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;
63
64 import static java.time.temporal.ChronoField.ERA;
65 import static java.time.temporal.ChronoField.MONTH_OF_YEAR;
66 import static java.time.temporal.ChronoField.PROLEPTIC_MONTH;
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.chrono.Chronology;
78 import java.time.chrono.IsoChronology;
79 import java.time.format.DateTimeFormatter;
80 import java.time.format.DateTimeFormatterBuilder;
81 import java.time.format.DateTimeParseException;
82 import java.time.format.SignStyle;
83 import java.time.temporal.ChronoField;
84 import java.time.temporal.ChronoUnit;
85 import java.time.temporal.Temporal;
86 import java.time.temporal.TemporalAccessor;
87 import java.time.temporal.TemporalAdjuster;
88 import java.time.temporal.TemporalAmount;
89 import java.time.temporal.TemporalField;
90 import java.time.temporal.TemporalQuery;
91 import java.time.temporal.TemporalUnit;
92 import java.time.temporal.UnsupportedTemporalTypeException;
93 import java.time.temporal.ValueRange;
94 import java.util.Objects;
95
96 /**
97 * A year-month in the ISO-8601 calendar system, such as {@code 2007-12}.
98 * <p>
99 * {@code YearMonth} is an immutable date-time object that represents the combination
100 * of a year and month. Any field that can be derived from a year and month, such as
101 * quarter-of-year, can be obtained.
102 * <p>
103 * This class does not store or represent a day, time or time-zone.
104 * For example, the value "October 2007" can be stored in a {@code YearMonth}.
105 * <p>
106 * The ISO-8601 calendar system is the modern civil calendar system used today
107 * in most of the world. It is equivalent to the proleptic Gregorian calendar
108 * system, in which today's rules for leap years are applied for all time.
109 * For most applications written today, the ISO-8601 rules are entirely suitable.
110 * However, any application that makes use of historical dates, and requires them
111 * to be accurate will find the ISO-8601 approach unsuitable.
112 *
113 * <h3>Specification for implementors</h3>
114 * This class is immutable and thread-safe.
115 *
116 * @since 1.8
117 */
118 public final class YearMonth
119 implements Temporal, TemporalAdjuster, Comparable<YearMonth>, Serializable {
120
121 /**
122 * Serialization version.
123 */
124 private static final long serialVersionUID = 4183400860270640070L;
125 /**
126 * Parser.
127 */
128 private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder()
129 .appendValue(YEAR, 4, 10, SignStyle.EXCEEDS_PAD)
130 .appendLiteral('-')
131 .appendValue(MONTH_OF_YEAR, 2)
132 .toFormatter();
133
134 /**
135 * The year.
136 */
137 private final int year;
138 /**
139 * The month-of-year, not null.
140 */
141 private final int month;
142
143 //-----------------------------------------------------------------------
144 /**
145 * Obtains the current year-month 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-month.
149 * The zone and offset will be set based on the time-zone in the clock.
150 * <p>
151 * Using this method will prevent the ability to use an alternate clock for testing
152 * because the clock is hard-coded.
153 *
154 * @return the current year-month using the system clock and default time-zone, not null
155 */
156 public static YearMonth now() {
157 return now(Clock.systemDefaultZone());
158 }
159
160 /**
161 * Obtains the current year-month from the system clock in the specified time-zone.
162 * <p>
163 * This will query the {@link Clock#system(java.time.ZoneId) system clock} to obtain the current year-month.
164 * Specifying the time-zone avoids dependence on the default time-zone.
165 * <p>
166 * Using this method will prevent the ability to use an alternate clock for testing
167 * because the clock is hard-coded.
168 *
169 * @param zone the zone ID to use, not null
170 * @return the current year-month using the system clock, not null
171 */
172 public static YearMonth now(ZoneId zone) {
173 return now(Clock.system(zone));
174 }
175
176 /**
177 * Obtains the current year-month from the specified clock.
178 * <p>
179 * This will query the specified clock to obtain the current year-month.
180 * Using this method allows the use of an alternate clock for testing.
181 * The alternate clock may be introduced using {@link Clock dependency injection}.
182 *
183 * @param clock the clock to use, not null
184 * @return the current year-month, not null
185 */
186 public static YearMonth now(Clock clock) {
187 final LocalDate now = LocalDate.now(clock); // called once
188 return YearMonth.of(now.getYear(), now.getMonth());
189 }
190
191 //-----------------------------------------------------------------------
192 /**
193 * Obtains an instance of {@code YearMonth} from a year and month.
194 *
195 * @param year the year to represent, from MIN_YEAR to MAX_YEAR
196 * @param month the month-of-year to represent, not null
197 * @return the year-month, not null
198 * @throws DateTimeException if the year value is invalid
199 */
200 public static YearMonth of(int year, Month month) {
201 Objects.requireNonNull(month, "month");
202 return of(year, month.getValue());
203 }
204
205 /**
206 * Obtains an instance of {@code YearMonth} from a year and month.
207 *
208 * @param year the year to represent, from MIN_YEAR to MAX_YEAR
209 * @param month the month-of-year to represent, from 1 (January) to 12 (December)
210 * @return the year-month, not null
211 * @throws DateTimeException if either field value is invalid
212 */
213 public static YearMonth of(int year, int month) {
214 YEAR.checkValidValue(year);
215 MONTH_OF_YEAR.checkValidValue(month);
216 return new YearMonth(year, month);
217 }
218
219 //-----------------------------------------------------------------------
220 /**
221 * Obtains an instance of {@code YearMonth} from a temporal object.
