1 /*

     2  * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.

     3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

     4  *

     5  * This code is free software; you can redistribute it and/or modify it

     6  * under the terms of the GNU General Public License version 2 only, as

     7  * published by the Free Software Foundation.  Oracle designates this

     8  * particular file as subject to the "Classpath" exception as provided

     9  * by Oracle in the LICENSE file that accompanied this code.

    10  *

    11  * This code is distributed in the hope that it will be useful, but WITHOUT

    12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

    13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

    14  * version 2 for more details (a copy is included in the LICENSE file that

    15  * accompanied this code).

    16  *

    17  * You should have received a copy of the GNU General Public License version

    18  * 2 along with this work; if not, write to the Free Software Foundation,

    19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

    20  *

    21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 

    26 /*

    27  * This file is available under and governed by the GNU General Public

    28  * License version 2 only, as published by the Free Software Foundation.

    29  * However, the following notice accompanied the original version of this

    30  * file:

    31  *

    32  * Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos

    33  *

    34  * All rights reserved.

    35  *

    36  * Redistribution and use in source and binary forms, with or without

    37  * modification, are permitted provided that the following conditions are met:

    38  *

    39  *  * Redistributions of source code must retain the above copyright notice,

    40  *    this list of conditions and the following disclaimer.

    41  *

    42  *  * Redistributions in binary form must reproduce the above copyright notice,

    43  *    this list of conditions and the following disclaimer in the documentation

    44  *    and/or other materials provided with the distribution.

    45  *

    46  *  * Neither the name of JSR-310 nor the names of its contributors

    47  *    may be used to endorse or promote products derived from this software

    48  *    without specific prior written permission.

    49  *

    50  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS

    51  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

    52  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR

    53  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR

    54  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

    55  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

    56  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

    57  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF

    58  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING

    59  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

    60  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

    61  */

    62 package java.time;

    63 

    64 import static java.time.temporal.ChronoField.OFFSET_SECONDS;

    65 

    66 import java.io.DataInput;

    67 import java.io.DataOutput;

    68 import java.io.IOException;

    69 import java.io.InvalidObjectException;

    70 import java.io.ObjectStreamException;

    71 import java.io.Serializable;

    72 import java.time.temporal.ChronoField;

    73 import java.time.temporal.Queries;

    74 import java.time.temporal.Temporal;

    75 import java.time.temporal.TemporalAccessor;

    76 import java.time.temporal.TemporalAdjuster;

    77 import java.time.temporal.TemporalField;

    78 import java.time.temporal.TemporalQuery;

    79 import java.time.temporal.ValueRange;

    80 import java.time.zone.ZoneRules;

    81 import java.util.Objects;

    82 import java.util.concurrent.ConcurrentHashMap;

    83 import java.util.concurrent.ConcurrentMap;

    84 

    85 /**

    86  * A time-zone offset from Greenwich/UTC, such as {@code +02:00}.

    87  * <p>

    88  * A time-zone offset is the period of time that a time-zone differs from Greenwich/UTC.

    89  * This is usually a fixed number of hours and minutes.

    90  * <p>

    91  * Different parts of the world have different time-zone offsets.

    92  * The rules for how offsets vary by place and time of year are captured in the

    93  * {@link ZoneId} class.

    94  * <p>

    95  * For example, Paris is one hour ahead of Greenwich/UTC in winter and two hours

    96  * ahead in summer. The {@code ZoneId} instance for Paris will reference two

    97  * {@code ZoneOffset} instances - a {@code +01:00} instance for winter,

    98  * and a {@code +02:00} instance for summer.

    99  * <p>

   100  * In 2008, time-zone offsets around the world extended from -12:00 to +14:00.

   101  * To prevent any problems with that range being extended, yet still provide

   102  * validation, the range of offsets is restricted to -18:00 to 18:00 inclusive.

   103  * <p>

   104  * This class is designed for use with the ISO calendar system.

