1 /* 2 * Copyright (c) 2012, 2018, 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 /** 103 * A year-month in the ISO-8601 calendar system, such as {@code 2007-12}. 104 * <p> 105 * {@code YearMonth} is an immutable date-time object that represents the combination 106 * of a year and month. Any field that can be derived from a year and month, such as 107 * quarter-of-year, can be obtained. 108 * <p> 109 * This class does not store or represent a day, time or time-zone. 110 * For example, the value "October 2007" can be stored in a {@code YearMonth}. 111 * <p> 112 * The ISO-8601 calendar system is the modern civil calendar system used today 113 * in most of the world. It is equivalent to the proleptic Gregorian calendar 114 * system, in which today's rules for leap years are applied for all time. 115 * For most applications written today, the ISO-8601 rules are entirely suitable. 116 * However, any application that makes use of historical dates, and requires them 117 * to be accurate will find the ISO-8601 approach unsuitable. 118 * 119 * <p> 120 * This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a> 121 * class; use of identity-sensitive operations (including reference equality 122 * ({@code ==}), identity hash code, or synchronization) on instances of 123 * {@code YearMonth} may have unpredictable results and should be avoided. 124 * The {@code equals} method should be used for comparisons. 125 * 126 * @implSpec 127 * This class is immutable and thread-safe. 128 * 129 * @since 1.8 130 */ 131 public final class YearMonth 132 implements Temporal, TemporalAdjuster, Comparable<YearMonth>, Serializable { 133 134 /** 135 * Serialization version. 136 */ 137 @java.io.Serial 138 private static final long serialVersionUID = 4183400860270640070L; 139 /** 140 * Parser. 141 */ 142 private static final DateTimeFormatter PARSER = new DateTimeFormatterBuilder() 143 .appendValue(YEAR, 4, 10, SignStyle.EXCEEDS_PAD) 144 .appendLiteral('-') 145 .appendValue(MONTH_OF_YEAR, 2) 146 .toFormatter(); 147 148 /** 149 * The year. 150 */ 151 private final int year; 152 /** 153 * The month-of-year, not null. 154 */ 155 private final int month; 156 157 //----------------------------------------------------------------------- 158 /** 159 * Obtains the current year-month from the system clock in the default time-zone. 160 * <p> 161 * This will query the {@link Clock#systemDefaultZone() system clock} in the default 162 * time-zone to obtain the current year-month. 163 * <p> 164 * Using this method will prevent the ability to use an alternate clock for testing 165 * because the clock is hard-coded. 166 * 167 * @return the current year-month using the system clock and default time-zone, not null 168 */ 169 public static YearMonth now() { 170 return now(Clock.systemDefaultZone()); 171 } 172 173 /** 174 * Obtains the current year-month from the system clock in the specified time-zone. 175 * <p> 176 * This will query the {@link Clock#system(ZoneId) system clock} to obtain the current year-month. 177 * Specifying the time-zone avoids dependence on the default time-zone. 178 * <p> 179 * Using this method will prevent the ability to use an alternate clock for testing 180 * because the clock is hard-coded. 181 * 182 * @param zone the zone ID to use, not null 183 * @return the current year-month using the system clock, not null 184 */ 185 public static YearMonth now(ZoneId zone) { 186 return now(Clock.system(zone)); 187 } 188 189 /** 190 * Obtains the current year-month from the specified clock. 191 * <p> 192 * This will query the specified clock to obtain the current year-month. 193 * Using this method allows the use of an alternate clock for testing. 194 * The alternate clock may be introduced using {@link Clock dependency injection}. 195 * 196 * @param clock the clock to use, not null 197 * @return the current year-month, not null 198 */ 199 public static YearMonth now(Clock clock) { 200 final LocalDate now = LocalDate.now(clock); // called once 201 return YearMonth.of(now.getYear(), now.getMonth()); 202 } 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, not null 210 * @return the year-month, not null 211 * @throws DateTimeException if the year value is invalid 212 */ 213 public static YearMonth of(int year, Month month) { 214 Objects.requireNonNull(month, "month"); 215 return of(year, month.getValue()); 216 } 217 218 /** 219 * Obtains an instance of {@code YearMonth} from a year and month. 220 * 221 * @param year the year to represent, from MIN_YEAR to MAX_YEAR 222 * @param month the month-of-year to represent, from 1 (January) to 12 (December) 223 * @return the year-month, not null 224 * @throws DateTimeException if either field value is invalid 225 */ 226 public static YearMonth of(int year, int month) { 227 YEAR.checkValidValue(year); 228 MONTH_OF_YEAR.checkValidValue(month); 229 return new YearMonth(year, month); 230 } 231 232 //----------------------------------------------------------------------- 233 /** 234 * Obtains an instance of {@code YearMonth} from a temporal object. 235 * <p> 236 * This obtains a year-month based on the specified temporal. 237 * A {@code TemporalAccessor} represents an arbitrary set of date and time information, 238 * which this factory converts to an instance of {@code YearMonth}. 239 * <p> 240 * The conversion extracts the {@link ChronoField#YEAR YEAR} and 241 * {@link ChronoField#MONTH_OF_YEAR MONTH_OF_YEAR} fields. 242 * The extraction is only permitted if the temporal object has an ISO 243 * chronology, or can be converted to a {@code LocalDate}. 244 * <p> 245 * This method matches the signature of the functional interface {@link TemporalQuery} 246 * allowing it to be used as a query via method reference, {@code YearMonth::from}. 