1 /* 2 * Copyright (c) 2012, 2019, 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.CENTURIES; 70 import static java.time.temporal.ChronoUnit.DECADES; 71 import static java.time.temporal.ChronoUnit.ERAS; 72 import static java.time.temporal.ChronoUnit.MILLENNIA; 73 import static java.time.temporal.ChronoUnit.MONTHS; 74 import static java.time.temporal.ChronoUnit.YEARS; 75 76 import java.io.DataInput; 77 import java.io.DataOutput; 78 import java.io.IOException; 79 import java.io.InvalidObjectException; 80 import java.io.ObjectInputStream; 81 import java.io.Serializable; 82 import java.time.chrono.Chronology; 83 import java.time.chrono.IsoChronology; 84 import java.time.format.DateTimeFormatter; 85 import java.time.format.DateTimeFormatterBuilder; 86 import java.time.format.DateTimeParseException; 87 import java.time.format.SignStyle; 88 import java.time.temporal.ChronoField; 89 import java.time.temporal.ChronoUnit; 90 import java.time.temporal.Temporal; 91 import java.time.temporal.TemporalAccessor; 92 import java.time.temporal.TemporalAdjuster; 93 import java.time.temporal.TemporalAmount; 94 import java.time.temporal.TemporalField; 95 import java.time.temporal.TemporalQueries; 96 import java.time.temporal.TemporalQuery; 97 import java.time.temporal.TemporalUnit; 98 import java.time.temporal.UnsupportedTemporalTypeException; 99 import java.time.temporal.ValueRange; 100 import java.util.Objects; 101 102 // Android-changed: removed ValueBased paragraph. 103 /** 104 * A year-month in the ISO-8601 calendar system, such as {@code 2007-12}. 105 * <p> 106 * {@code YearMonth} is an immutable date-time object that represents the combination 107 * of a year and month. Any field that can be derived from a year and month, such as 108 * quarter-of-year, can be obtained. 109 * <p> 110 * This class does not store or represent a day, time or time-zone. 111 * For example, the value "October 2007" can be stored in a {@code YearMonth}. 112 * <p> 113 * The ISO-8601 calendar system is the modern civil calendar system used today 114 * in most of the world. It is equivalent to the proleptic Gregorian calendar 115 * system, in which today's rules for leap years are applied for all time. 116 * For most applications written today, the ISO-8601 rules are entirely suitable. 117 * However, any application that makes use of historical dates, and requires them 118 * to be accurate will find the ISO-8601 approach unsuitable. 119 * 120 * @implSpec 121 * This class is immutable and thread-safe. 122 * 123 * @since 1.8 124 */ 125 public final class YearMonth 126 implements Temporal, TemporalAdjuster, Comparable<YearMonth>, Serializable { 127 128 /** 129 * Serialization version. 130 */ 131 @java.io.Serial 132 private static final long serialVersionUID = 4183400860270640070L; 133 /** 134 * Parser. 135 */ 136 private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder() 137 .appendValue(YEAR, 4, 10, SignStyle.EXCEEDS_PAD) 138 .appendLiteral('-') 139 .appendValue(MONTH_OF_YEAR, 2) 140 .toFormatter(); 141 142 /** 143 * The year. 144 */ 145 private final int year; 146 /** 147 * The month-of-year, not null. 148 */ 149 private final int month; 150 151 //----------------------------------------------------------------------- 152 /** 153 * Obtains the current year-month from the system clock in the default time-zone. 154 * <p> 155 * This will query the {@link Clock#systemDefaultZone() system clock} in the default 156 * time-zone to obtain the current year-month. 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 * @return the current year-month using the system clock and default time-zone, not null 162 */ now()163 public static YearMonth now() { 164 return now(Clock.systemDefaultZone()); 165 } 166 167 /** 168 * Obtains the current year-month from the system clock in the specified time-zone. 169 * <p> 170 * This will query the {@link Clock#system(ZoneId) system clock} to obtain the current year-month. 171 * Specifying the time-zone avoids dependence on the default time-zone. 172 * <p> 173 * Using this method will prevent the ability to use an alternate clock for testing 174 * because the clock is hard-coded. 175 * 176 * @param zone the zone ID to use, not null 177 * @return the current year-month using the system clock, not null 178 */ now(ZoneId zone)179 public static YearMonth now(ZoneId zone) { 180 return now(Clock.system(zone)); 181 } 182 183 /** 184 * Obtains the current year-month from the specified clock. 185 * <p> 186 * This will query the specified clock to obtain the current year-month. 187 * Using this method allows the use of an alternate clock for testing. 188 * The alternate clock may be introduced using {@link Clock dependency injection}. 189 * 190 * @param clock the clock to use, not null 191 * @return the current year-month, not null 192 */ now(Clock clock)193 public static YearMonth now(Clock clock) { 194 final LocalDate now = LocalDate.now(clock); // called once 195 return YearMonth.of(now.getYear(), now.getMonth()); 196 } 197 198 //----------------------------------------------------------------------- 199 /** 200 * Obtains an instance of {@code YearMonth} from a year and month. 201 * 202 * @param year the year to represent, from MIN_YEAR to MAX_YEAR 203 * @param month the month-of-year to represent, not null 204 * @return the year-month, not null 205 * @throws DateTimeException if the year value is invalid 206 */ of(int year, Month month)207 public static YearMonth of(int year, Month month) { 208 Objects.requireNonNull(month, "month"); 209 return of(year, month.getValue()); 210 } 211 212 /** 213 * Obtains an instance of {@code YearMonth} from a year and month. 214 * 215 * @param year the year to represent, from MIN_YEAR to MAX_YEAR 216 * @param month the month-of-year to represent, from 1 (January) to 12 (December) 217 * @return the year-month, not null 218 * @throws DateTimeException if either field value is invalid 219 */ of(int year, int month)220 public static YearMonth of(int year, int month) { 221 YEAR.checkValidValue(year); 222 MONTH_OF_YEAR.checkValidValue(month); 223 return new YearMonth(year, month); 224 } 225 226 //----------------------------------------------------------------------- 227 /** 228 * Obtains an instance of {@code YearMonth} from a temporal object. 