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.EPOCH_MONTH;
65 import static java.time.temporal.ChronoField.ERA;
66 import static java.time.temporal.ChronoField.MONTH_OF_YEAR;
67 import static java.time.temporal.ChronoField.YEAR;
68 import static java.time.temporal.ChronoField.YEAR_OF_ERA;
69 import static java.time.temporal.ChronoUnit.MONTHS;
70
71 import java.io.DataInput;
72 import java.io.DataOutput;
73 import java.io.IOException;
74 import java.io.InvalidObjectException;
75 import java.io.ObjectStreamException;
76 import java.io.Serializable;
77 import java.time.Clock;
78 import java.time.DateTimeException;
79 import java.time.LocalDate;
80 import java.time.Month;
81 import java.time.ZoneId;
82 import java.time.format.DateTimeFormatter;
83 import java.time.format.DateTimeFormatterBuilder;
84 import java.time.format.DateTimeParseException;
85 import java.time.format.SignStyle;
86 import java.util.Objects;
87
88 /**
89 * A year-month in the ISO-8601 calendar system, such as {@code 2007-12}.
90 * <p>
91 * {@code YearMonth} is an immutable date-time object that represents the combination
92 * of a year and month. Any field that can be derived from a year and month, such as
93 * quarter-of-year, can be obtained.
94 * <p>
95 * This class does not store or represent a day, time or time-zone.
96 * For example, the value "October 2007" can be stored in a {@code YearMonth}.
97 * <p>
98 * The ISO-8601 calendar system is the modern civil calendar system used today
99 * in most of the world. It is equivalent to the proleptic Gregorian calendar
100 * system, in which today's rules for leap years are applied for all time.
101 * For most applications written today, the ISO-8601 rules are entirely suitable.
102 * However, any application that makes use of historical dates, and requires them
103 * to be accurate will find the ISO-8601 approach unsuitable.
104 *
105 * <h3>Specification for implementors</h3>
106 * This class is immutable and thread-safe.
107 *
108 * @since 1.8
109 */
110 public final class YearMonth
111 implements Temporal, TemporalAdjuster, Comparable<YearMonth>, Serializable {
112
113 /**
114 * Serialization version.
115 */
116 private static final long serialVersionUID = 4183400860270640070L;
117 /**
118 * Parser.
119 */
120 private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder()
121 .appendValue(YEAR, 4, 10, SignStyle.EXCEEDS_PAD)
122 .appendLiteral('-')
123 .appendValue(MONTH_OF_YEAR, 2)
124 .toFormatter();
125
126 /**
127 * The year.
128 */
129 private final int year;
130 /**
131 * The month-of-year, not null.
132 */
133 private final int month;
134
135 //-----------------------------------------------------------------------
136 /**
137 * Obtains the current year-month from the system clock in the default time-zone.
138 * <p>
139 * This will query the {@link java.time.Clock#systemDefaultZone() system clock} in the default
140 * time-zone to obtain the current year-month.
141 * The zone and offset will be set based on the time-zone in the clock.
142 * <p>
143 * Using this method will prevent the ability to use an alternate clock for testing
144 * because the clock is hard-coded.
145 *
146 * @return the current year-month using the system clock and default time-zone, not null
147 */
148 public static YearMonth now() {
149 return now(Clock.systemDefaultZone());
150 }
151
152 /**
153 * Obtains the current year-month from the system clock in the specified time-zone.
154 * <p>
155 * This will query the {@link Clock#system(java.time.ZoneId) system clock} to obtain the current year-month.
156 * Specifying the time-zone avoids dependence on the default time-zone.
157 * <p>
158 * Using this method will prevent the ability to use an alternate clock for testing
159 * because the clock is hard-coded.
160 *
161 * @param zone the zone ID to use, not null
162 * @return the current year-month using the system clock, not null
163 */
164 public static YearMonth now(ZoneId zone) {
165 return now(Clock.system(zone));
166 }
167
168 /**
169 * Obtains the current year-month from the specified clock.
170 * <p>
171 * This will query the specified clock to obtain the current year-month.
172 * Using this method allows the use of an alternate clock for testing.
173 * The alternate clock may be introduced using {@link Clock dependency injection}.
174 *
175 * @param clock the clock to use, not null
176 * @return the current year-month, not null
177 */
178 public static YearMonth now(Clock clock) {
179 final LocalDate now = LocalDate.now(clock); // called once
180 return YearMonth.of(now.getYear(), now.getMonth());
181 }
182
183 //-----------------------------------------------------------------------
184 /**
185 * Obtains an instance of {@code YearMonth} from a year and month.
186 *
187 * @param year the year to represent, from MIN_YEAR to MAX_YEAR
188 * @param month the month-of-year to represent, not null
189 * @return the year-month, not null
190 * @throws DateTimeException if the year value is invalid
191 */
192 public static YearMonth of(int year, Month month) {
193 Objects.requireNonNull(month, "month");
194 return of(year, month.getValue());
195 }
196
197 /**
198 * Obtains an instance of {@code YearMonth} from a year and month.