222 * <p>
223 * This obtains a year-month based on the specified temporal.
224 * A {@code TemporalAccessor} represents an arbitrary set of date and time information,
225 * which this factory converts to an instance of {@code YearMonth}.
226 * <p>
227 * The conversion extracts the {@link ChronoField#YEAR YEAR} and
228 * {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} fields.
229 * The extraction is only permitted if the temporal object has an ISO
230 * chronology, or can be converted to a {@code LocalDate}.
231 * <p>
232 * This method matches the signature of the functional interface {@link TemporalQuery}
233 * allowing it to be used in queries via method reference, {@code YearMonth::from}.
234 *
235 * @param temporal the temporal object to convert, not null
236 * @return the year-month, not null
237 * @throws DateTimeException if unable to convert to a {@code YearMonth}
238 */
239 public static YearMonth from(TemporalAccessor temporal) {
240 if (temporal instanceof YearMonth) {
241 return (YearMonth) temporal;
242 }
243 try {
244 if (IsoChronology.INSTANCE.equals(Chronology.from(temporal)) == false) {
245 temporal = LocalDate.from(temporal);
246 }
247 return of(temporal.get(YEAR), temporal.get(MONTH_OF_YEAR));
248 } catch (DateTimeException ex) {
249 throw new DateTimeException("Unable to obtain YearMonth from TemporalAccessor: " + temporal.getClass(), ex);
250 }
251 }
252
253 //-----------------------------------------------------------------------
254 /**
255 * Obtains an instance of {@code YearMonth} from a text string such as {@code 2007-12}.
256 * <p>
257 * The string must represent a valid year-month.
258 * The format must be {@code uuuu-MM}.
259 * Years outside the range 0000 to 9999 must be prefixed by the plus or minus symbol.
260 *
261 * @param text the text to parse such as "2007-12", not null
262 * @return the parsed year-month, not null
263 * @throws DateTimeParseException if the text cannot be parsed
264 */
265 public static YearMonth parse(CharSequence text) {
266 return parse(text, PARSER);
267 }
268
269 /**
270 * Obtains an instance of {@code YearMonth} from a text string using a specific formatter.
271 * <p>
272 * The text is parsed using the formatter, returning a year-month.
273 *
274 * @param text the text to parse, not null
275 * @param formatter the formatter to use, not null
276 * @return the parsed year-month, not null
277 * @throws DateTimeParseException if the text cannot be parsed
278 */
279 public static YearMonth parse(CharSequence text, DateTimeFormatter formatter) {
280 Objects.requireNonNull(formatter, "formatter");
281 return formatter.parse(text, YearMonth::from);
282 }
283
284 //-----------------------------------------------------------------------
285 /**
286 * Constructor.
287 *
288 * @param year the year to represent, validated from MIN_YEAR to MAX_YEAR
289 * @param month the month-of-year to represent, validated from 1 (January) to 12 (December)
290 */
291 private YearMonth(int year, int month) {
292 this.year = year;
293 this.month = month;
294 }
295
296 /**
297 * Returns a copy of this year-month with the new year and month, checking
298 * to see if a new object is in fact required.
299 *
300 * @param newYear the year to represent, validated from MIN_YEAR to MAX_YEAR
301 * @param newMonth the month-of-year to represent, validated not null
302 * @return the year-month, not null
303 */
304 private YearMonth with(int newYear, int newMonth) {
305 if (year == newYear && month == newMonth) {
306 return this;
307 }
308 return new YearMonth(newYear, newMonth);
309 }
310
311 //-----------------------------------------------------------------------
312 /**
313 * Checks if the specified field is supported.
314 * <p>
315 * This checks if this year-month can be queried for the specified field.
316 * If false, then calling the {@link #range(TemporalField) range} and
317 * {@link #get(TemporalField) get} methods will throw an exception.
318 * <p>
319 * If the field is a {@link ChronoField} then the query is implemented here.
320 * The supported fields are:
321 * <ul>
322 * <li>{@code MONTH_OF_YEAR}
323 * <li>{@code PROLEPTIC_MONTH}
324 * <li>{@code YEAR_OF_ERA}
325 * <li>{@code YEAR}
326 * <li>{@code ERA}
327 * </ul>
328 * All other {@code ChronoField} instances will return false.
329 * <p>
330 * If the field is not a {@code ChronoField}, then the result of this method
331 * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)}
332 * passing {@code this} as the argument.
333 * Whether the field is supported is determined by the field.
334 *
335 * @param field the field to check, null returns false
336 * @return true if the field is supported on this year-month, false if not
337 */
338 @Override
339 public boolean isSupported(TemporalField field) {
340 if (field instanceof ChronoField) {
341 return field == YEAR || field == MONTH_OF_YEAR ||
342 field == PROLEPTIC_MONTH || field == YEAR_OF_ERA || field == ERA;
343 }
344 return field != null && field.isSupportedBy(this);
345 }
346
347 /**
348 * Gets the range of valid values for the specified field.
349 * <p>
350 * The range object expresses the minimum and maximum valid values for a field.
351 * This year-month is used to enhance the accuracy of the returned range.
352 * If it is not possible to return the range, because the field is not supported
353 * or for some other reason, an exception is thrown.
354 * <p>
355 * If the field is a {@link ChronoField} then the query is implemented here.
356 * The {@link #isSupported(TemporalField) supported fields} will return
357 * appropriate range instances.
358 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
359 * <p>
360 * If the field is not a {@code ChronoField}, then the result of this method
361 * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)}
362 * passing {@code this} as the argument.