229 * <p> 230 * This obtains a year-month based on the specified temporal. 231 * A {@code TemporalAccessor} represents an arbitrary set of date and time information, 232 * which this factory converts to an instance of {@code YearMonth}. 233 * <p> 234 * The conversion extracts the {@link ChronoField#YEAR YEAR} and 235 * {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} fields. 236 * The extraction is only permitted if the temporal object has an ISO 237 * chronology, or can be converted to a {@code LocalDate}. 238 * <p> 239 * This method matches the signature of the functional interface {@link TemporalQuery} 240 * allowing it to be used as a query via method reference, {@code YearMonth::from}. 241 * 242 * @param temporal the temporal object to convert, not null 243 * @return the year-month, not null 244 * @throws DateTimeException if unable to convert to a {@code YearMonth} 245 */ from(TemporalAccessor temporal)246 public static YearMonth from(TemporalAccessor temporal) { 247 if (temporal instanceof YearMonth) { 248 return (YearMonth) temporal; 249 } 250 Objects.requireNonNull(temporal, "temporal"); 251 try { 252 if (IsoChronology.INSTANCE.equals(Chronology.from(temporal)) == false) { 253 temporal = LocalDate.from(temporal); 254 } 255 return of(temporal.get(YEAR), temporal.get(MONTH_OF_YEAR)); 256 } catch (DateTimeException ex) { 257 throw new DateTimeException("Unable to obtain YearMonth from TemporalAccessor: " + 258 temporal + " of type " + temporal.getClass().getName(), ex); 259 } 260 } 261 262 //----------------------------------------------------------------------- 263 /** 264 * Obtains an instance of {@code YearMonth} from a text string such as {@code 2007-12}. 265 * <p> 266 * The string must represent a valid year-month. 267 * The format must be {@code uuuu-MM}. 268 * Years outside the range 0000 to 9999 must be prefixed by the plus or minus symbol. 269 * 270 * @param text the text to parse such as "2007-12", not null 271 * @return the parsed year-month, not null 272 * @throws DateTimeParseException if the text cannot be parsed 273 */ parse(CharSequence text)274 public static YearMonth parse(CharSequence text) { 275 return parse(text, PARSER); 276 } 277 278 /** 279 * Obtains an instance of {@code YearMonth} from a text string using a specific formatter. 280 * <p> 281 * The text is parsed using the formatter, returning a year-month. 282 * 283 * @param text the text to parse, not null 284 * @param formatter the formatter to use, not null 285 * @return the parsed year-month, not null 286 * @throws DateTimeParseException if the text cannot be parsed 287 */ parse(CharSequence text, DateTimeFormatter formatter)288 public static YearMonth parse(CharSequence text, DateTimeFormatter formatter) { 289 Objects.requireNonNull(formatter, "formatter"); 290 return formatter.parse(text, YearMonth::from); 291 } 292 293 //----------------------------------------------------------------------- 294 /** 295 * Constructor. 296 * 297 * @param year the year to represent, validated from MIN_YEAR to MAX_YEAR 298 * @param month the month-of-year to represent, validated from 1 (January) to 12 (December) 299 */ YearMonth(int year, int month)300 private YearMonth(int year, int month) { 301 this.year = year; 302 this.month = month; 303 } 304 305 /** 306 * Returns a copy of this year-month with the new year and month, checking 307 * to see if a new object is in fact required. 308 * 309 * @param newYear the year to represent, validated from MIN_YEAR to MAX_YEAR 310 * @param newMonth the month-of-year to represent, validated not null 311 * @return the year-month, not null 312 */ with(int newYear, int newMonth)313 private YearMonth with(int newYear, int newMonth) { 314 if (year == newYear && month == newMonth) { 315 return this; 316 } 317 return new YearMonth(newYear, newMonth); 318 } 319 320 //----------------------------------------------------------------------- 321 /** 322 * Checks if the specified field is supported. 323 * <p> 324 * This checks if this year-month can be queried for the specified field. 325 * If false, then calling the {@link #range(TemporalField) range}, 326 * {@link #get(TemporalField) get} and {@link #with(TemporalField, long)} 327 * methods will throw an exception. 328 * <p> 329 * If the field is a {@link ChronoField} then the query is implemented here. 330 * The supported fields are: 331 * <ul> 332 * <li>{@code MONTH_OF_YEAR} 333 * <li>{@code PROLEPTIC_MONTH} 334 * <li>{@code YEAR_OF_ERA} 335 * <li>{@code YEAR} 336 * <li>{@code ERA} 337 * </ul> 338 * All other {@code ChronoField} instances will return false. 339 * <p> 340 * If the field is not a {@code ChronoField}, then the result of this method 341 * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)} 342 * passing {@code this} as the argument. 343 * Whether the field is supported is determined by the field. 344 * 345 * @param field the field to check, null returns false 346 * @return true if the field is supported on this year-month, false if not 347 */ 348 @Override isSupported(TemporalField field)349 public boolean isSupported(TemporalField field) { 350 if (field instanceof ChronoField) { 351 return field == YEAR || field == MONTH_OF_YEAR || 352 field == PROLEPTIC_MONTH || field == YEAR_OF_ERA || field == ERA; 353 } 354 return field != null && field.isSupportedBy(this); 355 } 356 357 /** 358 * Checks if the specified unit is supported. 359 * <p> 360 * This checks if the specified unit can be added to, or subtracted from, this year-month. 361 * If false, then calling the {@link #plus(long, TemporalUnit)} and 362 * {@link #minus(long, TemporalUnit) minus} methods will throw an exception. 363 * <p> 364 * If the unit is a {@link ChronoUnit} then the query is implemented here. 365 * The supported units are: 366 * <ul> 367 * <li>{@code MONTHS} 368 * <li>{@code YEARS} 369 * <li>{@code DECADES} 370 * <li>{@code CENTURIES} 371 * <li>{@code MILLENNIA} 372 * <li>{@code ERAS} 373 * </ul> 374 * All other {@code ChronoUnit} instances will return false. 375 * <p> 376 * If the unit is not a {@code ChronoUnit}, then the result of this method 377 * is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)} 378 * passing {@code this} as the argument. 