199 *
200 * @param year the year to represent, from MIN_YEAR to MAX_YEAR
201 * @param month the month-of-year to represent, from 1 (January) to 12 (December)
202 * @return the year-month, not null
203 * @throws DateTimeException if either field value is invalid
204 */
205 public static YearMonth of(int year, int month) {
206 YEAR.checkValidValue(year);
207 MONTH_OF_YEAR.checkValidValue(month);
208 return new YearMonth(year, month);
209 }
210
211 //-----------------------------------------------------------------------
212 /**
213 * Obtains an instance of {@code YearMonth} from a temporal object.
214 * <p>
215 * A {@code TemporalAccessor} represents some form of date and time information.
216 * This factory converts the arbitrary temporal object to an instance of {@code YearMonth}.
217 * <p>
218 * The conversion extracts the {@link ChronoField#YEAR YEAR} and
219 * {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} fields.
220 * The extraction is only permitted if the temporal object has an ISO
221 * chronology, or can be converted to a {@code LocalDate}.
222 * <p>
223 * This method matches the signature of the functional interface {@link TemporalQuery}
224 * allowing it to be used in queries via method reference, {@code YearMonth::from}.
225 *
226 * @param temporal the temporal object to convert, not null
227 * @return the year-month, not null
228 * @throws DateTimeException if unable to convert to a {@code YearMonth}
229 */
230 public static YearMonth from(TemporalAccessor temporal) {
231 if (temporal instanceof YearMonth) {
232 return (YearMonth) temporal;
233 }
234 try {
235 if (ISOChrono.INSTANCE.equals(Chrono.from(temporal)) == false) {
236 temporal = LocalDate.from(temporal);
237 }
238 return of(temporal.get(YEAR), temporal.get(MONTH_OF_YEAR));
239 } catch (DateTimeException ex) {
240 throw new DateTimeException("Unable to obtain YearMonth from TemporalAccessor: " + temporal.getClass(), ex);
241 }
242 }
243
244 //-----------------------------------------------------------------------
245 /**
246 * Obtains an instance of {@code YearMonth} from a text string such as {@code 2007-12}.
247 * <p>
248 * The string must represent a valid year-month.
249 * The format must be {@code yyyy-MM}.
250 * Years outside the range 0000 to 9999 must be prefixed by the plus or minus symbol.
251 *
252 * @param text the text to parse such as "2007-12", not null
253 * @return the parsed year-month, not null
254 * @throws DateTimeParseException if the text cannot be parsed
255 */
256 public static YearMonth parse(CharSequence text) {
257 return parse(text, PARSER);
258 }
259
260 /**
261 * Obtains an instance of {@code YearMonth} from a text string using a specific formatter.
262 * <p>
263 * The text is parsed using the formatter, returning a year-month.
264 *
265 * @param text the text to parse, not null
266 * @param formatter the formatter to use, not null
267 * @return the parsed year-month, not null
268 * @throws DateTimeParseException if the text cannot be parsed
269 */
270 public static YearMonth parse(CharSequence text, DateTimeFormatter formatter) {
271 Objects.requireNonNull(formatter, "formatter");
272 return formatter.parse(text, YearMonth::from);
273 }
274
275 //-----------------------------------------------------------------------
276 /**
277 * Constructor.
278 *
279 * @param year the year to represent, validated from MIN_YEAR to MAX_YEAR
280 * @param month the month-of-year to represent, validated from 1 (January) to 12 (December)
281 */
282 private YearMonth(int year, int month) {
283 this.year = year;
284 this.month = month;
285 }
286
287 /**
288 * Returns a copy of this year-month with the new year and month, checking
289 * to see if a new object is in fact required.
290 *
291 * @param newYear the year to represent, validated from MIN_YEAR to MAX_YEAR
292 * @param newMonth the month-of-year to represent, validated not null
293 * @return the year-month, not null
294 */
295 private YearMonth with(int newYear, int newMonth) {
296 if (year == newYear && month == newMonth) {
297 return this;
298 }
299 return new YearMonth(newYear, newMonth);
300 }
301
302 //-----------------------------------------------------------------------
303 /**
304 * Checks if the specified field is supported.
305 * <p>
306 * This checks if this year-month can be queried for the specified field.
307 * If false, then calling the {@link #range(TemporalField) range} and
308 * {@link #get(TemporalField) get} methods will throw an exception.
309 * <p>
310 * If the field is a {@link ChronoField} then the query is implemented here.
311 * The {@link #isSupported(TemporalField) supported fields} will return valid
312 * values based on this date-time.
313 * The supported fields are:
314 * <ul>
315 * <li>{@code MONTH_OF_YEAR}
316 * <li>{@code EPOCH_MONTH}
317 * <li>{@code YEAR_OF_ERA}
318 * <li>{@code YEAR}
319 * <li>{@code ERA}
320 * </ul>
321 * All other {@code ChronoField} instances will return false.