247 * 248 * @param temporal the temporal object to convert, not null 249 * @return the year-month, not null 250 * @throws DateTimeException if unable to convert to a {@code YearMonth} 251 */ 252 public static YearMonth from(TemporalAccessor temporal) { 253 if (temporal instanceof YearMonth) { 254 return (YearMonth) temporal; 255 } 256 Objects.requireNonNull(temporal, "temporal"); 257 try { 258 if (IsoChronology.INSTANCE.equals(Chronology.from(temporal)) == false) { 259 temporal = LocalDate.from(temporal); 260 } 261 return of(temporal.get(YEAR), temporal.get(MONTH_OF_YEAR)); 262 } catch (DateTimeException ex) { 263 throw new DateTimeException("Unable to obtain YearMonth from TemporalAccessor: " + 264 temporal + " of type " + temporal.getClass().getName(), ex); 265 } 266 } 267 268 //----------------------------------------------------------------------- 269 /** 270 * Obtains an instance of {@code YearMonth} from a text string such as {@code 2007-12}. 271 * <p> 272 * The string must represent a valid year-month. 273 * The format must be {@code uuuu-MM}. 274 * Years outside the range 0000 to 9999 must be prefixed by the plus or minus symbol. 275 * 276 * @param text the text to parse such as "2007-12", not null 277 * @return the parsed year-month, not null 278 * @throws DateTimeParseException if the text cannot be parsed 279 */ 280 public static YearMonth parse(CharSequence text) { 281 return parse(text, PARSER); 282 } 283 284 /** 285 * Obtains an instance of {@code YearMonth} from a text string using a specific formatter. 286 * <p> 287 * The text is parsed using the formatter, returning a year-month. 288 * 289 * @param text the text to parse, not null 290 * @param formatter the formatter to use, not null 291 * @return the parsed year-month, not null 292 * @throws DateTimeParseException if the text cannot be parsed 293 */ 294 public static YearMonth parse(CharSequence text, DateTimeFormatter formatter) { 295 Objects.requireNonNull(formatter, "formatter"); 296 return formatter.parse(text, YearMonth::from); 297 } 298 299 //----------------------------------------------------------------------- 300 /** 301 * Constructor. 302 * 303 * @param year the year to represent, validated from MIN_YEAR to MAX_YEAR 304 * @param month the month-of-year to represent, validated from 1 (January) to 12 (December) 305 */ 306 private YearMonth(int year, int month) { 307 this.year = year; 308 this.month = month; 309 } 310 311 /** 312 * Returns a copy of this year-month with the new year and month, checking 313 * to see if a new object is in fact required. 314 * 315 * @param newYear the year to represent, validated from MIN_YEAR to MAX_YEAR 316 * @param newMonth the month-of-year to represent, validated not null 317 * @return the year-month, not null 318 */ 319 private YearMonth with(int newYear, int newMonth) { 320 if (year == newYear && month == newMonth) { 321 return this; 322 } 323 return new YearMonth(newYear, newMonth); 324 } 325 326 //----------------------------------------------------------------------- 327 /** 328 * Checks if the specified field is supported. 329 * <p> 330 * This checks if this year-month can be queried for the specified field. 331 * If false, then calling the {@link #range(TemporalField) range}, 332 * {@link #get(TemporalField) get} and {@link #with(TemporalField, long)} 333 * methods will throw an exception. 334 * <p> 335 * If the field is a {@link ChronoField} then the query is implemented here. 336 * The supported fields are: 337 * <ul> 338 * <li>{@code MONTH_OF_YEAR} 339 * <li>{@code PROLEPTIC_MONTH} 340 * <li>{@code YEAR_OF_ERA} 341 * <li>{@code YEAR} 342 * <li>{@code ERA} 343 * </ul> 344 * All other {@code ChronoField} instances will return false. 345 * <p> 346 * If the field is not a {@code ChronoField}, then the result of this method 347 * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)} 348 * passing {@code this} as the argument. 349 * Whether the field is supported is determined by the field. 350 * 351 * @param field the field to check, null returns false 352 * @return true if the field is supported on this year-month, false if not 353 */ 354 @Override 355 public boolean isSupported(TemporalField field) { 356 if (field instanceof ChronoField) { 357 return field == YEAR || field == MONTH_OF_YEAR || 358 field == PROLEPTIC_MONTH || field == YEAR_OF_ERA || field == ERA; 359 } 360 return field != null && field.isSupportedBy(this); 361 } 362 363 /** 364 * Checks if the specified unit is supported. 365 * <p> 366 * This checks if the specified unit can be added to, or subtracted from, this year-month. 367 * If false, then calling the {@link #plus(long, TemporalUnit)} and 368 * {@link #minus(long, TemporalUnit) minus} methods will throw an exception. 369 * <p> 370 * If the unit is a {@link ChronoUnit} then the query is implemented here. 371 * The supported units are: 372 * <ul> 373 * <li>{@code MONTHS} 374 * <li>{@code YEARS} 375 * <li>{@code DECADES} 376 * <li>{@code CENTURIES} 377 * <li>{@code MILLENNIA} 378 * <li>{@code ERAS} 379 * </ul> 380 * All other {@code ChronoUnit} instances will return false. 381 * <p> 382 * If the unit is not a {@code ChronoUnit}, then the result of this method 383 * is obtained by invoking {@code TemporalUnit.isSupportedBy(Temporal)} 384 * passing {@code this} as the argument. 385 * Whether the unit is supported is determined by the unit. 386 * 387 * @param unit the unit to check, null returns false 388 * @return true if the unit can be added/subtracted, false if not 389 */ 390 @Override 391 public boolean isSupported(TemporalUnit unit) { 392 if (unit instanceof ChronoUnit) { 393 return unit == MONTHS || unit == YEARS || unit == DECADES || unit == CENTURIES || unit == MILLENNIA || unit == ERAS; 394 } 395 return unit != null && unit.isSupportedBy(this); 396 } 397 398 //----------------------------------------------------------------------- 399 /** 400 * Gets the range of valid values for the specified field. 401 * <p> 402 * The range object expresses the minimum and maximum valid values for a field. 403 * This year-month is used to enhance the accuracy of the returned range. 