379 * Whether the unit is supported is determined by the unit. 380 * 381 * @param unit the unit to check, null returns false 382 * @return true if the unit can be added/subtracted, false if not 383 */ 384 @Override isSupported(TemporalUnit unit)385 public boolean isSupported(TemporalUnit unit) { 386 if (unit instanceof ChronoUnit) { 387 return unit == MONTHS || unit == YEARS || unit == DECADES || unit == CENTURIES || unit == MILLENNIA || unit == ERAS; 388 } 389 return unit != null && unit.isSupportedBy(this); 390 } 391 392 //----------------------------------------------------------------------- 393 /** 394 * Gets the range of valid values for the specified field. 395 * <p> 396 * The range object expresses the minimum and maximum valid values for a field. 397 * This year-month is used to enhance the accuracy of the returned range. 398 * If it is not possible to return the range, because the field is not supported 399 * or for some other reason, an exception is thrown. 400 * <p> 401 * If the field is a {@link ChronoField} then the query is implemented here. 402 * The {@link #isSupported(TemporalField) supported fields} will return 403 * appropriate range instances. 404 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 405 * <p> 406 * If the field is not a {@code ChronoField}, then the result of this method 407 * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)} 408 * passing {@code this} as the argument. 409 * Whether the range can be obtained is determined by the field. 410 * 411 * @param field the field to query the range for, not null 412 * @return the range of valid values for the field, not null 413 * @throws DateTimeException if the range for the field cannot be obtained 414 * @throws UnsupportedTemporalTypeException if the field is not supported 415 */ 416 @Override range(TemporalField field)417 public ValueRange range(TemporalField field) { 418 if (field == YEAR_OF_ERA) { 419 return (getYear() <= 0 ? ValueRange.of(1, Year.MAX_VALUE + 1) : ValueRange.of(1, Year.MAX_VALUE)); 420 } 421 return Temporal.super.range(field); 422 } 423 424 /** 425 * Gets the value of the specified field from this year-month as an {@code int}. 426 * <p> 427 * This queries this year-month for the value of the specified field. 428 * The returned value will always be within the valid range of values for the field. 429 * If it is not possible to return the value, because the field is not supported 430 * or for some other reason, an exception is thrown. 431 * <p> 432 * If the field is a {@link ChronoField} then the query is implemented here. 433 * The {@link #isSupported(TemporalField) supported fields} will return valid 434 * values based on this year-month, except {@code PROLEPTIC_MONTH} which is too 435 * large to fit in an {@code int} and throw a {@code DateTimeException}. 436 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 437 * <p> 438 * If the field is not a {@code ChronoField}, then the result of this method 439 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)} 440 * passing {@code this} as the argument. Whether the value can be obtained, 441 * and what the value represents, is determined by the field. 442 * 443 * @param field the field to get, not null 444 * @return the value for the field 445 * @throws DateTimeException if a value for the field cannot be obtained or 446 * the value is outside the range of valid values for the field 447 * @throws UnsupportedTemporalTypeException if the field is not supported or 448 * the range of values exceeds an {@code int} 449 * @throws ArithmeticException if numeric overflow occurs 450 */ 451 @Override // override for Javadoc get(TemporalField field)452 public int get(TemporalField field) { 453 return range(field).checkValidIntValue(getLong(field), field); 454 } 455 456 /** 457 * Gets the value of the specified field from this year-month as a {@code long}. 458 * <p> 459 * This queries this year-month for the value of the specified field. 460 * If it is not possible to return the value, because the field is not supported 461 * or for some other reason, an exception is thrown. 462 * <p> 463 * If the field is a {@link ChronoField} then the query is implemented here. 464 * The {@link #isSupported(TemporalField) supported fields} will return valid 465 * values based on this year-month. 466 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 467 * <p> 468 * If the field is not a {@code ChronoField}, then the result of this method 469 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)} 470 * passing {@code this} as the argument. Whether the value can be obtained, 471 * and what the value represents, is determined by the field. 472 * 473 * @param field the field to get, not null 474 * @return the value for the field 475 * @throws DateTimeException if a value for the field cannot be obtained 476 * @throws UnsupportedTemporalTypeException if the field is not supported 477 * @throws ArithmeticException if numeric overflow occurs 478 */ 479 @Override getLong(TemporalField field)480 public long getLong(TemporalField field) { 481 if (field instanceof ChronoField chronoField) { 482 switch (chronoField) { 483 case MONTH_OF_YEAR: return month; 484 case PROLEPTIC_MONTH: return getProlepticMonth(); 485 case YEAR_OF_ERA: return (year < 1 ? 1 - year : year); 486 case YEAR: return year; 487 case ERA: return (year < 1 ? 0 : 1); 488 } 489 throw new UnsupportedTemporalTypeException("Unsupported field: " + field); 490 } 491 return field.getFrom(this); 492 } 493 getProlepticMonth()494 private long getProlepticMonth() { 495 return (year * 12L + month - 1); 496 } 497 498 //----------------------------------------------------------------------- 499 /** 500 * Gets the year field. 501 * <p> 502 * This method returns the primitive {@code int} value for the year. 503 * <p> 504 * The year returned by this method is proleptic as per {@code get(YEAR)}. 505 * 506 * @return the year, from MIN_YEAR to MAX_YEAR 507 */ getYear()508 public int getYear() { 509 return year; 510 } 511 512 /** 513 * Gets the month-of-year field from 1 to 12. 514 * <p> 515 * This method returns the month as an {@code int} from 1 to 12. 