322 * <p>
323 * If the field is not a {@code ChronoField}, then the result of this method
324 * is obtained by invoking {@code TemporalField.doIsSupported(TemporalAccessor)}
325 * passing {@code this} as the argument.
326 * Whether the field is supported is determined by the field.
327 *
328 * @param field the field to check, null returns false
329 * @return true if the field is supported on this year-month, false if not
330 */
331 @Override
332 public boolean isSupported(TemporalField field) {
333 if (field instanceof ChronoField) {
334 return field == YEAR || field == MONTH_OF_YEAR ||
335 field == EPOCH_MONTH || field == YEAR_OF_ERA || field == ERA;
336 }
337 return field != null && field.doIsSupported(this);
338 }
339
340 /**
341 * Gets the range of valid values for the specified field.
342 * <p>
343 * The range object expresses the minimum and maximum valid values for a field.
344 * This year-month is used to enhance the accuracy of the returned range.
345 * If it is not possible to return the range, because the field is not supported
346 * or for some other reason, an exception is thrown.
347 * <p>
348 * If the field is a {@link ChronoField} then the query is implemented here.
349 * The {@link #isSupported(TemporalField) supported fields} will return
350 * appropriate range instances.
351 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
352 * <p>
353 * If the field is not a {@code ChronoField}, then the result of this method
354 * is obtained by invoking {@code TemporalField.doRange(TemporalAccessor)}
355 * passing {@code this} as the argument.
356 * Whether the range can be obtained is determined by the field.
357 *
358 * @param field the field to query the range for, not null
359 * @return the range of valid values for the field, not null
360 * @throws DateTimeException if the range for the field cannot be obtained
361 */
362 @Override
363 public ValueRange range(TemporalField field) {
364 if (field == YEAR_OF_ERA) {
365 return (getYear() <= 0 ? ValueRange.of(1, Year.MAX_VALUE + 1) : ValueRange.of(1, Year.MAX_VALUE));
366 }
367 return Temporal.super.range(field);
368 }
369
370 /**
371 * Gets the value of the specified field from this year-month as an {@code int}.
372 * <p>
373 * This queries this year-month for the value for the specified field.
374 * The returned value will always be within the valid range of values for the field.
375 * If it is not possible to return the value, because the field is not supported
376 * or for some other reason, an exception is thrown.
377 * <p>
378 * If the field is a {@link ChronoField} then the query is implemented here.
379 * The {@link #isSupported(TemporalField) supported fields} will return valid
380 * values based on this year-month, except {@code EPOCH_MONTH} which is too
381 * large to fit in an {@code int} and throw a {@code DateTimeException}.
382 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
383 * <p>
384 * If the field is not a {@code ChronoField}, then the result of this method
385 * is obtained by invoking {@code TemporalField.doGet(TemporalAccessor)}
386 * passing {@code this} as the argument. Whether the value can be obtained,
387 * and what the value represents, is determined by the field.
388 *
389 * @param field the field to get, not null
390 * @return the value for the field
391 * @throws DateTimeException if a value for the field cannot be obtained
392 * @throws ArithmeticException if numeric overflow occurs
393 */
394 @Override // override for Javadoc
395 public int get(TemporalField field) {
396 return range(field).checkValidIntValue(getLong(field), field);
397 }
398
399 /**
400 * Gets the value of the specified field from this year-month as a {@code long}.
401 * <p>
402 * This queries this year-month for the value for the specified field.
403 * If it is not possible to return the value, because the field is not supported
404 * or for some other reason, an exception is thrown.
405 * <p>
406 * If the field is a {@link ChronoField} then the query is implemented here.
407 * The {@link #isSupported(TemporalField) supported fields} will return valid
408 * values based on this year-month.
409 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
410 * <p>
411 * If the field is not a {@code ChronoField}, then the result of this method
412 * is obtained by invoking {@code TemporalField.doGet(TemporalAccessor)}
413 * passing {@code this} as the argument. Whether the value can be obtained,
414 * and what the value represents, is determined by the field.
415 *
416 * @param field the field to get, not null
417 * @return the value for the field
418 * @throws DateTimeException if a value for the field cannot be obtained
419 * @throws ArithmeticException if numeric overflow occurs
420 */
421 @Override
422 public long getLong(TemporalField field) {
423 if (field instanceof ChronoField) {
424 switch ((ChronoField) field) {
425 case MONTH_OF_YEAR: return month;
426 case EPOCH_MONTH: return getEpochMonth();
427 case YEAR_OF_ERA: return (year < 1 ? 1 - year : year);
428 case YEAR: return year;
429 case ERA: return (year < 1 ? 0 : 1);
430 }
431 throw new DateTimeException("Unsupported field: " + field.getName());
432 }
433 return field.doGet(this);
434 }
435
436 private long getEpochMonth() {
437 return ((year - 1970) * 12L) + (month - 1);
438 }
439
440 //-----------------------------------------------------------------------
441 /**
442 * Gets the year field.
443 * <p>
444 * This method returns the primitive {@code int} value for the year.