404 * If it is not possible to return the range, because the field is not supported 405 * or for some other reason, an exception is thrown. 406 * <p> 407 * If the field is a {@link ChronoField} then the query is implemented here. 408 * The {@link #isSupported(TemporalField) supported fields} will return 409 * appropriate range instances. 410 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 411 * <p> 412 * If the field is not a {@code ChronoField}, then the result of this method 413 * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)} 414 * passing {@code this} as the argument. 415 * Whether the range can be obtained is determined by the field. 416 * 417 * @param field the field to query the range for, not null 418 * @return the range of valid values for the field, not null 419 * @throws DateTimeException if the range for the field cannot be obtained 420 * @throws UnsupportedTemporalTypeException if the field is not supported 421 */ 422 @Override 423 public ValueRange range(TemporalField field) { 424 if (field == YEAR_OF_ERA) { 425 return (getYear() <= 0 ? ValueRange.of(1, Year.MAX_VALUE + 1) : ValueRange.of(1, Year.MAX_VALUE)); 426 } 427 return Temporal.super.range(field); 428 } 429 430 /** 431 * Gets the value of the specified field from this year-month as an {@code int}. 432 * <p> 433 * This queries this year-month for the value of the specified field. 434 * The returned value will always be within the valid range of values for the field. 435 * If it is not possible to return the value, because the field is not supported 436 * or for some other reason, an exception is thrown. 437 * <p> 438 * If the field is a {@link ChronoField} then the query is implemented here. 439 * The {@link #isSupported(TemporalField) supported fields} will return valid 440 * values based on this year-month, except {@code PROLEPTIC_MONTH} which is too 441 * large to fit in an {@code int} and throw a {@code DateTimeException}. 442 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 443 * <p> 444 * If the field is not a {@code ChronoField}, then the result of this method 445 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)} 446 * passing {@code this} as the argument. Whether the value can be obtained, 447 * and what the value represents, is determined by the field. 448 * 449 * @param field the field to get, not null 450 * @return the value for the field 451 * @throws DateTimeException if a value for the field cannot be obtained or 452 * the value is outside the range of valid values for the field 453 * @throws UnsupportedTemporalTypeException if the field is not supported or 454 * the range of values exceeds an {@code int} 455 * @throws ArithmeticException if numeric overflow occurs 456 */ 457 @Override // override for Javadoc 458 public int get(TemporalField field) { 459 return range(field).checkValidIntValue(getLong(field), field); 460 } 461 462 /** 463 * Gets the value of the specified field from this year-month as a {@code long}. 464 * <p> 465 * This queries this year-month for the value of the specified field. 466 * If it is not possible to return the value, because the field is not supported 467 * or for some other reason, an exception is thrown. 468 * <p> 469 * If the field is a {@link ChronoField} then the query is implemented here. 470 * The {@link #isSupported(TemporalField) supported fields} will return valid 471 * values based on this year-month. 472 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 473 * <p> 474 * If the field is not a {@code ChronoField}, then the result of this method 475 * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)} 476 * passing {@code this} as the argument. Whether the value can be obtained, 477 * and what the value represents, is determined by the field. 478 * 479 * @param field the field to get, not null 480 * @return the value for the field 481 * @throws DateTimeException if a value for the field cannot be obtained 482 * @throws UnsupportedTemporalTypeException if the field is not supported 483 * @throws ArithmeticException if numeric overflow occurs 484 */ 485 @Override 486 public long getLong(TemporalField field) { 487 if (field instanceof ChronoField) { 488 switch ((ChronoField) field) { 489 case MONTH_OF_YEAR: return month; 490 case PROLEPTIC_MONTH: return getProlepticMonth(); 491 case YEAR_OF_ERA: return (year < 1 ? 1 - year : year); 492 case YEAR: return year; 493 case ERA: return (year < 1 ? 0 : 1); 494 } 495 throw new UnsupportedTemporalTypeException("Unsupported field: " + field); 496 } 497 return field.getFrom(this); 498 } 499 500 private long getProlepticMonth() { 501 return (year * 12L + month - 1); 502 } 503 504 //----------------------------------------------------------------------- 505 /** 506 * Gets the year field. 507 * <p> 508 * This method returns the primitive {@code int} value for the year. 509 * <p> 510 * The year returned by this method is proleptic as per {@code get(YEAR)}. 511 * 512 * @return the year, from MIN_YEAR to MAX_YEAR 513 */ 514 public int getYear() { 515 return year; 516 } 517 518 /** 519 * Gets the month-of-year field from 1 to 12. 520 * <p> 521 * This method returns the month as an {@code int} from 1 to 12. 522 * Application code is frequently clearer if the enum {@link Month} 523 * is used by calling {@link #getMonth()}. 524 * 525 * @return the month-of-year, from 1 to 12 526 * @see #getMonth() 527 */ 528 public int getMonthValue() { 529 return month; 530 } 531 532 /** 533 * Gets the month-of-year field using the {@code Month} enum. 534 * <p> 535 * This method returns the enum {@link Month} for the month. 536 * This avoids confusion as to what {@code int} values mean. 537 * If you need access to the primitive {@code int} value then the enum 538 * provides the {@link Month#getValue() int value}. 