516 * Application code is frequently clearer if the enum {@link Month} 517 * is used by calling {@link #getMonth()}. 518 * 519 * @return the month-of-year, from 1 to 12 520 * @see #getMonth() 521 */ getMonthValue()522 public int getMonthValue() { 523 return month; 524 } 525 526 /** 527 * Gets the month-of-year field using the {@code Month} enum. 528 * <p> 529 * This method returns the enum {@link Month} for the month. 530 * This avoids confusion as to what {@code int} values mean. 531 * If you need access to the primitive {@code int} value then the enum 532 * provides the {@link Month#getValue() int value}. 533 * 534 * @return the month-of-year, not null 535 * @see #getMonthValue() 536 */ getMonth()537 public Month getMonth() { 538 return Month.of(month); 539 } 540 541 //----------------------------------------------------------------------- 542 /** 543 * Checks if the year is a leap year, according to the ISO proleptic 544 * calendar system rules. 545 * <p> 546 * This method applies the current rules for leap years across the whole time-line. 547 * In general, a year is a leap year if it is divisible by four without 548 * remainder. However, years divisible by 100, are not leap years, with 549 * the exception of years divisible by 400 which are. 550 * <p> 551 * For example, 1904 is a leap year it is divisible by 4. 552 * 1900 was not a leap year as it is divisible by 100, however 2000 was a 553 * leap year as it is divisible by 400. 554 * <p> 555 * The calculation is proleptic - applying the same rules into the far future and far past. 556 * This is historically inaccurate, but is correct for the ISO-8601 standard. 557 * 558 * @return true if the year is leap, false otherwise 559 */ isLeapYear()560 public boolean isLeapYear() { 561 return IsoChronology.INSTANCE.isLeapYear(year); 562 } 563 564 /** 565 * Checks if the day-of-month is valid for this year-month. 566 * <p> 567 * This method checks whether this year and month and the input day form 568 * a valid date. 569 * 570 * @param dayOfMonth the day-of-month to validate, from 1 to 31, invalid value returns false 571 * @return true if the day is valid for this year-month 572 */ isValidDay(int dayOfMonth)573 public boolean isValidDay(int dayOfMonth) { 574 return dayOfMonth >= 1 && dayOfMonth <= lengthOfMonth(); 575 } 576 577 /** 578 * Returns the length of the month, taking account of the year. 579 * <p> 580 * This returns the length of the month in days. 581 * For example, a date in January would return 31. 582 * 583 * @return the length of the month in days, from 28 to 31 584 */ lengthOfMonth()585 public int lengthOfMonth() { 586 return getMonth().length(isLeapYear()); 587 } 588 589 /** 590 * Returns the length of the year. 591 * <p> 592 * This returns the length of the year in days, either 365 or 366. 593 * 594 * @return 366 if the year is leap, 365 otherwise 595 */ lengthOfYear()596 public int lengthOfYear() { 597 return (isLeapYear() ? 366 : 365); 598 } 599 600 //----------------------------------------------------------------------- 601 /** 602 * Returns an adjusted copy of this year-month. 603 * <p> 604 * This returns a {@code YearMonth}, based on this one, with the year-month adjusted. 605 * The adjustment takes place using the specified adjuster strategy object. 606 * Read the documentation of the adjuster to understand what adjustment will be made. 607 * <p> 608 * A simple adjuster might simply set the one of the fields, such as the year field. 609 * A more complex adjuster might set the year-month to the next month that 610 * Halley's comet will pass the Earth. 611 * <p> 612 * The result of this method is obtained by invoking the 613 * {@link TemporalAdjuster#adjustInto(Temporal)} method on the 614 * specified adjuster passing {@code this} as the argument. 615 * <p> 616 * This instance is immutable and unaffected by this method call. 617 * 618 * @param adjuster the adjuster to use, not null 619 * @return a {@code YearMonth} based on {@code this} with the adjustment made, not null 620 * @throws DateTimeException if the adjustment cannot be made 621 * @throws ArithmeticException if numeric overflow occurs 622 */ 623 @Override with(TemporalAdjuster adjuster)624 public YearMonth with(TemporalAdjuster adjuster) { 625 return (YearMonth) adjuster.adjustInto(this); 626 } 627 628 /** 629 * Returns a copy of this year-month with the specified field set to a new value. 630 * <p> 631 * This returns a {@code YearMonth}, based on this one, with the value 632 * for the specified field changed. 633 * This can be used to change any supported field, such as the year or month. 634 * If it is not possible to set the value, because the field is not supported or for 635 * some other reason, an exception is thrown. 636 * <p> 637 * If the field is a {@link ChronoField} then the adjustment is implemented here. 638 * The supported fields behave as follows: 639 * <ul> 640 * <li>{@code MONTH_OF_YEAR} - 641 * Returns a {@code YearMonth} with the specified month-of-year. 642 * The year will be unchanged. 643 * <li>{@code PROLEPTIC_MONTH} - 644 * Returns a {@code YearMonth} with the specified proleptic-month. 645 * This completely replaces the year and month of this object. 646 * <li>{@code YEAR_OF_ERA} - 647 * Returns a {@code YearMonth} with the specified year-of-era 648 * The month and era will be unchanged. 649 * <li>{@code YEAR} - 650 * Returns a {@code YearMonth} with the specified year. 651 * The month will be unchanged. 652 * <li>{@code ERA} - 653 * Returns a {@code YearMonth} with the specified era. 654 * The month and year-of-era will be unchanged. 655 * </ul> 656 * <p> 657 * In all cases, if the new value is outside the valid range of values for the field 658 * then a {@code DateTimeException} will be thrown. 659 * <p> 660 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 661 * <p> 662 * If the field is not a {@code ChronoField}, then the result of this method 663 * is obtained by invoking {@code TemporalField.adjustInto(Temporal, long)} 664 * passing {@code this} as the argument. In this case, the field determines 665 * whether and how to adjust the instant. 