363 * Whether the range can be obtained is determined by the field.
364 *
365 * @param field the field to query the range for, not null
366 * @return the range of valid values for the field, not null
367 * @throws DateTimeException if the range for the field cannot be obtained
368 * @throws UnsupportedTemporalTypeException if the field is not supported
369 */
370 @Override
371 public ValueRange range(TemporalField field) {
372 if (field == YEAR_OF_ERA) {
373 return (getYear() <= 0 ? ValueRange.of(1, Year.MAX_VALUE + 1) : ValueRange.of(1, Year.MAX_VALUE));
374 }
375 return Temporal.super.range(field);
376 }
377
378 /**
379 * Gets the value of the specified field from this year-month as an {@code int}.
380 * <p>
381 * This queries this year-month for the value for the specified field.
382 * The returned value will always be within the valid range of values for the field.
383 * If it is not possible to return the value, because the field is not supported
384 * or for some other reason, an exception is thrown.
385 * <p>
386 * If the field is a {@link ChronoField} then the query is implemented here.
387 * The {@link #isSupported(TemporalField) supported fields} will return valid
388 * values based on this year-month, except {@code PROLEPTIC_MONTH} which is too
389 * large to fit in an {@code int} and throw a {@code DateTimeException}.
390 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
391 * <p>
392 * If the field is not a {@code ChronoField}, then the result of this method
393 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
394 * passing {@code this} as the argument. Whether the value can be obtained,
395 * and what the value represents, is determined by the field.
396 *
397 * @param field the field to get, not null
398 * @return the value for the field
399 * @throws DateTimeException if a value for the field cannot be obtained or
400 * the value is outside the range of valid values for the field
401 * @throws UnsupportedTemporalTypeException if the field is not supported or
402 * the range of values exceeds an {@code int}
403 * @throws ArithmeticException if numeric overflow occurs
404 */
405 @Override // override for Javadoc
406 public int get(TemporalField field) {
407 return range(field).checkValidIntValue(getLong(field), field);
408 }
409
410 /**
411 * Gets the value of the specified field from this year-month as a {@code long}.
412 * <p>
413 * This queries this year-month for the value for the specified field.
414 * If it is not possible to return the value, because the field is not supported
415 * or for some other reason, an exception is thrown.
416 * <p>
417 * If the field is a {@link ChronoField} then the query is implemented here.
418 * The {@link #isSupported(TemporalField) supported fields} will return valid
419 * values based on this year-month.
420 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
421 * <p>
422 * If the field is not a {@code ChronoField}, then the result of this method
423 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)}
424 * passing {@code this} as the argument. Whether the value can be obtained,
425 * and what the value represents, is determined by the field.
426 *
427 * @param field the field to get, not null
428 * @return the value for the field
429 * @throws DateTimeException if a value for the field cannot be obtained
430 * @throws UnsupportedTemporalTypeException if the field is not supported
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 MONTH_OF_YEAR: return month;
438 case PROLEPTIC_MONTH: return getProlepticMonth();
439 case YEAR_OF_ERA: return (year < 1 ? 1 - year : year);
440 case YEAR: return year;
441 case ERA: return (year < 1 ? 0 : 1);
442 }
443 throw new UnsupportedTemporalTypeException("Unsupported field: " + field.getName());
444 }
445 return field.getFrom(this);
446 }
447
448 private long getProlepticMonth() {
449 return (year * 12L + month - 1);
450 }
451
452 //-----------------------------------------------------------------------
453 /**
454 * Gets the year field.
455 * <p>
456 * This method returns the primitive {@code int} value for the year.
457 * <p>
458 * The year returned by this method is proleptic as per {@code get(YEAR)}.
459 *
460 * @return the year, from MIN_YEAR to MAX_YEAR
461 */
462 public int getYear() {
463 return year;
464 }
465
466 /**
467 * Gets the month-of-year field from 1 to 12.
468 * <p>
469 * This method returns the month as an {@code int} from 1 to 12.
470 * Application code is frequently clearer if the enum {@link Month}
471 * is used by calling {@link #getMonth()}.
472 *
473 * @return the month-of-year, from 1 to 12
474 * @see #getMonth()
475 */
476 public int getMonthValue() {
477 return month;
478 }
479
480 /**
481 * Gets the month-of-year field using the {@code Month} enum.
482 * <p>
483 * This method returns the enum {@link Month} for the month.
484 * This avoids confusion as to what {@code int} values mean.
485 * If you need access to the primitive {@code int} value then the enum
486 * provides the {@link Month#getValue() int value}.
487 *
488 * @return the month-of-year, not null
489 * @see #getMonthValue()
490 */
491 public Month getMonth() {
492 return Month.of(month);
493 }
494
495 //-----------------------------------------------------------------------
496 /**
497 * Checks if the year is a leap year, according to the ISO proleptic
498 * calendar system rules.
499 * <p>
500 * This method applies the current rules for leap years across the whole time-line.
501 * In general, a year is a leap year if it is divisible by four without
502 * remainder. However, years divisible by 100, are not leap years, with
503 * the exception of years divisible by 400 which are.
504 * <p>
505 * For example, 1904 is a leap year it is divisible by 4.
506 * 1900 was not a leap year as it is divisible by 100, however 2000 was a
507 * leap year as it is divisible by 400.
508 * <p>
509 * The calculation is proleptic - applying the same rules into the far future and far past.
510 * This is historically inaccurate, but is correct for the ISO-8601 standard.