539 * 540 * @return the month-of-year, not null 541 * @see #getMonthValue() 542 */ 543 public Month getMonth() { 544 return Month.of(month); 545 } 546 547 //----------------------------------------------------------------------- 548 /** 549 * Checks if the year is a leap year, according to the ISO proleptic 550 * calendar system rules. 551 * <p> 552 * This method applies the current rules for leap years across the whole time-line. 553 * In general, a year is a leap year if it is divisible by four without 554 * remainder. However, years divisible by 100, are not leap years, with 555 * the exception of years divisible by 400 which are. 556 * <p> 557 * For example, 1904 is a leap year it is divisible by 4. 558 * 1900 was not a leap year as it is divisible by 100, however 2000 was a 559 * leap year as it is divisible by 400. 560 * <p> 561 * The calculation is proleptic - applying the same rules into the far future and far past. 562 * This is historically inaccurate, but is correct for the ISO-8601 standard. 563 * 564 * @return true if the year is leap, false otherwise 565 */ 566 public boolean isLeapYear() { 567 return IsoChronology.INSTANCE.isLeapYear(year); 568 } 569 570 /** 571 * Checks if the day-of-month is valid for this year-month. 572 * <p> 573 * This method checks whether this year and month and the input day form 574 * a valid date. 575 * 576 * @param dayOfMonth the day-of-month to validate, from 1 to 31, invalid value returns false 577 * @return true if the day is valid for this year-month 578 */ 579 public boolean isValidDay(int dayOfMonth) { 580 return dayOfMonth >= 1 && dayOfMonth <= lengthOfMonth(); 581 } 582 583 /** 584 * Returns the length of the month, taking account of the year. 585 * <p> 586 * This returns the length of the month in days. 587 * For example, a date in January would return 31. 588 * 589 * @return the length of the month in days, from 28 to 31 590 */ 591 public int lengthOfMonth() { 592 return getMonth().length(isLeapYear()); 593 } 594 595 /** 596 * Returns the length of the year. 597 * <p> 598 * This returns the length of the year in days, either 365 or 366. 599 * 600 * @return 366 if the year is leap, 365 otherwise 601 */ 602 public int lengthOfYear() { 603 return (isLeapYear() ? 366 : 365); 604 } 605 606 //----------------------------------------------------------------------- 607 /** 608 * Returns an adjusted copy of this year-month. 609 * <p> 610 * This returns a {@code YearMonth}, based on this one, with the year-month adjusted. 611 * The adjustment takes place using the specified adjuster strategy object. 612 * Read the documentation of the adjuster to understand what adjustment will be made. 613 * <p> 614 * A simple adjuster might simply set the one of the fields, such as the year field. 615 * A more complex adjuster might set the year-month to the next month that 616 * Halley's comet will pass the Earth. 617 * <p> 618 * The result of this method is obtained by invoking the 619 * {@link TemporalAdjuster#adjustInto(Temporal)} method on the 620 * specified adjuster passing {@code this} as the argument. 621 * <p> 622 * This instance is immutable and unaffected by this method call. 623 * 624 * @param adjuster the adjuster to use, not null 625 * @return a {@code YearMonth} based on {@code this} with the adjustment made, not null 626 * @throws DateTimeException if the adjustment cannot be made 627 * @throws ArithmeticException if numeric overflow occurs 628 */ 629 @Override 630 public YearMonth with(TemporalAdjuster adjuster) { 631 return (YearMonth) adjuster.adjustInto(this); 632 } 633 634 /** 635 * Returns a copy of this year-month with the specified field set to a new value. 636 * <p> 637 * This returns a {@code YearMonth}, based on this one, with the value 638 * for the specified field changed. 639 * This can be used to change any supported field, such as the year or month. 640 * If it is not possible to set the value, because the field is not supported or for 641 * some other reason, an exception is thrown. 642 * <p> 643 * If the field is a {@link ChronoField} then the adjustment is implemented here. 644 * The supported fields behave as follows: 645 * <ul> 646 * <li>{@code MONTH_OF_YEAR} - 647 * Returns a {@code YearMonth} with the specified month-of-year. 648 * The year will be unchanged. 649 * <li>{@code PROLEPTIC_MONTH} - 650 * Returns a {@code YearMonth} with the specified proleptic-month. 651 * This completely replaces the year and month of this object. 652 * <li>{@code YEAR_OF_ERA} - 653 * Returns a {@code YearMonth} with the specified year-of-era 654 * The month and era will be unchanged. 655 * <li>{@code YEAR} - 656 * Returns a {@code YearMonth} with the specified year. 657 * The month will be unchanged. 658 * <li>{@code ERA} - 659 * Returns a {@code YearMonth} with the specified era. 660 * The month and year-of-era will be unchanged. 661 * </ul> 662 * <p> 663 * In all cases, if the new value is outside the valid range of values for the field 664 * then a {@code DateTimeException} will be thrown. 665 * <p> 666 * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. 667 * <p> 668 * If the field is not a {@code ChronoField}, then the result of this method 669 * is obtained by invoking {@code TemporalField.adjustInto(Temporal, long)} 670 * passing {@code this} as the argument. In this case, the field determines 671 * whether and how to adjust the instant. 672 * <p> 673 * This instance is immutable and unaffected by this method call. 674 * 675 * @param field the field to set in the result, not null 676 * @param newValue the new value of the field in the result 677 * @return a {@code YearMonth} based on {@code this} with the specified field set, not null 678 * @throws DateTimeException if the field cannot be set 679 * @throws UnsupportedTemporalTypeException if the field is not supported 680 * @throws ArithmeticException if numeric overflow occurs 681 */ 682 @Override 683 public YearMonth with(TemporalField field, long newValue) { 684 if (field instanceof ChronoField) { 685 ChronoField f = (ChronoField) field; 686 f.checkValidValue(newValue); 687 switch (f) { 688 case MONTH_OF_YEAR: return withMonth((int) newValue); 689 case PROLEPTIC_MONTH: return plusMonths(newValue - getProlepticMonth()); 690 case YEAR_OF_ERA: return withYear((int) (year < 1 ? 