666 * <p> 667 * This instance is immutable and unaffected by this method call. 668 * 669 * @param field the field to set in the result, not null 670 * @param newValue the new value of the field in the result 671 * @return a {@code YearMonth} based on {@code this} with the specified field set, not null 672 * @throws DateTimeException if the field cannot be set 673 * @throws UnsupportedTemporalTypeException if the field is not supported 674 * @throws ArithmeticException if numeric overflow occurs 675 */ 676 @Override with(TemporalField field, long newValue)677 public YearMonth with(TemporalField field, long newValue) { 678 if (field instanceof ChronoField chronoField) { 679 chronoField.checkValidValue(newValue); 680 switch (chronoField) { 681 case MONTH_OF_YEAR: return withMonth((int) newValue); 682 case PROLEPTIC_MONTH: return plusMonths(newValue - getProlepticMonth()); 683 case YEAR_OF_ERA: return withYear((int) (year < 1 ? 1 - newValue : newValue)); 684 case YEAR: return withYear((int) newValue); 685 case ERA: return (getLong(ERA) == newValue ? this : withYear(1 - year)); 686 } 687 throw new UnsupportedTemporalTypeException("Unsupported field: " + field); 688 } 689 return field.adjustInto(this, newValue); 690 } 691 692 //----------------------------------------------------------------------- 693 /** 694 * Returns a copy of this {@code YearMonth} with the year altered. 695 * <p> 696 * This instance is immutable and unaffected by this method call. 697 * 698 * @param year the year to set in the returned year-month, from MIN_YEAR to MAX_YEAR 699 * @return a {@code YearMonth} based on this year-month with the requested year, not null 700 * @throws DateTimeException if the year value is invalid 701 */ withYear(int year)702 public YearMonth withYear(int year) { 703 YEAR.checkValidValue(year); 704 return with(year, month); 705 } 706 707 /** 708 * Returns a copy of this {@code YearMonth} with the month-of-year altered. 709 * <p> 710 * This instance is immutable and unaffected by this method call. 711 * 712 * @param month the month-of-year to set in the returned year-month, from 1 (January) to 12 (December) 713 * @return a {@code YearMonth} based on this year-month with the requested month, not null 714 * @throws DateTimeException if the month-of-year value is invalid 715 */ withMonth(int month)716 public YearMonth withMonth(int month) { 717 MONTH_OF_YEAR.checkValidValue(month); 718 return with(year, month); 719 } 720 721 //----------------------------------------------------------------------- 722 /** 723 * Returns a copy of this year-month with the specified amount added. 724 * <p> 725 * This returns a {@code YearMonth}, based on this one, with the specified amount added. 726 * The amount is typically {@link Period} but may be any other type implementing 727 * the {@link TemporalAmount} interface. 728 * <p> 729 * The calculation is delegated to the amount object by calling 730 * {@link TemporalAmount#addTo(Temporal)}. The amount implementation is free 731 * to implement the addition in any way it wishes, however it typically 732 * calls back to {@link #plus(long, TemporalUnit)}. Consult the documentation 733 * of the amount implementation to determine if it can be successfully added. 734 * <p> 735 * This instance is immutable and unaffected by this method call. 736 * 737 * @param amountToAdd the amount to add, not null 738 * @return a {@code YearMonth} based on this year-month with the addition made, not null 739 * @throws DateTimeException if the addition cannot be made 740 * @throws ArithmeticException if numeric overflow occurs 741 */ 742 @Override plus(TemporalAmount amountToAdd)743 public YearMonth plus(TemporalAmount amountToAdd) { 744 return (YearMonth) amountToAdd.addTo(this); 745 } 746 747 /** 748 * Returns a copy of this year-month with the specified amount added. 749 * <p> 750 * This returns a {@code YearMonth}, based on this one, with the amount 751 * in terms of the unit added. If it is not possible to add the amount, because the 752 * unit is not supported or for some other reason, an exception is thrown. 753 * <p> 754 * If the field is a {@link ChronoUnit} then the addition is implemented here. 755 * The supported fields behave as follows: 756 * <ul> 757 * <li>{@code MONTHS} - 758 * Returns a {@code YearMonth} with the specified number of months added. 759 * This is equivalent to {@link #plusMonths(long)}. 760 * <li>{@code YEARS} - 761 * Returns a {@code YearMonth} with the specified number of years added. 762 * This is equivalent to {@link #plusYears(long)}. 763 * <li>{@code DECADES} - 764 * Returns a {@code YearMonth} with the specified number of decades added. 765 * This is equivalent to calling {@link #plusYears(long)} with the amount 766 * multiplied by 10. 767 * <li>{@code CENTURIES} - 768 * Returns a {@code YearMonth} with the specified number of centuries added. 769 * This is equivalent to calling {@link #plusYears(long)} with the amount 770 * multiplied by 100. 771 * <li>{@code MILLENNIA} - 772 * Returns a {@code YearMonth} with the specified number of millennia added. 773 * This is equivalent to calling {@link #plusYears(long)} with the amount 774 * multiplied by 1,000. 775 * <li>{@code ERAS} - 776 * Returns a {@code YearMonth} with the specified number of eras added. 777 * Only two eras are supported so the amount must be one, zero or minus one. 778 * If the amount is non-zero then the year is changed such that the year-of-era 779 * is unchanged. 780 * </ul> 781 * <p> 782 * All other {@code ChronoUnit} instances will throw an {@code UnsupportedTemporalTypeException}. 783 * <p> 784 * If the field is not a {@code ChronoUnit}, then the result of this method 785 * is obtained by invoking {@code TemporalUnit.addTo(Temporal, long)} 786 * passing {@code this} as the argument. In this case, the unit determines 787 * whether and how to perform the addition. 