511 *
512 * @return true if the year is leap, false otherwise
513 */
514 public boolean isLeapYear() {
515 return IsoChronology.INSTANCE.isLeapYear(year);
516 }
517
518 /**
519 * Checks if the day-of-month is valid for this year-month.
520 * <p>
521 * This method checks whether this year and month and the input day form
522 * a valid date.
523 *
524 * @param dayOfMonth the day-of-month to validate, from 1 to 31, invalid value returns false
525 * @return true if the day is valid for this year-month
526 */
527 public boolean isValidDay(int dayOfMonth) {
528 return dayOfMonth >= 1 && dayOfMonth <= lengthOfMonth();
529 }
530
531 /**
532 * Returns the length of the month, taking account of the year.
533 * <p>
534 * This returns the length of the month in days.
535 * For example, a date in January would return 31.
536 *
537 * @return the length of the month in days, from 28 to 31
538 */
539 public int lengthOfMonth() {
540 return getMonth().length(isLeapYear());
541 }
542
543 /**
544 * Returns the length of the year.
545 * <p>
546 * This returns the length of the year in days, either 365 or 366.
547 *
548 * @return 366 if the year is leap, 365 otherwise
549 */
550 public int lengthOfYear() {
551 return (isLeapYear() ? 366 : 365);
552 }
553
554 //-----------------------------------------------------------------------
555 /**
556 * Returns an adjusted copy of this year-month.
557 * <p>
558 * This returns a {@code YearMonth}, based on this one, with the year-month adjusted.
559 * The adjustment takes place using the specified adjuster strategy object.
560 * Read the documentation of the adjuster to understand what adjustment will be made.
561 * <p>
562 * A simple adjuster might simply set the one of the fields, such as the year field.
563 * A more complex adjuster might set the year-month to the next month that
564 * Halley's comet will pass the Earth.
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 YearMonth} 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 YearMonth with(TemporalAdjuster adjuster) {
579 return (YearMonth) adjuster.adjustInto(this);
580 }
581
582 /**
583 * Returns a copy of this year-month with the specified field set to a new value.
584 * <p>
585 * This returns a {@code YearMonth}, based on this one, with the value
586 * for the specified field changed.
587 * This can be used to change any supported field, such as the year or month.
588 * If it is not possible to set the value, because the field is not supported or for
589 * some other reason, an exception is thrown.
590 * <p>
591 * If the field is a {@link ChronoField} then the adjustment is implemented here.
592 * The supported fields behave as follows:
593 * <ul>
594 * <li>{@code MONTH_OF_YEAR} -
595 * Returns a {@code YearMonth} with the specified month-of-year.
596 * The year will be unchanged.
597 * <li>{@code PROLEPTIC_MONTH} -
598 * Returns a {@code YearMonth} with the specified proleptic-month.
599 * This completely replaces the year and month of this object.
600 * <li>{@code YEAR_OF_ERA} -
601 * Returns a {@code YearMonth} with the specified year-of-era
602 * The month and era will be unchanged.
603 * <li>{@code YEAR} -
604 * Returns a {@code YearMonth} with the specified year.
605 * The month will be unchanged.
606 * <li>{@code ERA} -
607 * Returns a {@code YearMonth} with the specified era.
608 * The month and year-of-era will be unchanged.
609 * </ul>
610 * <p>
611 * In all cases, if the new value is outside the valid range of values for the field
612 * then a {@code DateTimeException} will be thrown.
613 * <p>
614 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
615 * <p>
616 * If the field is not a {@code ChronoField}, then the result of this method
617 * is obtained by invoking {@code TemporalField.adjustInto(Temporal, long)}
618 * passing {@code this} as the argument. In this case, the field determines
619 * whether and how to adjust the instant.
620 * <p>
621 * This instance is immutable and unaffected by this method call.
622 *
623 * @param field the field to set in the result, not null
624 * @param newValue the new value of the field in the result
625 * @return a {@code YearMonth} based on {@code this} with the specified field set, not null
626 * @throws DateTimeException if the field cannot be set
627 * @throws UnsupportedTemporalTypeException if the field is not supported
628 * @throws ArithmeticException if numeric overflow occurs
629 */
630 @Override
631 public YearMonth with(TemporalField field, long newValue) {
632 if (field instanceof ChronoField) {
633 ChronoField f = (ChronoField) field;
634 f.checkValidValue(newValue);
635 switch (f) {
636 case MONTH_OF_YEAR: return withMonth((int) newValue);
637 case PROLEPTIC_MONTH: return plusMonths(newValue - getProlepticMonth());
638 case YEAR_OF_ERA: return withYear((int) (year < 1 ? 1 - newValue : newValue));
639 case YEAR: return withYear((int) newValue);
640 case ERA: return (getLong(ERA) == newValue ? this : withYear(1 - year));
641 }
642 throw new UnsupportedTemporalTypeException("Unsupported field: " + field.getName());
643 }
644 return field.adjustInto(this, newValue);
645 }
646
647 //-----------------------------------------------------------------------
648 /**
649 * Returns a copy of this {@code YearMonth} with the year altered.
650 * <p>
651 * This instance is immutable and unaffected by this method call.
652 *
653 * @param year the year to set in the returned year-month, from MIN_YEAR to MAX_YEAR
654 * @return a {@code YearMonth} based on this year-month with the requested year, not null
655 * @throws DateTimeException if the year value is invalid
656 */
657 public YearMonth withYear(int year) {
658 YEAR.checkValidValue(year);
659 return with(year, month);
660 }
661
662 /**
663 * Returns a copy of this {@code YearMonth} with the month-of-year altered.