445 * <p>
446 * The year returned by this method is proleptic as per {@code get(YEAR)}.
447 *
448 * @return the year, from MIN_YEAR to MAX_YEAR
449 */
450 public int getYear() {
451 return year;
452 }
453
454 /**
455 * Gets the month-of-year field using the {@code Month} enum.
456 * <p>
457 * This method returns the enum {@link Month} for the month.
458 * This avoids confusion as to what {@code int} values mean.
459 * If you need access to the primitive {@code int} value then the enum
460 * provides the {@link Month#getValue() int value}.
461 *
462 * @return the month-of-year, not null
463 */
464 public Month getMonth() {
465 return Month.of(month);
466 }
467
468 //-----------------------------------------------------------------------
469 /**
470 * Checks if the year is a leap year, according to the ISO proleptic
471 * calendar system rules.
472 * <p>
473 * This method applies the current rules for leap years across the whole time-line.
474 * In general, a year is a leap year if it is divisible by four without
475 * remainder. However, years divisible by 100, are not leap years, with
476 * the exception of years divisible by 400 which are.
477 * <p>
478 * For example, 1904 is a leap year it is divisible by 4.
479 * 1900 was not a leap year as it is divisible by 100, however 2000 was a
480 * leap year as it is divisible by 400.
481 * <p>
482 * The calculation is proleptic - applying the same rules into the far future and far past.
483 * This is historically inaccurate, but is correct for the ISO-8601 standard.
484 *
485 * @return true if the year is leap, false otherwise
486 */
487 public boolean isLeapYear() {
488 return ISOChrono.INSTANCE.isLeapYear(year);
489 }
490
491 /**
492 * Checks if the day-of-month is valid for this year-month.
493 * <p>
494 * This method checks whether this year and month and the input day form
495 * a valid date.
496 *
497 * @param dayOfMonth the day-of-month to validate, from 1 to 31, invalid value returns false
498 * @return true if the day is valid for this year-month
499 */
500 public boolean isValidDay(int dayOfMonth) {
501 return dayOfMonth >= 1 && dayOfMonth <= lengthOfMonth();
502 }
503
504 /**
505 * Returns the length of the month, taking account of the year.
506 * <p>
507 * This returns the length of the month in days.
508 * For example, a date in January would return 31.
509 *
510 * @return the length of the month in days, from 28 to 31
511 */
512 public int lengthOfMonth() {
513 return getMonth().length(isLeapYear());
514 }
515
516 /**
517 * Returns the length of the year.
518 * <p>
519 * This returns the length of the year in days, either 365 or 366.
520 *
521 * @return 366 if the year is leap, 365 otherwise
522 */
523 public int lengthOfYear() {
524 return (isLeapYear() ? 366 : 365);
525 }
526
527 //-----------------------------------------------------------------------
528 /**
529 * Returns an adjusted copy of this year-month.
530 * <p>
531 * This returns a new {@code YearMonth}, based on this one, with the year-month adjusted.
532 * The adjustment takes place using the specified adjuster strategy object.
533 * Read the documentation of the adjuster to understand what adjustment will be made.
534 * <p>
535 * A simple adjuster might simply set the one of the fields, such as the year field.
536 * A more complex adjuster might set the year-month to the next month that
537 * Halley's comet will pass the Earth.
538 * <p>
539 * The result of this method is obtained by invoking the
540 * {@link TemporalAdjuster#adjustInto(Temporal)} method on the
541 * specified adjuster passing {@code this} as the argument.
542 * <p>
543 * This instance is immutable and unaffected by this method call.
544 *
545 * @param adjuster the adjuster to use, not null
546 * @return a {@code YearMonth} based on {@code this} with the adjustment made, not null
547 * @throws DateTimeException if the adjustment cannot be made
548 * @throws ArithmeticException if numeric overflow occurs
549 */
550 @Override
551 public YearMonth with(TemporalAdjuster adjuster) {
552 return (YearMonth) adjuster.adjustInto(this);
553 }
554
555 /**
556 * Returns a copy of this year-month with the specified field set to a new value.
557 * <p>
558 * This returns a new {@code YearMonth}, based on this one, with the value
559 * for the specified field changed.
560 * This can be used to change any supported field, such as the year or month.
561 * If it is not possible to set the value, because the field is not supported or for
562 * some other reason, an exception is thrown.
563 * <p>
564 * If the field is a {@link ChronoField} then the adjustment is implemented here.
565 * The supported fields behave as follows:
566 * <ul>
567 * <li>{@code MONTH_OF_YEAR} -
568 * Returns a {@code YearMonth} with the specified month-of-year.
569 * The year will be unchanged.
570 * <li>{@code EPOCH_MONTH} -
571 * Returns a {@code YearMonth} with the specified epoch-month.
572 * This completely replaces the year and month of this object.
573 * <li>{@code YEAR_OF_ERA} -
574 * Returns a {@code YearMonth} with the specified year-of-era
575 * The month and era will be unchanged.
576 * <li>{@code YEAR} -
577 * Returns a {@code YearMonth} with the specified year.