1 - newValue : newValue)); 691 case YEAR: return withYear((int) newValue); 692 case ERA: return (getLong(ERA) == newValue ? this : withYear(1 - year)); 693 } 694 throw new UnsupportedTemporalTypeException("Unsupported field: " + field); 695 } 696 return field.adjustInto(this, newValue); 697 } 698 699 //----------------------------------------------------------------------- 700 /** 701 * Returns a copy of this {@code YearMonth} with the year altered. 702 * <p> 703 * This instance is immutable and unaffected by this method call. 704 * 705 * @param year the year to set in the returned year-month, from MIN_YEAR to MAX_YEAR 706 * @return a {@code YearMonth} based on this year-month with the requested year, not null 707 * @throws DateTimeException if the year value is invalid 708 */ 709 public YearMonth withYear(int year) { 710 YEAR.checkValidValue(year); 711 return with(year, month); 712 } 713 714 /** 715 * Returns a copy of this {@code YearMonth} with the month-of-year altered. 716 * <p> 717 * This instance is immutable and unaffected by this method call. 718 * 719 * @param month the month-of-year to set in the returned year-month, from 1 (January) to 12 (December) 720 * @return a {@code YearMonth} based on this year-month with the requested month, not null 721 * @throws DateTimeException if the month-of-year value is invalid 722 */ 723 public YearMonth withMonth(int month) { 724 MONTH_OF_YEAR.checkValidValue(month); 725 return with(year, month); 726 } 727 728 //----------------------------------------------------------------------- 729 /** 730 * Returns a copy of this year-month with the specified amount added. 731 * <p> 732 * This returns a {@code YearMonth}, based on this one, with the specified amount added. 733 * The amount is typically {@link Period} but may be any other type implementing 734 * the {@link TemporalAmount} interface. 735 * <p> 736 * The calculation is delegated to the amount object by calling 737 * {@link TemporalAmount#addTo(Temporal)}. The amount implementation is free 738 * to implement the addition in any way it wishes, however it typically 739 * calls back to {@link #plus(long, TemporalUnit)}. Consult the documentation 740 * of the amount implementation to determine if it can be successfully added. 741 * <p> 742 * This instance is immutable and unaffected by this method call. 743 * 744 * @param amountToAdd the amount to add, not null 745 * @return a {@code YearMonth} based on this year-month with the addition made, not null 746 * @throws DateTimeException if the addition cannot be made 747 * @throws ArithmeticException if numeric overflow occurs 748 */ 749 @Override 750 public YearMonth plus(TemporalAmount amountToAdd) { 751 return (YearMonth) amountToAdd.addTo(this); 752 } 753 754 /** 755 * Returns a copy of this year-month with the specified amount added. 756 * <p> 757 * This returns a {@code YearMonth}, based on this one, with the amount 758 * in terms of the unit added. If it is not possible to add the amount, because the 759 * unit is not supported or for some other reason, an exception is thrown. 760 * <p> 761 * If the field is a {@link ChronoUnit} then the addition is implemented here. 762 * The supported fields behave as follows: 763 * <ul> 764 * <li>{@code MONTHS} - 765 * Returns a {@code YearMonth} with the specified number of months added. 766 * This is equivalent to {@link #plusMonths(long)}. 767 * <li>{@code YEARS} - 768 * Returns a {@code YearMonth} with the specified number of years added. 769 * This is equivalent to {@link #plusYears(long)}. 770 * <li>{@code DECADES} - 771 * Returns a {@code YearMonth} with the specified number of decades added. 772 * This is equivalent to calling {@link #plusYears(long)} with the amount 773 * multiplied by 10. 774 * <li>{@code CENTURIES} - 775 * Returns a {@code YearMonth} with the specified number of centuries added. 776 * This is equivalent to calling {@link #plusYears(long)} with the amount 777 * multiplied by 100. 778 * <li>{@code MILLENNIA} - 779 * Returns a {@code YearMonth} with the specified number of millennia added. 780 * This is equivalent to calling {@link #plusYears(long)} with the amount 781 * multiplied by 1,000. 782 * <li>{@code ERAS} - 783 * Returns a {@code YearMonth} with the specified number of eras added. 784 * Only two eras are supported so the amount must be one, zero or minus one. 785 * If the amount is non-zero then the year is changed such that the year-of-era 786 * is unchanged. 787 * </ul> 788 * <p> 789 * All other {@code ChronoUnit} instances will throw an {@code UnsupportedTemporalTypeException}. 790 * <p> 791 * If the field is not a {@code ChronoUnit}, then the result of this method 792 * is obtained by invoking {@code TemporalUnit.addTo(Temporal, long)} 793 * passing {@code this} as the argument. In this case, the unit determines 794 * whether and how to perform the addition. 795 * <p> 796 * This instance is immutable and unaffected by this method call. 797 * 798 * @param amountToAdd the amount of the unit to add to the result, may be negative 799 * @param unit the unit of the amount to add, not null 800 * @return a {@code YearMonth} based on this year-month with the specified amount added, not null 801 * @throws DateTimeException if the addition cannot be made 802 * @throws UnsupportedTemporalTypeException if the unit is not supported 803 * @throws ArithmeticException if numeric overflow occurs 804 */ 805 @Override 806 public YearMonth plus(long amountToAdd, TemporalUnit unit) { 807 if (unit instanceof ChronoUnit) { 808 switch ((ChronoUnit) unit) { 809 case MONTHS: return plusMonths(amountToAdd); 810 case YEARS: return plusYears(amountToAdd); 811 case DECADES: return plusYears(Math.multiplyExact(amountToAdd, 10)); 812 case CENTURIES: return plusYears(Math.multiplyExact(amountToAdd, 100)); 813 case MILLENNIA: return plusYears(Math.multiplyExact(amountToAdd, 1000)); 814 case ERAS: return with(ERA, Math.addExact(getLong(ERA), amountToAdd)); 815 } 816 throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit); 817 } 818 return unit.addTo(this, amountToAdd); 819 } 820 821 /** 822 * Returns a copy of this {@code YearMonth} with the specified number of years added. 