664 * <p>
665 * This instance is immutable and unaffected by this method call.
666 *
667 * @param month the month-of-year to set in the returned year-month, from 1 (January) to 12 (December)
668 * @return a {@code YearMonth} based on this year-month with the requested month, not null
669 * @throws DateTimeException if the month-of-year value is invalid
670 */
671 public YearMonth withMonth(int month) {
672 MONTH_OF_YEAR.checkValidValue(month);
673 return with(year, month);
674 }
675
676 //-----------------------------------------------------------------------
677 /**
678 * Returns a copy of this year-month with the specified amount added.
679 * <p>
680 * This returns a {@code YearMonth}, based on this one, with the specified amount added.
681 * The amount is typically {@link Period} but may be any other type implementing
682 * the {@link TemporalAmount} interface.
683 * <p>
684 * The calculation is delegated to the amount object by calling
685 * {@link TemporalAmount#addTo(Temporal)}. The amount implementation is free
686 * to implement the addition in any way it wishes, however it typically
687 * calls back to {@link #plus(long, TemporalUnit)}. Consult the documentation
688 * of the amount implementation to determine if it can be successfully added.
689 * <p>
690 * This instance is immutable and unaffected by this method call.
691 *
692 * @param amountToAdd the amount to add, not null
693 * @return a {@code YearMonth} based on this year-month with the addition made, not null
694 * @throws DateTimeException if the addition cannot be made
695 * @throws ArithmeticException if numeric overflow occurs
696 */
697 @Override
698 public YearMonth plus(TemporalAmount amountToAdd) {
699 return (YearMonth) amountToAdd.addTo(this);
700 }
701
702 /**
703 * Returns a copy of this year-month with the specified amount added.
704 * <p>
705 * This returns a {@code YearMonth}, based on this one, with the amount
706 * in terms of the unit added. If it is not possible to add the amount, because the
707 * unit is not supported or for some other reason, an exception is thrown.
708 * <p>
709 * If the field is a {@link ChronoUnit} then the addition is implemented here.
710 * The supported fields behave as follows:
711 * <ul>
712 * <li>{@code MONTHS} -
713 * Returns a {@code YearMonth} with the specified number of months added.
714 * This is equivalent to {@link #plusMonths(long)}.
715 * <li>{@code YEARS} -
716 * Returns a {@code YearMonth} with the specified number of years added.
717 * This is equivalent to {@link #plusYears(long)}.
718 * <li>{@code DECADES} -
719 * Returns a {@code YearMonth} with the specified number of decades added.
720 * This is equivalent to calling {@link #plusYears(long)} with the amount
721 * multiplied by 10.
722 * <li>{@code CENTURIES} -
723 * Returns a {@code YearMonth} with the specified number of centuries added.
724 * This is equivalent to calling {@link #plusYears(long)} with the amount
725 * multiplied by 100.
726 * <li>{@code MILLENNIA} -
727 * Returns a {@code YearMonth} with the specified number of millennia added.
728 * This is equivalent to calling {@link #plusYears(long)} with the amount
729 * multiplied by 1,000.
730 * <li>{@code ERAS} -
731 * Returns a {@code YearMonth} with the specified number of eras added.
732 * Only two eras are supported so the amount must be one, zero or minus one.
733 * If the amount is non-zero then the year is changed such that the year-of-era
734 * is unchanged.
735 * </ul>
736 * <p>
737 * All other {@code ChronoUnit} instances will throw an {@code UnsupportedTemporalTypeException}.
738 * <p>
739 * If the field is not a {@code ChronoUnit}, then the result of this method
740 * is obtained by invoking {@code TemporalUnit.addTo(Temporal, long)}
741 * passing {@code this} as the argument. In this case, the unit determines
742 * whether and how to perform the addition.
743 * <p>
744 * This instance is immutable and unaffected by this method call.
745 *
746 * @param amountToAdd the amount of the unit to add to the result, may be negative
747 * @param unit the unit of the amount to add, not null
748 * @return a {@code YearMonth} based on this year-month with the specified amount added, not null
749 * @throws DateTimeException if the addition cannot be made
750 * @throws UnsupportedTemporalTypeException if the unit is not supported
751 * @throws ArithmeticException if numeric overflow occurs
752 */
753 @Override
754 public YearMonth plus(long amountToAdd, TemporalUnit unit) {
755 if (unit instanceof ChronoUnit) {
756 switch ((ChronoUnit) unit) {
757 case MONTHS: return plusMonths(amountToAdd);
758 case YEARS: return plusYears(amountToAdd);
759 case DECADES: return plusYears(Math.multiplyExact(amountToAdd, 10));
760 case CENTURIES: return plusYears(Math.multiplyExact(amountToAdd, 100));
761 case MILLENNIA: return plusYears(Math.multiplyExact(amountToAdd, 1000));
762 case ERAS: return with(ERA, Math.addExact(getLong(ERA), amountToAdd));
763 }
764 throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit.getName());
765 }
766 return unit.addTo(this, amountToAdd);
767 }
768
769 /**
770 * Returns a copy of this year-month with the specified period in years added.
771 * <p>
772 * This instance is immutable and unaffected by this method call.