578 * The month will be unchanged.
579 * <li>{@code ERA} -
580 * Returns a {@code YearMonth} with the specified era.
581 * The month and year-of-era will be unchanged.
582 * </ul>
583 * <p>
584 * In all cases, if the new value is outside the valid range of values for the field
585 * then a {@code DateTimeException} will be thrown.
586 * <p>
587 * All other {@code ChronoField} instances will throw a {@code DateTimeException}.
588 * <p>
589 * If the field is not a {@code ChronoField}, then the result of this method
590 * is obtained by invoking {@code TemporalField.doWith(Temporal, long)}
591 * passing {@code this} as the argument. In this case, the field determines
592 * whether and how to adjust the instant.
593 * <p>
594 * This instance is immutable and unaffected by this method call.
595 *
596 * @param field the field to set in the result, not null
597 * @param newValue the new value of the field in the result
598 * @return a {@code YearMonth} based on {@code this} with the specified field set, not null
599 * @throws DateTimeException if the field cannot be set
600 * @throws ArithmeticException if numeric overflow occurs
601 */
602 @Override
603 public YearMonth with(TemporalField field, long newValue) {
604 if (field instanceof ChronoField) {
605 ChronoField f = (ChronoField) field;
606 f.checkValidValue(newValue);
607 switch (f) {
608 case MONTH_OF_YEAR: return withMonth((int) newValue);
609 case EPOCH_MONTH: return plusMonths(newValue - getLong(EPOCH_MONTH));
610 case YEAR_OF_ERA: return withYear((int) (year < 1 ? 1 - newValue : newValue));
611 case YEAR: return withYear((int) newValue);
612 case ERA: return (getLong(ERA) == newValue ? this : withYear(1 - year));
613 }
614 throw new DateTimeException("Unsupported field: " + field.getName());
615 }
616 return field.doWith(this, newValue);
617 }
618
619 //-----------------------------------------------------------------------
620 /**
621 * Returns a copy of this {@code YearMonth} with the year altered.
622 * <p>
623 * This instance is immutable and unaffected by this method call.
624 *
625 * @param year the year to set in the returned year-month, from MIN_YEAR to MAX_YEAR
626 * @return a {@code YearMonth} based on this year-month with the requested year, not null
627 * @throws DateTimeException if the year value is invalid
628 */
629 public YearMonth withYear(int year) {
630 YEAR.checkValidValue(year);
631 return with(year, month);
632 }
633
634 /**
635 * Returns a copy of this {@code YearMonth} with the month-of-year altered.
636 * <p>
637 * This instance is immutable and unaffected by this method call.
638 *
639 * @param month the month-of-year to set in the returned year-month, from 1 (January) to 12 (December)
640 * @return a {@code YearMonth} based on this year-month with the requested month, not null
641 * @throws DateTimeException if the month-of-year value is invalid
642 */
643 public YearMonth withMonth(int month) {
644 MONTH_OF_YEAR.checkValidValue(month);
645 return with(year, month);
646 }
647
648 //-----------------------------------------------------------------------
649 /**
650 * Returns a copy of this year-month with the specified period added.
651 * <p>
652 * This method returns a new year-month based on this year-month with the specified period added.
653 * The adder is typically {@link java.time.Period} but may be any other type implementing
654 * the {@link TemporalAdder} interface.
655 * The calculation is delegated to the specified adjuster, which typically calls
656 * back to {@link #plus(long, TemporalUnit)}.
657 * <p>
658 * This instance is immutable and unaffected by this method call.
659 *
660 * @param adder the adder to use, not null
661 * @return a {@code YearMonth} based on this year-month with the addition made, not null
662 * @throws DateTimeException if the addition cannot be made
663 * @throws ArithmeticException if numeric overflow occurs
664 */
665 @Override
666 public YearMonth plus(TemporalAdder adder) {
667 return (YearMonth) adder.addTo(this);
668 }
669
670 /**
671 * {@inheritDoc}
672 * @throws DateTimeException {@inheritDoc}
673 * @throws ArithmeticException {@inheritDoc}
674 */
675 @Override
676 public YearMonth plus(long amountToAdd, TemporalUnit unit) {
677 if (unit instanceof ChronoUnit) {
678 switch ((ChronoUnit) unit) {
679 case MONTHS: return plusMonths(amountToAdd);
680 case YEARS: return plusYears(amountToAdd);
681 case DECADES: return plusYears(Math.multiplyExact(amountToAdd, 10));
682 case CENTURIES: return plusYears(Math.multiplyExact(amountToAdd, 100));
683 case MILLENNIA: return plusYears(Math.multiplyExact(amountToAdd, 1000));
684 case ERAS: return with(ERA, Math.addExact(getLong(ERA), amountToAdd));
685 }
686 throw new DateTimeException("Unsupported unit: " + unit.getName());
687 }
688 return unit.doPlus(this, amountToAdd);
689 }
690
691 /**
692 * Returns a copy of this year-month with the specified period in years added.