823 * <p> 824 * This instance is immutable and unaffected by this method call. 825 * 826 * @param yearsToAdd the years to add, may be negative 827 * @return a {@code YearMonth} based on this year-month with the years added, not null 828 * @throws DateTimeException if the result exceeds the supported range 829 */ 830 public YearMonth plusYears(long yearsToAdd) { 831 if (yearsToAdd == 0) { 832 return this; 833 } 834 int newYear = YEAR.checkValidIntValue(year + yearsToAdd); // safe overflow 835 return with(newYear, month); 836 } 837 838 /** 839 * Returns a copy of this {@code YearMonth} with the specified number of months added. 840 * <p> 841 * This instance is immutable and unaffected by this method call. 842 * 843 * @param monthsToAdd the months to add, may be negative 844 * @return a {@code YearMonth} based on this year-month with the months added, not null 845 * @throws DateTimeException if the result exceeds the supported range 846 */ 847 public YearMonth plusMonths(long monthsToAdd) { 848 if (monthsToAdd == 0) { 849 return this; 850 } 851 long monthCount = year * 12L + (month - 1); 852 long calcMonths = monthCount + monthsToAdd; // safe overflow 853 int newYear = YEAR.checkValidIntValue(Math.floorDiv(calcMonths, 12)); 854 int newMonth = Math.floorMod(calcMonths, 12) + 1; 855 return with(newYear, newMonth); 856 } 857 858 //----------------------------------------------------------------------- 859 /** 860 * Returns a copy of this year-month with the specified amount subtracted. 861 * <p> 862 * This returns a {@code YearMonth}, based on this one, with the specified amount subtracted. 863 * The amount is typically {@link Period} but may be any other type implementing 864 * the {@link TemporalAmount} interface. 865 * <p> 866 * The calculation is delegated to the amount object by calling 867 * {@link TemporalAmount#subtractFrom(Temporal)}. The amount implementation is free 868 * to implement the subtraction in any way it wishes, however it typically 869 * calls back to {@link #minus(long, TemporalUnit)}. Consult the documentation 870 * of the amount implementation to determine if it can be successfully subtracted. 871 * <p> 872 * This instance is immutable and unaffected by this method call. 873 * 874 * @param amountToSubtract the amount to subtract, not null 875 * @return a {@code YearMonth} based on this year-month with the subtraction made, not null 876 * @throws DateTimeException if the subtraction cannot be made 877 * @throws ArithmeticException if numeric overflow occurs 878 */ 879 @Override 880 public YearMonth minus(TemporalAmount amountToSubtract) { 881 return (YearMonth) amountToSubtract.subtractFrom(this); 882 } 883 884 /** 885 * Returns a copy of this year-month with the specified amount subtracted. 886 * <p> 887 * This returns a {@code YearMonth}, based on this one, with the amount 888 * in terms of the unit subtracted. If it is not possible to subtract the amount, 889 * because the unit is not supported or for some other reason, an exception is thrown. 890 * <p> 891 * This method is equivalent to {@link #plus(long, TemporalUnit)} with the amount negated. 892 * See that method for a full description of how addition, and thus subtraction, works. 893 * <p> 894 * This instance is immutable and unaffected by this method call. 895 * 896 * @param amountToSubtract the amount of the unit to subtract from the result, may be negative 897 * @param unit the unit of the amount to subtract, not null 898 * @return a {@code YearMonth} based on this year-month with the specified amount subtracted, not null 899 * @throws DateTimeException if the subtraction cannot be made 900 * @throws UnsupportedTemporalTypeException if the unit is not supported 901 * @throws ArithmeticException if numeric overflow occurs 902 */ 903 @Override 904 public YearMonth minus(long amountToSubtract, TemporalUnit unit) { 905 return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit)); 906 } 907 908 /** 909 * Returns a copy of this {@code YearMonth} with the specified number of years subtracted. 910 * <p> 911 * This instance is immutable and unaffected by this method call. 912 * 913 * @param yearsToSubtract the years to subtract, may be negative 914 * @return a {@code YearMonth} based on this year-month with the years subtracted, not null 915 * @throws DateTimeException if the result exceeds the supported range 916 */ 917 public YearMonth minusYears(long yearsToSubtract) { 918 return (yearsToSubtract == Long.MIN_VALUE ? plusYears(Long.MAX_VALUE).plusYears(1) : plusYears(-yearsToSubtract)); 919 } 920 921 /** 922 * Returns a copy of this {@code YearMonth} with the specified number of months subtracted. 923 * <p> 924 * This instance is immutable and unaffected by this method call. 925 * 926 * @param monthsToSubtract the months to subtract, may be negative 927 * @return a {@code YearMonth} based on this year-month with the months subtracted, not null 928 * @throws DateTimeException if the result exceeds the supported range 929 */ 930 public YearMonth minusMonths(long monthsToSubtract) { 931 return (monthsToSubtract == Long.MIN_VALUE ? plusMonths(Long.MAX_VALUE).plusMonths(1) : plusMonths(-monthsToSubtract)); 932 } 933 934 //----------------------------------------------------------------------- 935 /** 936 * Queries this year-month using the specified query. 937 * <p> 938 * This queries this year-month using the specified query strategy object. 