788 * <p> 789 * This instance is immutable and unaffected by this method call. 790 * 791 * @param amountToAdd the amount of the unit to add to the result, may be negative 792 * @param unit the unit of the amount to add, not null 793 * @return a {@code YearMonth} based on this year-month with the specified amount added, not null 794 * @throws DateTimeException if the addition cannot be made 795 * @throws UnsupportedTemporalTypeException if the unit is not supported 796 * @throws ArithmeticException if numeric overflow occurs 797 */ 798 @Override plus(long amountToAdd, TemporalUnit unit)799 public YearMonth plus(long amountToAdd, TemporalUnit unit) { 800 if (unit instanceof ChronoUnit chronoUnit) { 801 switch (chronoUnit) { 802 case MONTHS: return plusMonths(amountToAdd); 803 case YEARS: return plusYears(amountToAdd); 804 case DECADES: return plusYears(Math.multiplyExact(amountToAdd, 10)); 805 case CENTURIES: return plusYears(Math.multiplyExact(amountToAdd, 100)); 806 case MILLENNIA: return plusYears(Math.multiplyExact(amountToAdd, 1000)); 807 case ERAS: return with(ERA, Math.addExact(getLong(ERA), amountToAdd)); 808 } 809 throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit); 810 } 811 return unit.addTo(this, amountToAdd); 812 } 813 814 /** 815 * Returns a copy of this {@code YearMonth} with the specified number of years added. 816 * <p> 817 * This instance is immutable and unaffected by this method call. 818 * 819 * @param yearsToAdd the years to add, may be negative 820 * @return a {@code YearMonth} based on this year-month with the years added, not null 821 * @throws DateTimeException if the result exceeds the supported range 822 */ plusYears(long yearsToAdd)823 public YearMonth plusYears(long yearsToAdd) { 824 if (yearsToAdd == 0) { 825 return this; 826 } 827 int newYear = YEAR.checkValidIntValue(year + yearsToAdd); // safe overflow 828 return with(newYear, month); 829 } 830 831 /** 832 * Returns a copy of this {@code YearMonth} with the specified number of months added. 833 * <p> 834 * This instance is immutable and unaffected by this method call. 835 * 836 * @param monthsToAdd the months to add, may be negative 837 * @return a {@code YearMonth} based on this year-month with the months added, not null 838 * @throws DateTimeException if the result exceeds the supported range 839 */ plusMonths(long monthsToAdd)840 public YearMonth plusMonths(long monthsToAdd) { 841 if (monthsToAdd == 0) { 842 return this; 843 } 844 long monthCount = year * 12L + (month - 1); 845 long calcMonths = monthCount + monthsToAdd; // safe overflow 846 int newYear = YEAR.checkValidIntValue(Math.floorDiv(calcMonths, 12)); 847 int newMonth = Math.floorMod(calcMonths, 12) + 1; 848 return with(newYear, newMonth); 849 } 850 851 //----------------------------------------------------------------------- 852 /** 853 * Returns a copy of this year-month with the specified amount subtracted. 854 * <p> 855 * This returns a {@code YearMonth}, based on this one, with the specified amount subtracted. 856 * The amount is typically {@link Period} but may be any other type implementing 857 * the {@link TemporalAmount} interface. 858 * <p> 859 * The calculation is delegated to the amount object by calling 860 * {@link TemporalAmount#subtractFrom(Temporal)}. The amount implementation is free 861 * to implement the subtraction in any way it wishes, however it typically 862 * calls back to {@link #minus(long, TemporalUnit)}. Consult the documentation 863 * of the amount implementation to determine if it can be successfully subtracted. 864 * <p> 865 * This instance is immutable and unaffected by this method call. 866 * 867 * @param amountToSubtract the amount to subtract, not null 868 * @return a {@code YearMonth} based on this year-month with the subtraction made, not null 869 * @throws DateTimeException if the subtraction cannot be made 870 * @throws ArithmeticException if numeric overflow occurs 871 */ 872 @Override minus(TemporalAmount amountToSubtract)873 public YearMonth minus(TemporalAmount amountToSubtract) { 874 return (YearMonth) amountToSubtract.subtractFrom(this); 875 } 876 877 /** 878 * Returns a copy of this year-month with the specified amount subtracted. 879 * <p> 880 * This returns a {@code YearMonth}, based on this one, with the amount 881 * in terms of the unit subtracted. If it is not possible to subtract the amount, 882 * because the unit is not supported or for some other reason, an exception is thrown. 883 * <p> 884 * This method is equivalent to {@link #plus(long, TemporalUnit)} with the amount negated. 885 * See that method for a full description of how addition, and thus subtraction, works. 886 * <p> 887 * This instance is immutable and unaffected by this method call. 888 * 889 * @param amountToSubtract the amount of the unit to subtract from the result, may be negative 890 * @param unit the unit of the amount to subtract, not null 891 * @return a {@code YearMonth} based on this year-month with the specified amount subtracted, not null 892 * @throws DateTimeException if the subtraction cannot be made 893 * @throws UnsupportedTemporalTypeException if the unit is not supported 894 * @throws ArithmeticException if numeric overflow occurs 895 */ 896 @Override minus(long amountToSubtract, TemporalUnit unit)897 public YearMonth minus(long amountToSubtract, TemporalUnit unit) { 898 return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit)); 899 } 900 901 /** 902 * Returns a copy of this {@code YearMonth} with the specified number of years subtracted. 903 * <p> 904 * This instance is immutable and unaffected by this method call. 905 * 906 * @param yearsToSubtract the years to subtract, may be negative 907 * @return a {@code YearMonth} based on this year-month with the years subtracted, not null 908 * @throws DateTimeException if the result exceeds the supported range 909 */ minusYears(long yearsToSubtract)910 public YearMonth minusYears(long yearsToSubtract) { 911 return (yearsToSubtract == Long.MIN_VALUE ? plusYears(Long.MAX_VALUE).plusYears(1) : plusYears(-yearsToSubtract)); 912 } 913 914 /** 915 * Returns a copy of this {@code YearMonth} with the specified number of months subtracted. 916 * <p> 917 * This instance is immutable and unaffected by this method call. 918 * 919 * @param monthsToSubtract the months to subtract, may be negative 920 * @return a {@code YearMonth} based on this year-month with the months subtracted, not null 921 * @throws DateTimeException if the result exceeds the supported range 922 */ minusMonths(long monthsToSubtract)923 public YearMonth minusMonths(long monthsToSubtract) { 924 return (monthsToSubtract == Long.MIN_VALUE ? plusMonths(Long.MAX_VALUE).plusMonths(1) : plusMonths(-monthsToSubtract)); 925 } 926 927 //----------------------------------------------------------------------- 928 /** 929 * Queries this year-month using the specified query. 