   105  * The fields of hours, minutes and seconds make assumptions that are valid for the

   106  * standard ISO definitions of those fields. This class may be used with other

   107  * calendar systems providing the definition of the time fields matches those

   108  * of the ISO calendar system.

   109  * <p>

   110  * Instances of {@code ZoneOffset} must be compared using {@link #equals}.

   111  * Implementations may choose to cache certain common offsets, however

   112  * applications must not rely on such caching.

   113  *

   114  * <h3>Specification for implementors</h3>

   115  * This class is immutable and thread-safe.

   116  *

   117  * @since 1.8

   118  */

   119 public final class ZoneOffset

   120         extends ZoneId

   121         implements TemporalAccessor, TemporalAdjuster, Comparable<ZoneOffset>, Serializable {

   122 

   123     /** Cache of time-zone offset by offset in seconds. */

   124     private static final ConcurrentMap<Integer, ZoneOffset> SECONDS_CACHE = new ConcurrentHashMap<>(16, 0.75f, 4);

   125     /** Cache of time-zone offset by ID. */

   126     private static final ConcurrentMap<String, ZoneOffset> ID_CACHE = new ConcurrentHashMap<>(16, 0.75f, 4);

   127 

   128     /**

   129      * The number of seconds per hour.

   130      */

   131     private static final int SECONDS_PER_HOUR = 60 * 60;

   132     /**

   133      * The number of seconds per minute.

   134      */

   135     private static final int SECONDS_PER_MINUTE = 60;

   136     /**

   137      * The number of minutes per hour.

   138      */

   139     private static final int MINUTES_PER_HOUR = 60;

   140     /**

   141      * The abs maximum seconds.

   142      */

   143     private static final int MAX_SECONDS = 18 * SECONDS_PER_HOUR;

   144     /**

   145      * Serialization version.

   146      */

   147     private static final long serialVersionUID = 2357656521762053153L;

   148 

   149     /**

   150      * The time-zone offset for UTC, with an ID of 'Z'.

   151      */

   152     public static final ZoneOffset UTC = ZoneOffset.ofTotalSeconds(0);

   153     /**

   154      * Constant for the maximum supported offset.

   155      */

   156     public static final ZoneOffset MIN = ZoneOffset.ofTotalSeconds(-MAX_SECONDS);

   157     /**

   158      * Constant for the maximum supported offset.

   159      */

   160     public static final ZoneOffset MAX = ZoneOffset.ofTotalSeconds(MAX_SECONDS);

   161 

   162     /**

   163      * The total offset in seconds.

   164      */

   165     private final int totalSeconds;

   166     /**

   167      * The string form of the time-zone offset.

   168      */

   169     private final transient String id;

   170 

   171     //-----------------------------------------------------------------------

   172     /**

   173      * Obtains an instance of {@code ZoneOffset} using the ID.

   174      * <p>

   175      * This method parses the string ID of a {@code ZoneOffset} to

   176      * return an instance. The parsing accepts all the formats generated by

   177      * {@link #getId()}, plus some additional formats:

   178      * <p><ul>

   179      * <li>{@code Z} - for UTC

   180      * <li>{@code +h}

   181      * <li>{@code +hh}

   182      * <li>{@code +hh:mm}

   183      * <li>{@code -hh:mm}

   184      * <li>{@code +hhmm}

   185      * <li>{@code -hhmm}

   186      * <li>{@code +hh:mm:ss}

   187      * <li>{@code -hh:mm:ss}

   188      * <li>{@code +hhmmss}

   189      * <li>{@code -hhmmss}

   190      * </ul><p>

   191      * Note that ± means either the plus or minus symbol.

   192      * <p>

   193      * The ID of the returned offset will be normalized to one of the formats

   194      * described by {@link #getId()}.

   195      * <p>

   196      * The maximum supported range is from +18:00 to -18:00 inclusive.