773 *
774 * @param yearsToAdd the years to add, may be negative
775 * @return a {@code YearMonth} based on this year-month with the years added, not null
776 * @throws DateTimeException if the result exceeds the supported range
777 */
778 public YearMonth plusYears(long yearsToAdd) {
779 if (yearsToAdd == 0) {
780 return this;
781 }
782 int newYear = YEAR.checkValidIntValue(year + yearsToAdd); // safe overflow
783 return with(newYear, month);
784 }
785
786 /**
787 * Returns a copy of this year-month with the specified period in months added.
788 * <p>
789 * This instance is immutable and unaffected by this method call.
790 *
791 * @param monthsToAdd the months to add, may be negative
792 * @return a {@code YearMonth} based on this year-month with the months added, not null
793 * @throws DateTimeException if the result exceeds the supported range
794 */
795 public YearMonth plusMonths(long monthsToAdd) {
796 if (monthsToAdd == 0) {
797 return this;
798 }
799 long monthCount = year * 12L + (month - 1);
800 long calcMonths = monthCount + monthsToAdd; // safe overflow
801 int newYear = YEAR.checkValidIntValue(Math.floorDiv(calcMonths, 12));
802 int newMonth = (int)Math.floorMod(calcMonths, 12) + 1;
803 return with(newYear, newMonth);
804 }
805
806 //-----------------------------------------------------------------------
807 /**
808 * Returns a copy of this year-month with the specified amount subtracted.
809 * <p>
810 * This returns a {@code YearMonth}, based on this one, with the specified amount subtracted.
811 * The amount is typically {@link Period} but may be any other type implementing
812 * the {@link TemporalAmount} interface.
813 * <p>
814 * The calculation is delegated to the amount object by calling
815 * {@link TemporalAmount#subtractFrom(Temporal)}. The amount implementation is free
816 * to implement the subtraction in any way it wishes, however it typically
817 * calls back to {@link #minus(long, TemporalUnit)}. Consult the documentation
818 * of the amount implementation to determine if it can be successfully subtracted.
819 * <p>
820 * This instance is immutable and unaffected by this method call.
821 *
822 * @param amountToSubtract the amount to subtract, not null
823 * @return a {@code YearMonth} based on this year-month with the subtraction made, not null
824 * @throws DateTimeException if the subtraction cannot be made
825 * @throws ArithmeticException if numeric overflow occurs
826 */
827 @Override
828 public YearMonth minus(TemporalAmount amountToSubtract) {
829 return (YearMonth) amountToSubtract.subtractFrom(this);
830 }
831
832 /**
833 * Returns a copy of this year-month with the specified amount subtracted.
834 * <p>
835 * This returns a {@code YearMonth}, based on this one, with the amount
836 * in terms of the unit subtracted. If it is not possible to subtract the amount,
837 * because the unit is not supported or for some other reason, an exception is thrown.
838 * <p>
839 * This method is equivalent to {@link #plus(long, TemporalUnit)} with the amount negated.
840 * See that method for a full description of how addition, and thus subtraction, works.
841 * <p>
842 * This instance is immutable and unaffected by this method call.
843 *
844 * @param amountToSubtract the amount of the unit to subtract from the result, may be negative
845 * @param unit the unit of the amount to subtract, not null
846 * @return a {@code YearMonth} based on this year-month with the specified amount subtracted, not null
847 * @throws DateTimeException if the subtraction cannot be made
848 * @throws UnsupportedTemporalTypeException if the unit is not supported
849 * @throws ArithmeticException if numeric overflow occurs
850 */
851 @Override
852 public YearMonth minus(long amountToSubtract, TemporalUnit unit) {
853 return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
854 }
855
856 /**
857 * Returns a copy of this year-month with the specified period in years subtracted.
858 * <p>
859 * This instance is immutable and unaffected by this method call.
860 *
861 * @param yearsToSubtract the years to subtract, may be negative
862 * @return a {@code YearMonth} based on this year-month with the years subtracted, not null
863 * @throws DateTimeException if the result exceeds the supported range
864 */
865 public YearMonth minusYears(long yearsToSubtract) {
866 return (yearsToSubtract == Long.MIN_VALUE ? plusYears(Long.MAX_VALUE).plusYears(1) : plusYears(-yearsToSubtract));
867 }
868
869 /**
870 * Returns a copy of this year-month with the specified period in months subtracted.
871 * <p>
872 * This instance is immutable and unaffected by this method call.
873 *
874 * @param monthsToSubtract the months to subtract, may be negative
875 * @return a {@code YearMonth} based on this year-month with the months subtracted, not null
876 * @throws DateTimeException if the result exceeds the supported range
877 */
878 public YearMonth minusMonths(long monthsToSubtract) {
879 return (monthsToSubtract == Long.MIN_VALUE ? plusMonths(Long.MAX_VALUE).plusMonths(1) : plusMonths(-monthsToSubtract));
880 }
881
882 //-----------------------------------------------------------------------
883 /**
884 * Queries this year-month using the specified query.
885 * <p>
886 * This queries this year-month using the specified query strategy object.
887 * The {@code TemporalQuery} object defines the logic to be used to
888 * obtain the result. Read the documentation of the query to understand
889 * what the result of this method will be.
890 * <p>
891 * The result of this method is obtained by invoking the
892 * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the
893 * specified query passing {@code this} as the argument.
894 *
895 * @param <R> the type of the result
896 * @param query the query to invoke, not null
897 * @return the query result, null may be returned (defined by the query)
898 * @throws DateTimeException if unable to query (defined by the query)
899 * @throws ArithmeticException if numeric overflow occurs (defined by the query)
900 */
901 @SuppressWarnings("unchecked")
902 @Override
903 public <R> R query(TemporalQuery<R> query) {
904 if (query == TemporalQuery.chronology()) {
905 return (R) IsoChronology.INSTANCE;
906 } else if (query == TemporalQuery.precision()) {
907 return (R) MONTHS;
908 }
909 return Temporal.super.query(query);
910 }
911
912 /**
913 * Adjusts the specified temporal object to have this year-month.