939 * The {@code TemporalQuery} object defines the logic to be used to 940 * obtain the result. Read the documentation of the query to understand 941 * what the result of this method will be. 942 * <p> 943 * The result of this method is obtained by invoking the 944 * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the 945 * specified query passing {@code this} as the argument. 946 * 947 * @param <R> the type of the result 948 * @param query the query to invoke, not null 949 * @return the query result, null may be returned (defined by the query) 950 * @throws DateTimeException if unable to query (defined by the query) 951 * @throws ArithmeticException if numeric overflow occurs (defined by the query) 952 */ 953 @SuppressWarnings("unchecked") 954 @Override 955 public <R> R query(TemporalQuery<R> query) { 956 if (query == TemporalQueries.chronology()) { 957 return (R) IsoChronology.INSTANCE; 958 } else if (query == TemporalQueries.precision()) { 959 return (R) MONTHS; 960 } 961 return Temporal.super.query(query); 962 } 963 964 /** 965 * Adjusts the specified temporal object to have this year-month. 966 * <p> 967 * This returns a temporal object of the same observable type as the input 968 * with the year and month changed to be the same as this. 969 * <p> 970 * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)} 971 * passing {@link ChronoField#PROLEPTIC_MONTH} as the field. 972 * If the specified temporal object does not use the ISO calendar system then 973 * a {@code DateTimeException} is thrown. 974 * <p> 975 * In most cases, it is clearer to reverse the calling pattern by using 976 * {@link Temporal#with(TemporalAdjuster)}: 977 * <pre> 978 * // these two lines are equivalent, but the second approach is recommended 979 * temporal = thisYearMonth.adjustInto(temporal); 980 * temporal = temporal.with(thisYearMonth); 981 * </pre> 982 * <p> 983 * This instance is immutable and unaffected by this method call. 984 * 985 * @param temporal the target object to be adjusted, not null 986 * @return the adjusted object, not null 987 * @throws DateTimeException if unable to make the adjustment 988 * @throws ArithmeticException if numeric overflow occurs 989 */ 990 @Override 991 public Temporal adjustInto(Temporal temporal) { 992 if (Chronology.from(temporal).equals(IsoChronology.INSTANCE) == false) { 993 throw new DateTimeException("Adjustment only supported on ISO date-time"); 994 } 995 return temporal.with(PROLEPTIC_MONTH, getProlepticMonth()); 996 } 997 998 /** 999 * Calculates the amount of time until another year-month in terms of the specified unit. 1000 * <p> 1001 * This calculates the amount of time between two {@code YearMonth} 1002 * objects in terms of a single {@code TemporalUnit}. 1003 * The start and end points are {@code this} and the specified year-month. 1004 * The result will be negative if the end is before the start. 1005 * The {@code Temporal} passed to this method is converted to a 1006 * {@code YearMonth} using {@link #from(TemporalAccessor)}. 1007 * For example, the amount in years between two year-months can be calculated 1008 * using {@code startYearMonth.until(endYearMonth, YEARS)}. 1009 * <p> 1010 * The calculation returns a whole number, representing the number of 1011 * complete units between the two year-months. 1012 * For example, the amount in decades between 2012-06 and 2032-05 1013 * will only be one decade as it is one month short of two decades. 1014 * <p> 1015 * There are two equivalent ways of using this method. 1016 * The first is to invoke this method. 1017 * The second is to use {@link TemporalUnit#between(Temporal, Temporal)}: 1018 * <pre> 1019 * // these two lines are equivalent 1020 * amount = start.until(end, MONTHS); 1021 * amount = MONTHS.between(start, end); 1022 * </pre> 1023 * The choice should be made based on which makes the code more readable. 1024 * <p> 1025 * The calculation is implemented in this method for {@link ChronoUnit}. 1026 * The units {@code MONTHS}, {@code YEARS}, {@code DECADES}, 1027 * {@code CENTURIES}, {@code MILLENNIA} and {@code ERAS} are supported. 1028 * Other {@code ChronoUnit} values will throw an exception. 1029 * <p> 1030 * If the unit is not a {@code ChronoUnit}, then the result of this method 1031 * is obtained by invoking {@code TemporalUnit.between(Temporal, Temporal)} 1032 * passing {@code this} as the first argument and the converted input temporal 1033 * as the second argument. 1034 * <p> 1035 * This instance is immutable and unaffected by this method call. 1036 * 1037 * @param endExclusive the end date, exclusive, which is converted to a {@code YearMonth}, not null 1038 * @param unit the unit to measure the amount in, not null 1039 * @return the amount of time between this year-month and the end year-month 1040 * @throws DateTimeException if the amount cannot be calculated, or the end 1041 * temporal cannot be converted to a {@code YearMonth} 1042 * @throws UnsupportedTemporalTypeException if the unit is not supported 1043 * @throws ArithmeticException if numeric overflow occurs 1044 */ 1045 @Override 1046 public long until(Temporal endExclusive, TemporalUnit unit) { 1047 YearMonth end = YearMonth.from(endExclusive); 1048 if (unit instanceof ChronoUnit) { 1049 long monthsUntil = end.getProlepticMonth() - getProlepticMonth(); // no overflow 1050 switch ((ChronoUnit) unit) { 1051 case MONTHS: return monthsUntil; 1052 case YEARS: return monthsUntil / 12; 1053 case DECADES: return monthsUntil / 120; 1054 case CENTURIES: return monthsUntil / 1200; 1055 case MILLENNIA: return monthsUntil / 12000; 1056 case ERAS: return end.getLong(ERA) - getLong(ERA); 1057 } 1058 throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit); 1059 } 1060 return unit.between(this, end); 1061 } 1062 1063 /** 1064 * Formats this year-month using the specified formatter. 1065 * <p> 1066 * This year-month will be passed to the formatter to produce a string. 