693 * <p>
694 * This instance is immutable and unaffected by this method call.
695 *
696 * @param yearsToAdd the years to add, may be negative
697 * @return a {@code YearMonth} based on this year-month with the years added, not null
698 * @throws DateTimeException if the result exceeds the supported range
699 */
700 public YearMonth plusYears(long yearsToAdd) {
701 if (yearsToAdd == 0) {
702 return this;
703 }
704 int newYear = YEAR.checkValidIntValue(year + yearsToAdd); // safe overflow
705 return with(newYear, month);
706 }
707
708 /**
709 * Returns a copy of this year-month with the specified period in months added.
710 * <p>
711 * This instance is immutable and unaffected by this method call.
712 *
713 * @param monthsToAdd the months to add, may be negative
714 * @return a {@code YearMonth} based on this year-month with the months added, not null
715 * @throws DateTimeException if the result exceeds the supported range
716 */
717 public YearMonth plusMonths(long monthsToAdd) {
718 if (monthsToAdd == 0) {
719 return this;
720 }
721 long monthCount = year * 12L + (month - 1);
722 long calcMonths = monthCount + monthsToAdd; // safe overflow
723 int newYear = YEAR.checkValidIntValue(Math.floorDiv(calcMonths, 12));
724 int newMonth = (int)Math.floorMod(calcMonths, 12) + 1;
725 return with(newYear, newMonth);
726 }
727
728 //-----------------------------------------------------------------------
729 /**
730 * Returns a copy of this year-month with the specified period subtracted.
731 * <p>
732 * This method returns a new year-month based on this year-month with the specified period subtracted.
733 * The subtractor is typically {@link java.time.Period} but may be any other type implementing
734 * the {@link TemporalSubtractor} interface.
735 * The calculation is delegated to the specified adjuster, which typically calls
736 * back to {@link #minus(long, TemporalUnit)}.
737 * <p>
738 * This instance is immutable and unaffected by this method call.
739 *
740 * @param subtractor the subtractor to use, not null
741 * @return a {@code YearMonth} based on this year-month with the subtraction made, not null
742 * @throws DateTimeException if the subtraction cannot be made
743 * @throws ArithmeticException if numeric overflow occurs
744 */
745 @Override
746 public YearMonth minus(TemporalSubtractor subtractor) {
747 return (YearMonth) subtractor.subtractFrom(this);
748 }
749
750 /**
751 * {@inheritDoc}
752 * @throws DateTimeException {@inheritDoc}
753 * @throws ArithmeticException {@inheritDoc}
754 */
755 @Override
756 public YearMonth minus(long amountToSubtract, TemporalUnit unit) {
757 return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
758 }
759
760 /**
761 * Returns a copy of this year-month with the specified period in years subtracted.
762 * <p>
763 * This instance is immutable and unaffected by this method call.
764 *
765 * @param yearsToSubtract the years to subtract, may be negative
766 * @return a {@code YearMonth} based on this year-month with the years subtracted, not null
767 * @throws DateTimeException if the result exceeds the supported range
768 */
769 public YearMonth minusYears(long yearsToSubtract) {
770 return (yearsToSubtract == Long.MIN_VALUE ? plusYears(Long.MAX_VALUE).plusYears(1) : plusYears(-yearsToSubtract));
771 }
772
773 /**
774 * Returns a copy of this year-month with the specified period in months subtracted.
775 * <p>
776 * This instance is immutable and unaffected by this method call.
777 *
778 * @param monthsToSubtract the months to subtract, may be negative
779 * @return a {@code YearMonth} based on this year-month with the months subtracted, not null
780 * @throws DateTimeException if the result exceeds the supported range
781 */
782 public YearMonth minusMonths(long monthsToSubtract) {
783 return (monthsToSubtract == Long.MIN_VALUE ? plusMonths(Long.MAX_VALUE).plusMonths(1) : plusMonths(-monthsToSubtract));
784 }
785
786 //-----------------------------------------------------------------------
787 /**
788 * Queries this year-month using the specified query.
789 * <p>
790 * This queries this year-month using the specified query strategy object.
791 * The {@code TemporalQuery} object defines the logic to be used to
792 * obtain the result. Read the documentation of the query to understand
793 * what the result of this method will be.
794 * <p>
795 * The result of this method is obtained by invoking the
796 * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
797 * specified query passing {@code this} as the argument.
798 *
799 * @param <R> the type of the result
800 * @param query the query to invoke, not null
801 * @return the query result, null may be returned (defined by the query)
802 * @throws DateTimeException if unable to query (defined by the query)
803 * @throws ArithmeticException if numeric overflow occurs (defined by the query)
804 */
805 @SuppressWarnings("unchecked")
806 @Override
807 public <R> R query(TemporalQuery<R> query) {
808 if (query == Queries.chrono()) {
809 return (R) ISOChrono.INSTANCE;
810 } else if (query == Queries.precision()) {
811 return (R) MONTHS;
812 }
813 return Temporal.super.query(query);
814 }
815
816 /**
817 * Adjusts the specified temporal object to have this year-month.