914 * <p>
915 * This returns a temporal object of the same observable type as the input
916 * with the year and month changed to be the same as this.
917 * <p>
918 * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}
919 * passing {@link ChronoField#PROLEPTIC_MONTH} as the field.
920 * If the specified temporal object does not use the ISO calendar system then
921 * a {@code DateTimeException} is thrown.
922 * <p>
923 * In most cases, it is clearer to reverse the calling pattern by using
924 * {@link Temporal#with(TemporalAdjuster)}:
925 * <pre>
926 * // these two lines are equivalent, but the second approach is recommended
927 * temporal = thisYearMonth.adjustInto(temporal);
928 * temporal = temporal.with(thisYearMonth);
929 * </pre>
930 * <p>
931 * This instance is immutable and unaffected by this method call.
932 *
933 * @param temporal the target object to be adjusted, not null
934 * @return the adjusted object, not null
935 * @throws DateTimeException if unable to make the adjustment
936 * @throws ArithmeticException if numeric overflow occurs
937 */
938 @Override
939 public Temporal adjustInto(Temporal temporal) {
940 if (Chronology.from(temporal).equals(IsoChronology.INSTANCE) == false) {
941 throw new DateTimeException("Adjustment only supported on ISO date-time");
942 }
943 return temporal.with(PROLEPTIC_MONTH, getProlepticMonth());
944 }
945
946 /**
947 * Calculates the period between this year-month and another year-month in
948 * terms of the specified unit.
949 * <p>
950 * This calculates the period between two year-months in terms of a single unit.
951 * The start and end points are {@code this} and the specified year-month.
952 * The result will be negative if the end is before the start.
953 * The {@code Temporal} passed to this method must be a {@code YearMonth}.
954 * For example, the period in years between two year-months can be calculated
955 * using {@code startYearMonth.periodUntil(endYearMonth, YEARS)}.
956 * <p>
957 * The calculation returns a whole number, representing the number of
958 * complete units between the two year-months.
959 * For example, the period in decades between 2012-06 and 2032-05
960 * will only be one decade as it is one month short of two decades.
961 * <p>
962 * There are two equivalent ways of using this method.
963 * The first is to invoke this method.
964 * The second is to use {@link TemporalUnit#between(Temporal, Temporal)}:
965 * <pre>
966 * // these two lines are equivalent
967 * amount = start.periodUntil(end, MONTHS);
968 * amount = MONTHS.between(start, end);
969 * </pre>
970 * The choice should be made based on which makes the code more readable.
971 * <p>
972 * The calculation is implemented in this method for {@link ChronoUnit}.
973 * The units {@code MONTHS}, {@code YEARS}, {@code DECADES},
974 * {@code CENTURIES}, {@code MILLENNIA} and {@code ERAS} are supported.
975 * Other {@code ChronoUnit} values will throw an exception.
976 * <p>
977 * If the unit is not a {@code ChronoUnit}, then the result of this method
978 * is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)}
979 * passing {@code this} as the first argument and the input temporal as
980 * the second argument.
981 * <p>
982 * This instance is immutable and unaffected by this method call.
983 *
984 * @param endYearMonth the end year-month, which must be a {@code YearMonth}, not null
985 * @param unit the unit to measure the period in, not null
986 * @return the amount of the period between this year-month and the end year-month
987 * @throws DateTimeException if the period cannot be calculated
988 * @throws UnsupportedTemporalTypeException if the unit is not supported
989 * @throws ArithmeticException if numeric overflow occurs
990 */
991 @Override
992 public long periodUntil(Temporal endYearMonth, TemporalUnit unit) {
993 if (endYearMonth instanceof YearMonth == false) {
994 Objects.requireNonNull(endYearMonth, "endYearMonth");
995 throw new DateTimeException("Unable to calculate period between objects of two different types");
996 }
997 YearMonth end = (YearMonth) endYearMonth;
998 if (unit instanceof ChronoUnit) {
999 long monthsUntil = end.getProlepticMonth() - getProlepticMonth(); // no overflow
1000 switch ((ChronoUnit) unit) {
1001 case MONTHS: return monthsUntil;
1002 case YEARS: return monthsUntil / 12;
1003 case DECADES: return monthsUntil / 120;
1004 case CENTURIES: return monthsUntil / 1200;
1005 case MILLENNIA: return monthsUntil / 12000;
1006 case ERAS: return end.getLong(ERA) - getLong(ERA);
1007 }
1008 throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit.getName());
1009 }
1010 return unit.between(this, endYearMonth);
1011 }
1012
1013 /**
1014 * Formats this year-month using the specified formatter.
1015 * <p>
1016 * This year-month will be passed to the formatter to produce a string.
1017 *
1018 * @param formatter the formatter to use, not null
1019 * @return the formatted year-month string, not null
1020 * @throws DateTimeException if an error occurs during printing
1021 */
1022 public String format(DateTimeFormatter formatter) {
1023 Objects.requireNonNull(formatter, "formatter");
1024 return formatter.format(this);
1025 }
1026
1027 //-----------------------------------------------------------------------
1028 /**
1029 * Combines this year-month with a day-of-month to create a {@code LocalDate}.
1030 * <p>
1031 * This returns a {@code LocalDate} formed from this year-month and the specified day-of-month.