1067 * 1068 * @param formatter the formatter to use, not null 1069 * @return the formatted year-month string, not null 1070 * @throws DateTimeException if an error occurs during printing 1071 */ 1072 public String format(DateTimeFormatter formatter) { 1073 Objects.requireNonNull(formatter, "formatter"); 1074 return formatter.format(this); 1075 } 1076 1077 //----------------------------------------------------------------------- 1078 /** 1079 * Combines this year-month with a day-of-month to create a {@code LocalDate}. 1080 * <p> 1081 * This returns a {@code LocalDate} formed from this year-month and the specified day-of-month. 1082 * <p> 1083 * The day-of-month value must be valid for the year-month. 1084 * <p> 1085 * This method can be used as part of a chain to produce a date: 1086 * <pre> 1087 * LocalDate date = year.atMonth(month).atDay(day); 1088 * </pre> 1089 * 1090 * @param dayOfMonth the day-of-month to use, from 1 to 31 1091 * @return the date formed from this year-month and the specified day, not null 1092 * @throws DateTimeException if the day is invalid for the year-month 1093 * @see #isValidDay(int) 1094 */ 1095 public LocalDate atDay(int dayOfMonth) { 1096 return LocalDate.of(year, month, dayOfMonth); 1097 } 1098 1099 /** 1100 * Returns a {@code LocalDate} at the end of the month. 1101 * <p> 1102 * This returns a {@code LocalDate} based on this year-month. 1103 * The day-of-month is set to the last valid day of the month, taking 1104 * into account leap years. 1105 * <p> 1106 * This method can be used as part of a chain to produce a date: 1107 * <pre> 1108 * LocalDate date = year.atMonth(month).atEndOfMonth(); 1109 * </pre> 1110 * 1111 * @return the last valid date of this year-month, not null 1112 */ 1113 public LocalDate atEndOfMonth() { 1114 return LocalDate.of(year, month, lengthOfMonth()); 1115 } 1116 1117 //----------------------------------------------------------------------- 1118 /** 1119 * Compares this year-month to another year-month. 1120 * <p> 1121 * The comparison is based first on the value of the year, then on the value of the month. 1122 * It is "consistent with equals", as defined by {@link Comparable}. 1123 * 1124 * @param other the other year-month to compare to, not null 1125 * @return the comparator value, negative if less, positive if greater 1126 */ 1127 @Override 1128 public int compareTo(YearMonth other) { 1129 int cmp = (year - other.year); 1130 if (cmp == 0) { 1131 cmp = (month - other.month); 1132 } 1133 return cmp; 1134 } 1135 1136 /** 1137 * Checks if this year-month is after the specified year-month. 1138 * 1139 * @param other the other year-month to compare to, not null 1140 * @return true if this is after the specified year-month 1141 */ 1142 public boolean isAfter(YearMonth other) { 1143 return compareTo(other) > 0; 1144 } 1145 1146 /** 1147 * Checks if this year-month is before the specified year-month. 1148 * 1149 * @param other the other year-month to compare to, not null 1150 * @return true if this point is before the specified year-month 1151 */ 1152 public boolean isBefore(YearMonth other) { 1153 return compareTo(other) < 0; 1154 } 1155 1156 //----------------------------------------------------------------------- 1157 /** 1158 * Checks if this year-month is equal to another year-month. 1159 * <p> 1160 * The comparison is based on the time-line position of the year-months. 1161 * 1162 * @param obj the object to check, null returns false 1163 * @return true if this is equal to the other year-month 1164 */ 1165 @Override 1166 public boolean equals(Object obj) { 1167 if (this == obj) { 1168 return true; 1169 } 1170 if (obj instanceof YearMonth) { 1171 YearMonth other = (YearMonth) obj; 1172 return year == other.year && month == other.month; 1173 } 1174 return false; 1175 } 1176 1177 /** 1178 * A hash code for this year-month. 1179 * 1180 * @return a suitable hash code 1181 */ 1182 @Override 1183 public int hashCode() { 1184 return year ^ (month << 27); 1185 } 1186 1187 //----------------------------------------------------------------------- 1188 /** 1189 * Outputs this year-month as a {@code String}, such as {@code 2007-12}. 1190 * <p> 1191 * The output will be in the format {@code uuuu-MM}: 1192 * 1193 * @return a string representation of this year-month, not null 1194 */ 1195 @Override 1196 public String toString() { 1197 int absYear = Math.abs(year); 1198 StringBuilder buf = new StringBuilder(9); 1199 if (absYear < 1000) { 1200 if (year < 0) { 1201 buf.append(year - 10000).deleteCharAt(1); 1202 } else { 1203 buf.append(year + 10000).deleteCharAt(0); 1204 } 1205 } else { 1206 buf.append(year); 1207 } 1208 return buf.append(month < 10 ? "-0" : "-") 1209 .append(month) 1210 .toString(); 1211 } 1212 1213 //----------------------------------------------------------------------- 1214 /** 1215 * Writes the object using a 1216 * <a href="{@docRoot}/serialized-form.html#java.time.Ser">dedicated serialized form</a>. 1217 * @serialData 1218 * <pre> 1219 * out.writeByte(12); // identifies a YearMonth 1220 * out.writeInt(year); 1221 * out.writeByte(month); 1222 * </pre> 1223 * 1224 * @return the instance of {@code Ser}, not null 1225 */ 1226 @java.io.Serial 1227 private Object writeReplace() { 1228 return new Ser(Ser.YEAR_MONTH_TYPE, this); 1229 } 1230 1231 /** 1232 * Defend against malicious streams. 1233 * 1234 * @param s the stream to read 1235 * @throws InvalidObjectException always 1236 */ 1237 @java.io.Serial 1238 private void readObject(ObjectInputStream s) throws InvalidObjectException { 1239 throw new InvalidObjectException("Deserialization via serialization delegate"); 1240 } 1241 1242 void writeExternal(DataOutput out) throws IOException { 1243 out.writeInt(year); 1244 out.writeByte(month); 1245 } 1246 1247 static YearMonth readExternal(DataInput in) throws IOException { 1248 int year = in.readInt(); 1249 byte month = in.readByte(); 1250 return YearMonth.of(year, month); 1251 } 1252 1253 }