818 * <p>
819 * This returns a temporal object of the same observable type as the input
820 * with the year and month changed to be the same as this.
821 * <p>
822 * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
823 * passing {@link ChronoField#EPOCH_MONTH} as the field.
824 * If the specified temporal object does not use the ISO calendar system then
825 * a {@code DateTimeException} is thrown.
826 * <p>
827 * In most cases, it is clearer to reverse the calling pattern by using
828 * {@link Temporal#with(TemporalAdjuster)}:
829 * <pre>
830 * // these two lines are equivalent, but the second approach is recommended
831 * temporal = thisYearMonth.adjustInto(temporal);
832 * temporal = temporal.with(thisYearMonth);
833 * </pre>
834 * <p>
835 * This instance is immutable and unaffected by this method call.
836 *
837 * @param temporal the target object to be adjusted, not null
838 * @return the adjusted object, not null
839 * @throws DateTimeException if unable to make the adjustment
840 * @throws ArithmeticException if numeric overflow occurs
841 */
842 @Override
843 public Temporal adjustInto(Temporal temporal) {
844 if (Chrono.from(temporal).equals(ISOChrono.INSTANCE) == false) {
845 throw new DateTimeException("Adjustment only supported on ISO date-time");
846 }
847 return temporal.with(EPOCH_MONTH, getEpochMonth());
848 }
849
850 /**
851 * Calculates the period between this year-month and another year-month in
852 * terms of the specified unit.
853 * <p>
854 * This calculates the period between two year-months in terms of a single unit.
855 * The start and end points are {@code this} and the specified year-month.
856 * The result will be negative if the end is before the start.
857 * The {@code Temporal} passed to this method must be a {@code YearMonth}.
858 * For example, the period in years between two year-months can be calculated
859 * using {@code startYearMonth.periodUntil(endYearMonth, YEARS)}.
860 * <p>
861 * The calculation returns a whole number, representing the number of
862 * complete units between the two year-months.
863 * For example, the period in decades between 2012-06 and 2032-05
864 * will only be one decade as it is one month short of two decades.
865 * <p>
866 * This method operates in association with {@link TemporalUnit#between}.
867 * The result of this method is a {@code long} representing the amount of
868 * the specified unit. By contrast, the result of {@code between} is an
869 * object that can be used directly in addition/subtraction:
870 * <pre>
871 * long period = start.periodUntil(end, YEARS); // this method
872 * dateTime.plus(YEARS.between(start, end)); // use in plus/minus
873 * </pre>
874 * <p>
875 * The calculation is implemented in this method for {@link ChronoUnit}.
876 * The units {@code MONTHS}, {@code YEARS}, {@code DECADES},
877 * {@code CENTURIES}, {@code MILLENNIA} and {@code ERAS} are supported.
878 * Other {@code ChronoUnit} values will throw an exception.
879 * <p>
880 * If the unit is not a {@code ChronoUnit}, then the result of this method
881 * is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)}
882 * passing {@code this} as the first argument and the input temporal as
883 * the second argument.
884 * <p>
885 * This instance is immutable and unaffected by this method call.
886 *
887 * @param endYearMonth the end year-month, which must be a {@code YearMonth}, not null
888 * @param unit the unit to measure the period in, not null
889 * @return the amount of the period between this year-month and the end year-month
890 * @throws DateTimeException if the period cannot be calculated
891 * @throws ArithmeticException if numeric overflow occurs
892 */
893 @Override
894 public long periodUntil(Temporal endYearMonth, TemporalUnit unit) {
895 if (endYearMonth instanceof YearMonth == false) {
896 Objects.requireNonNull(endYearMonth, "endYearMonth");
897 throw new DateTimeException("Unable to calculate period between objects of two different types");
898 }
899 YearMonth end = (YearMonth) endYearMonth;
900 if (unit instanceof ChronoUnit) {
901 long monthsUntil = end.getEpochMonth() - getEpochMonth(); // no overflow
902 switch ((ChronoUnit) unit) {
903 case MONTHS: return monthsUntil;
904 case YEARS: return monthsUntil / 12;
905 case DECADES: return monthsUntil / 120;
906 case CENTURIES: return monthsUntil / 1200;
907 case MILLENNIA: return monthsUntil / 12000;
908 case ERAS: return end.getLong(ERA) - getLong(ERA);
909 }
910 throw new DateTimeException("Unsupported unit: " + unit.getName());
911 }
912 return unit.between(this, endYearMonth).getAmount();
913 }
914
915 //-----------------------------------------------------------------------
916 /**
917 * Returns a date formed from this year-month at the specified day-of-month.
918 * <p>
919 * This combines this year-month and the specified day-of-month to form a {@code LocalDate}.
920 * The day-of-month value must be valid for the year-month.
921 * <p>
922 * This method can be used as part of a chain to produce a date:
923 * <pre>
924 * LocalDate date = year.atMonth(month).atDay(day);
925 * </pre>
926 * <p>
927 * This instance is immutable and unaffected by this method call.
