is this year after the specified year.
890 *
891 * @param other the other year to compare to, not null
892 * @return true if this is after the specified year
893 */
894 public boolean isAfter(Year other) {
895 return year > other.year;
896 }
897
898 /**
899 * Is this year before the specified year.
900 *
901 * @param other the other year to compare to, not null
902 * @return true if this point is before the specified year
903 */
904 public boolean isBefore(Year other) {
905 return year < other.year;
906 }
907
908 //-----------------------------------------------------------------------
909 /**
910 * Checks if this year is equal to another year.
911 * <p>
912 * The comparison is based on the time-line position of the years.
913 *
914 * @param obj the object to check, null returns false
915 * @return true if this is equal to the other year
916 */
917 @Override
918 public boolean equals(Object obj) {
919 if (this == obj) {
920 return true;
921 }
922 if (obj instanceof Year) {
923 return year == ((Year) obj).year;
924 }
925 return false;
926 }
927
928 /**
929 * A hash code for this year.
930 *
931 * @return a suitable hash code
932 */
933 @Override
934 public int hashCode() {
935 return year;
936 }
937
938 //-----------------------------------------------------------------------
939 /**
940 * Outputs this year as a {@code String}.
941 *
942 * @return a string representation of this year, not null
943 */
944 @Override
945 public String toString() {
946 return Integer.toString(year);
947 }
948
949 /**
950 * Outputs this year as a {@code String} using the formatter.
951 * <p>
952 * This year will be passed to the formatter
953 * {@link DateTimeFormatter#print(TemporalAccessor) print method}.
954 *
955 * @param formatter the formatter to use, not null
956 * @return the formatted year string, not null
957 * @throws DateTimeException if an error occurs during printing
958 */
959 public String toString(DateTimeFormatter formatter) {
960 Objects.requireNonNull(formatter, "formatter");
961 return formatter.print(this);
962 }
963
964 //-----------------------------------------------------------------------
965 /**
966 * Writes the object using a
967 * <a href="../../../serialized-form.html#java.time.temporal.Ser">dedicated serialized form</a>.
968 * <pre>
969 * out.writeByte(4); // identifies this as a Year
970 * out.writeInt(year);
971 * </pre>
972 *
973 * @return the instance of {@code Ser}, not null
974 */
975 private Object writeReplace() {
976 return new Ser(Ser.YEAR_TYPE, this);
977 }
978
979 /**
980 * Defend against malicious streams.
981 * @return never
982 * @throws InvalidObjectException always
983 */
984 private Object readResolve() throws ObjectStreamException {
985 throw new InvalidObjectException("Deserialization via serialization delegate");
986 }
987
988 void writeExternal(DataOutput out) throws IOException {
989 out.writeInt(year);
990 }
991
992 static Year readExternal(DataInput in) throws IOException {
993 return Year.of(in.readInt());
994 }
995
996 }