930 * <p> 931 * This queries this year-month using the specified query strategy object. 932 * The {@code TemporalQuery} object defines the logic to be used to 933 * obtain the result. Read the documentation of the query to understand 934 * what the result of this method will be. 935 * <p> 936 * The result of this method is obtained by invoking the 937 * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the 938 * specified query passing {@code this} as the argument. 939 * 940 * @param <R> the type of the result 941 * @param query the query to invoke, not null 942 * @return the query result, null may be returned (defined by the query) 943 * @throws DateTimeException if unable to query (defined by the query) 944 * @throws ArithmeticException if numeric overflow occurs (defined by the query) 945 */ 946 @SuppressWarnings("unchecked") 947 @Override query(TemporalQuery<R> query)948 public <R> R query(TemporalQuery<R> query) { 949 if (query == TemporalQueries.chronology()) { 950 return (R) IsoChronology.INSTANCE; 951 } else if (query == TemporalQueries.precision()) { 952 return (R) MONTHS; 953 } 954 return Temporal.super.query(query); 955 } 956 957 /** 958 * Adjusts the specified temporal object to have this year-month. 959 * <p> 960 * This returns a temporal object of the same observable type as the input 961 * with the year and month changed to be the same as this. 962 * <p> 963 * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)} 964 * passing {@link ChronoField#PROLEPTIC_MONTH} as the field. 965 * If the specified temporal object does not use the ISO calendar system then 966 * a {@code DateTimeException} is thrown. 967 * <p> 968 * In most cases, it is clearer to reverse the calling pattern by using 969 * {@link Temporal#with(TemporalAdjuster)}: 970 * <pre> 971 * // these two lines are equivalent, but the second approach is recommended 972 * temporal = thisYearMonth.adjustInto(temporal); 973 * temporal = temporal.with(thisYearMonth); 974 * </pre> 975 * <p> 976 * This instance is immutable and unaffected by this method call. 977 * 978 * @param temporal the target object to be adjusted, not null 979 * @return the adjusted object, not null 980 * @throws DateTimeException if unable to make the adjustment 981 * @throws ArithmeticException if numeric overflow occurs 982 */ 983 @Override adjustInto(Temporal temporal)984 public Temporal adjustInto(Temporal temporal) { 985 if (Chronology.from(temporal).equals(IsoChronology.INSTANCE) == false) { 986 throw new DateTimeException("Adjustment only supported on ISO date-time"); 987 } 988 return temporal.with(PROLEPTIC_MONTH, getProlepticMonth()); 989 } 990 991 /** 992 * Calculates the amount of time until another year-month in terms of the specified unit. 993 * <p> 994 * This calculates the amount of time between two {@code YearMonth} 995 * objects in terms of a single {@code TemporalUnit}. 996 * The start and end points are {@code this} and the specified year-month. 997 * The result will be negative if the end is before the start. 998 * The {@code Temporal} passed to this method is converted to a 999 * {@code YearMonth} using {@link #from(TemporalAccessor)}. 1000 * For example, the amount in years between two year-months can be calculated 1001 * using {@code startYearMonth.until(endYearMonth, YEARS)}. 1002 * <p> 1003 * The calculation returns a whole number, representing the number of 1004 * complete units between the two year-months. 1005 * For example, the amount in decades between 2012-06 and 2032-05 1006 * will only be one decade as it is one month short of two decades. 1007 * <p> 1008 * There are two equivalent ways of using this method. 1009 * The first is to invoke this method. 1010 * The second is to use {@link TemporalUnit#between(Temporal, Temporal)}: 1011 * <pre> 1012 * // these two lines are equivalent 1013 * amount = start.until(end, MONTHS); 1014 * amount = MONTHS.between(start, end); 1015 * </pre> 1016 * The choice should be made based on which makes the code more readable. 1017 * <p> 1018 * The calculation is implemented in this method for {@link ChronoUnit}. 1019 * The units {@code MONTHS}, {@code YEARS}, {@code DECADES}, 1020 * {@code CENTURIES}, {@code MILLENNIA} and {@code ERAS} are supported. 1021 * Other {@code ChronoUnit} values will throw an exception. 1022 * <p> 1023 * If the unit is not a {@code ChronoUnit}, then the result of this method 1024 * is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)} 1025 * passing {@code this} as the first argument and the converted input temporal 1026 * as the second argument. 1027 * <p> 1028 * This instance is immutable and unaffected by this method call. 1029 * 1030 * @param endExclusive the end date, exclusive, which is converted to a {@code YearMonth}, not null 1031 * @param unit the unit to measure the amount in, not null 1032 * @return the amount of time between this year-month and the end year-month 1033 * @throws DateTimeException if the amount cannot be calculated, or the end 1034 * temporal cannot be converted to a {@code YearMonth} 1035 * @throws UnsupportedTemporalTypeException if the unit is not supported 1036 * @throws ArithmeticException if numeric overflow occurs 1037 */ 1038 @Override until(Temporal endExclusive, TemporalUnit unit)1039 public long until(Temporal endExclusive, TemporalUnit unit) { 1040 YearMonth end = YearMonth.from(endExclusive); 1041 if (unit instanceof ChronoUnit chronoUnit) { 1042 long monthsUntil = end.getProlepticMonth() - getProlepticMonth(); // no overflow 1043 switch (chronoUnit) { 1044 case MONTHS: return monthsUntil; 1045 case YEARS: return monthsUntil / 12; 1046 case DECADES: return monthsUntil / 120; 1047 case CENTURIES: return monthsUntil / 1200; 1048 case MILLENNIA: return monthsUntil / 12000; 1049 case ERAS: return end.getLong(ERA) - getLong(ERA); 1050 } 1051 throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit); 1052 } 1053 return unit.between(this, end); 1054 } 1055 1056 /** 1057 * Formats this year-month using the specified formatter. 1058 * <p> 1059 * This year-month will be passed to the formatter to produce a string. 