928 *
929 * @param dayOfMonth the day-of-month to use, from 1 to 31
930 * @return the date formed from this year-month and the specified day, not null
931 * @throws DateTimeException when the day is invalid for the year-month
932 * @see #isValidDay(int)
933 */
934 public LocalDate atDay(int dayOfMonth) {
935 return LocalDate.of(year, month, dayOfMonth);
936 }
937
938 //-----------------------------------------------------------------------
939 /**
940 * Compares this year-month to another year-month.
941 * <p>
942 * The comparison is based first on the value of the year, then on the value of the month.
943 * It is "consistent with equals", as defined by {@link Comparable}.
944 *
945 * @param other the other year-month to compare to, not null
946 * @return the comparator value, negative if less, positive if greater
947 */
948 @Override
949 public int compareTo(YearMonth other) {
950 int cmp = (year - other.year);
951 if (cmp == 0) {
952 cmp = (month - other.month);
953 }
954 return cmp;
955 }
956
957 /**
958 * Is this year-month after the specified year-month.
959 *
960 * @param other the other year-month to compare to, not null
961 * @return true if this is after the specified year-month
962 */
963 public boolean isAfter(YearMonth other) {
964 return compareTo(other) > 0;
965 }
966
967 /**
968 * Is this year-month before the specified year-month.
969 *
970 * @param other the other year-month to compare to, not null
971 * @return true if this point is before the specified year-month
972 */
973 public boolean isBefore(YearMonth other) {
974 return compareTo(other) < 0;
975 }
976
977 //-----------------------------------------------------------------------
978 /**
979 * Checks if this year-month is equal to another year-month.
980 * <p>
981 * The comparison is based on the time-line position of the year-months.
982 *
983 * @param obj the object to check, null returns false
984 * @return true if this is equal to the other year-month
985 */
986 @Override
987 public boolean equals(Object obj) {
988 if (this == obj) {
989 return true;
990 }
991 if (obj instanceof YearMonth) {
992 YearMonth other = (YearMonth) obj;
993 return year == other.year && month == other.month;
994 }
995 return false;
996 }
997
998 /**
999 * A hash code for this year-month.
1000 *
1001 * @return a suitable hash code
1002 */
1003 @Override
1004 public int hashCode() {
1005 return year ^ (month << 27);
1006 }
1007
1008 //-----------------------------------------------------------------------
1009 /**
1010 * Outputs this year-month as a {@code String}, such as {@code 2007-12}.
1011 * <p>
1012 * The output will be in the format {@code yyyy-MM}:
1013 *
1014 * @return a string representation of this year-month, not null
1015 */
1016 @Override
1017 public String toString() {
1018 int absYear = Math.abs(year);
1019 StringBuilder buf = new StringBuilder(9);
1020 if (absYear < 1000) {
1021 if (year < 0) {
1022 buf.append(year - 10000).deleteCharAt(1);
1023 } else {
1024 buf.append(year + 10000).deleteCharAt(0);
1025 }
1026 } else {
1027 buf.append(year);
1028 }
1029 return buf.append(month < 10 ? "-0" : "-")
1030 .append(month)
1031 .toString();
1032 }
1033
1034 /**
1035 * Outputs this year-month as a {@code String} using the formatter.
1036 * <p>
1037 * This year-month will be passed to the formatter
1038 * {@link DateTimeFormatter#print(TemporalAccessor) print method}.
1039 *
1040 * @param formatter the formatter to use, not null
1041 * @return the formatted year-month string, not null
1042 * @throws DateTimeException if an error occurs during printing
1043 */
1044 public String toString(DateTimeFormatter formatter) {
1045 Objects.requireNonNull(formatter, "formatter");
1046 return formatter.print(this);
1047 }
1048
1049 //-----------------------------------------------------------------------
1050 /**
1051 * Writes the object using a
1052 * <a href="../../../serialized-form.html#java.time.temporal.Ser">dedicated serialized form</a>.
1053 * <pre>
1054 * out.writeByte(5); // identifies this as a Year
1055 * out.writeInt(year);
1056 * out.writeByte(month);
1057 * </pre>
1058 *
1059 * @return the instance of {@code Ser}, not null
1060 */
1061 private Object writeReplace() {
1062 return new Ser(Ser.YEAR_MONTH_TYPE, this);
1063 }
1064
1065 /**
1066 * Defend against malicious streams.
1067 * @return never
1068 * @throws InvalidObjectException always
1069 */
1070 private Object readResolve() throws ObjectStreamException {
1071 throw new InvalidObjectException("Deserialization via serialization delegate");
1072 }
1073
1074 void writeExternal(DataOutput out) throws IOException {
1075 out.writeInt(year);
1076 out.writeByte(month);
1077 }
1078
1079 static YearMonth readExternal(DataInput in) throws IOException {
1080 int year = in.readInt();
1081 byte month = in.readByte();
1082 return YearMonth.of(year, month);
1083 }
1084
1085 }