1032 * <p>
1033 * The day-of-month value must be valid for the year-month.
1034 * <p>
1035 * This method can be used as part of a chain to produce a date:
1036 * <pre>
1037 * LocalDate date = year.atMonth(month).atDay(day);
1038 * </pre>
1039 *
1040 * @param dayOfMonth the day-of-month to use, from 1 to 31
1041 * @return the date formed from this year-month and the specified day, not null
1042 * @throws DateTimeException if the day is invalid for the year-month
1043 * @see #isValidDay(int)
1044 */
1045 public LocalDate atDay(int dayOfMonth) {
1046 return LocalDate.of(year, month, dayOfMonth);
1047 }
1048
1049 /**
1050 * Returns a {@code LocalDate} at the end of the month.
1051 * <p>
1052 * This returns a {@code LocalDate} based on this year-month.
1053 * The day-of-month is set to the last valid day of the month, taking
1054 * into account leap years.
1055 * <p>
1056 * This method can be used as part of a chain to produce a date:
1057 * <pre>
1058 * LocalDate date = year.atMonth(month).atEndOfMonth();
1059 * </pre>
1060 *
1061 * @return the last valid date of this year-month, not null
1062 */
1063 public LocalDate atEndOfMonth() {
1064 return LocalDate.of(year, month, lengthOfMonth());
1065 }
1066
1067 //-----------------------------------------------------------------------
1068 /**
1069 * Compares this year-month to another year-month.
1070 * <p>
1071 * The comparison is based first on the value of the year, then on the value of the month.
1072 * It is "consistent with equals", as defined by {@link Comparable}.
1073 *
1074 * @param other the other year-month to compare to, not null
1075 * @return the comparator value, negative if less, positive if greater
1076 */
1077 @Override
1078 public int compareTo(YearMonth other) {
1079 int cmp = (year - other.year);
1080 if (cmp == 0) {
1081 cmp = (month - other.month);
1082 }
1083 return cmp;
1084 }
1085
1086 /**
1087 * Is this year-month after the specified year-month.
1088 *
1089 * @param other the other year-month to compare to, not null
1090 * @return true if this is after the specified year-month
1091 */
1092 public boolean isAfter(YearMonth other) {
1093 return compareTo(other) > 0;
1094 }
1095
1096 /**
1097 * Is this year-month before the specified year-month.
1098 *
1099 * @param other the other year-month to compare to, not null
1100 * @return true if this point is before the specified year-month
1101 */
1102 public boolean isBefore(YearMonth other) {
1103 return compareTo(other) < 0;
1104 }
1105
1106 //-----------------------------------------------------------------------
1107 /**
1108 * Checks if this year-month is equal to another year-month.
1109 * <p>
1110 * The comparison is based on the time-line position of the year-months.
1111 *
1112 * @param obj the object to check, null returns false
1113 * @return true if this is equal to the other year-month
1114 */
1115 @Override
1116 public boolean equals(Object obj) {
1117 if (this == obj) {
1118 return true;
1119 }
1120 if (obj instanceof YearMonth) {
1121 YearMonth other = (YearMonth) obj;
1122 return year == other.year && month == other.month;
1123 }
1124 return false;
1125 }
1126
1127 /**
1128 * A hash code for this year-month.
1129 *
1130 * @return a suitable hash code
1131 */
1132 @Override
1133 public int hashCode() {
1134 return year ^ (month << 27);
1135 }
1136
1137 //-----------------------------------------------------------------------
1138 /**
1139 * Outputs this year-month as a {@code String}, such as {@code 2007-12}.
1140 * <p>
1141 * The output will be in the format {@code uuuu-MM}:
1142 *
1143 * @return a string representation of this year-month, not null
1144 */
1145 @Override
1146 public String toString() {
1147 int absYear = Math.abs(year);
1148 StringBuilder buf = new StringBuilder(9);
1149 if (absYear < 1000) {
1150 if (year < 0) {
1151 buf.append(year - 10000).deleteCharAt(1);
1152 } else {
1153 buf.append(year + 10000).deleteCharAt(0);
1154 }
1155 } else {
1156 buf.append(year);
1157 }
1158 return buf.append(month < 10 ? "-0" : "-")
1159 .append(month)
1160 .toString();
1161 }
1162
1163 //-----------------------------------------------------------------------
1164 /**
1165 * Writes the object using a
1166 * <a href="../../../serialized-form.html#java.time.temporal.Ser">dedicated serialized form</a>.
1167 * <pre>
1168 * out.writeByte(12); // identifies this as a YearMonth
1169 * out.writeInt(year);
1170 * out.writeByte(month);
1171 * </pre>
1172 *
1173 * @return the instance of {@code Ser}, not null
1174 */
1175 private Object writeReplace() {
1176 return new Ser(Ser.YEAR_MONTH_TYPE, this);
1177 }
1178
1179 /**
1180 * Defend against malicious streams.
1181 * @return never
1182 * @throws InvalidObjectException always
1183 */
1184 private Object readResolve() throws ObjectStreamException {
1185 throw new InvalidObjectException("Deserialization via serialization delegate");
1186 }
1187
1188 void writeExternal(DataOutput out) throws IOException {
1189 out.writeInt(year);
1190 out.writeByte(month);
1191 }
1192
1193 static YearMonth readExternal(DataInput in) throws IOException {
1194 int year = in.readInt();
1195 byte month = in.readByte();
1196 return YearMonth.of(year, month);
1197 }
1198
1199 }