1060 * 1061 * @param formatter the formatter to use, not null 1062 * @return the formatted year-month string, not null 1063 * @throws DateTimeException if an error occurs during printing 1064 */ format(DateTimeFormatter formatter)1065 public String format(DateTimeFormatter formatter) { 1066 Objects.requireNonNull(formatter, "formatter"); 1067 return formatter.format(this); 1068 } 1069 1070 //----------------------------------------------------------------------- 1071 /** 1072 * Combines this year-month with a day-of-month to create a {@code LocalDate}. 1073 * <p> 1074 * This returns a {@code LocalDate} formed from this year-month and the specified day-of-month. 1075 * <p> 1076 * The day-of-month value must be valid for the year-month. 1077 * <p> 1078 * This method can be used as part of a chain to produce a date: 1079 * <pre> 1080 * LocalDate date = year.atMonth(month).atDay(day); 1081 * </pre> 1082 * 1083 * @param dayOfMonth the day-of-month to use, from 1 to 31 1084 * @return the date formed from this year-month and the specified day, not null 1085 * @throws DateTimeException if the day is invalid for the year-month 1086 * @see #isValidDay(int) 1087 */ atDay(int dayOfMonth)1088 public LocalDate atDay(int dayOfMonth) { 1089 return LocalDate.of(year, month, dayOfMonth); 1090 } 1091 1092 /** 1093 * Returns a {@code LocalDate} at the end of the month. 1094 * <p> 1095 * This returns a {@code LocalDate} based on this year-month. 1096 * The day-of-month is set to the last valid day of the month, taking 1097 * into account leap years. 1098 * <p> 1099 * This method can be used as part of a chain to produce a date: 1100 * <pre> 1101 * LocalDate date = year.atMonth(month).atEndOfMonth(); 1102 * </pre> 1103 * 1104 * @return the last valid date of this year-month, not null 1105 */ atEndOfMonth()1106 public LocalDate atEndOfMonth() { 1107 return LocalDate.of(year, month, lengthOfMonth()); 1108 } 1109 1110 //----------------------------------------------------------------------- 1111 /** 1112 * Compares this year-month to another year-month. 1113 * <p> 1114 * The comparison is based first on the value of the year, then on the value of the month. 1115 * It is "consistent with equals", as defined by {@link Comparable}. 1116 * 1117 * @param other the other year-month to compare to, not null 1118 * @return the comparator value, negative if less, positive if greater 1119 */ 1120 @Override compareTo(YearMonth other)1121 public int compareTo(YearMonth other) { 1122 int cmp = (year - other.year); 1123 if (cmp == 0) { 1124 cmp = (month - other.month); 1125 } 1126 return cmp; 1127 } 1128 1129 /** 1130 * Checks if this year-month is after the specified year-month. 1131 * 1132 * @param other the other year-month to compare to, not null 1133 * @return true if this is after the specified year-month 1134 */ isAfter(YearMonth other)1135 public boolean isAfter(YearMonth other) { 1136 return compareTo(other) > 0; 1137 } 1138 1139 /** 1140 * Checks if this year-month is before the specified year-month. 1141 * 1142 * @param other the other year-month to compare to, not null 1143 * @return true if this point is before the specified year-month 1144 */ isBefore(YearMonth other)1145 public boolean isBefore(YearMonth other) { 1146 return compareTo(other) < 0; 1147 } 1148 1149 //----------------------------------------------------------------------- 1150 /** 1151 * Checks if this year-month is equal to another year-month. 1152 * <p> 1153 * The comparison is based on the time-line position of the year-months. 1154 * 1155 * @param obj the object to check, null returns false 1156 * @return true if this is equal to the other year-month 1157 */ 1158 @Override equals(Object obj)1159 public boolean equals(Object obj) { 1160 if (this == obj) { 1161 return true; 1162 } 1163 return (obj instanceof YearMonth other) 1164 && year == other.year 1165 && month == other.month; 1166 } 1167 1168 /** 1169 * A hash code for this year-month. 1170 * 1171 * @return a suitable hash code 1172 */ 1173 @Override hashCode()1174 public int hashCode() { 1175 return year ^ (month << 27); 1176 } 1177 1178 //----------------------------------------------------------------------- 1179 /** 1180 * Outputs this year-month as a {@code String}, such as {@code 2007-12}. 1181 * <p> 1182 * The output will be in the format {@code uuuu-MM}: 1183 * 1184 * @return a string representation of this year-month, not null 1185 */ 1186 @Override toString()1187 public String toString() { 1188 int absYear = Math.abs(year); 1189 StringBuilder buf = new StringBuilder(9); 1190 if (absYear < 1000) { 1191 if (year < 0) { 1192 buf.append(year - 10000).deleteCharAt(1); 1193 } else { 1194 buf.append(year + 10000).deleteCharAt(0); 1195 } 1196 } else { 1197 buf.append(year); 1198 } 1199 return buf.append(month < 10 ? "-0" : "-") 1200 .append(month) 1201 .toString(); 1202 } 1203 1204 //----------------------------------------------------------------------- 1205 /** 1206 * Writes the object using a 1207 * <a href="{@docRoot}/serialized-form.html#java.time.Ser">dedicated serialized form</a>. 1208 * @serialData 1209 * <pre> 1210 * out.writeByte(12); // identifies a YearMonth 1211 * out.writeInt(year); 1212 * out.writeByte(month); 1213 * </pre> 1214 * 1215 * @return the instance of {@code Ser}, not null 1216 */ 1217 @java.io.Serial writeReplace()1218 private Object writeReplace() { 1219 return new Ser(Ser.YEAR_MONTH_TYPE, this); 1220 } 1221 1222 /** 1223 * Defend against malicious streams. 1224 * 1225 * @param s the stream to read 1226 * @throws InvalidObjectException always 1227 */ 1228 @java.io.Serial readObject(ObjectInputStream s)1229 private void readObject(ObjectInputStream s) throws InvalidObjectException { 1230 throw new InvalidObjectException("Deserialization via serialization delegate"); 1231 } 1232 writeExternal(DataOutput out)1233 void writeExternal(DataOutput out) throws IOException { 1234 out.writeInt(year); 1235 out.writeByte(month); 1236 } 1237 readExternal(DataInput in)1238 static YearMonth readExternal(DataInput in) throws IOException { 1239 int year = in.readInt(); 1240 byte month = in.readByte(); 1241 return YearMonth.of(year, month); 1242 } 1243 1244 } 1245