   197      *

   198      * @param offsetId  the offset ID, not null

   199      * @return the zone-offset, not null

   200      * @throws DateTimeException if the offset ID is invalid

   201      */

   202     @SuppressWarnings("fallthrough")

   203     public static ZoneOffset of(String offsetId) {

   204         Objects.requireNonNull(offsetId, "offsetId");

   205         // "Z" is always in the cache

   206         ZoneOffset offset = ID_CACHE.get(offsetId);

   207         if (offset != null) {

   208             return offset;

   209         }

   210 

   211         // parse - +h, +hh, +hhmm, +hh:mm, +hhmmss, +hh:mm:ss

   212         final int hours, minutes, seconds;

   213         switch (offsetId.length()) {

   214             case 2:

   215                 offsetId = offsetId.charAt(0) + "0" + offsetId.charAt(1);  // fallthru

   216             case 3:

   217                 hours = parseNumber(offsetId, 1, false);

   218                 minutes = 0;

   219                 seconds = 0;

   220                 break;

   221             case 5:

   222                 hours = parseNumber(offsetId, 1, false);

   223                 minutes = parseNumber(offsetId, 3, false);

   224                 seconds = 0;

   225                 break;

   226             case 6:

   227                 hours = parseNumber(offsetId, 1, false);

   228                 minutes = parseNumber(offsetId, 4, true);

   229                 seconds = 0;

   230                 break;

   231             case 7:

   232                 hours = parseNumber(offsetId, 1, false);

   233                 minutes = parseNumber(offsetId, 3, false);

   234                 seconds = parseNumber(offsetId, 5, false);

   235                 break;

   236             case 9:

   237                 hours = parseNumber(offsetId, 1, false);

   238                 minutes = parseNumber(offsetId, 4, true);

   239                 seconds = parseNumber(offsetId, 7, true);

   240                 break;

   241             default:

   242                 throw new DateTimeException("Zone offset ID '" + offsetId + "' is invalid");

   243         }

   244         char first = offsetId.charAt(0);

   245         if (first != '+' && first != '-') {

   246             throw new DateTimeException("Zone offset ID '" + offsetId + "' is invalid: Plus/minus not found when expected");

   247         }

   248         if (first == '-') {

   249             return ofHoursMinutesSeconds(-hours, -minutes, -seconds);

   250         } else {

   251             return ofHoursMinutesSeconds(hours, minutes, seconds);

   252         }

   253     }

   254 

   255     /**

   256      * Parse a two digit zero-prefixed number.

   257      *

   258      * @param offsetId  the offset ID, not null

   259      * @param pos  the position to parse, valid

   260      * @param precededByColon  should this number be prefixed by a precededByColon

   261      * @return the parsed number, from 0 to 99

   262      */

   263     private static int parseNumber(CharSequence offsetId, int pos, boolean precededByColon) {

   264         if (precededByColon && offsetId.charAt(pos - 1) != ':') {

   265             throw new DateTimeException("Zone offset ID '" + offsetId + "' is invalid: Colon not found when expected");

   266         }

   267         char ch1 = offsetId.charAt(pos);

   268         char ch2 = offsetId.charAt(pos + 1);

   269         if (ch1 < '0' || ch1 > '9' || ch2 < '0' || ch2 > '9') {

   270             throw new DateTimeException("Zone offset ID '" + offsetId + "' is invalid: Non numeric characters found");

   271         }

   272         return (ch1 - 48) * 10 + (ch2 - 48);

   273     }

   274 

   275     //-----------------------------------------------------------------------

   276     /**

   277      * Obtains an instance of {@code ZoneOffset} using an offset in hours.

   278      *

   279      * @param hours  the time-zone offset in hours, from -18 to +18

   280      * @return the zone-offset, not null

   281      * @throws DateTimeException if the offset is not in the required range

   282      */

   283     public static ZoneOffset ofHours(int hours) {

   284         return ofHoursMinutesSeconds(hours, 0, 0);

   285     }

   286 

   287     /**

   288      * Obtains an instance of {@code ZoneOffset} using an offset in

   289      * hours and minutes.

   290      * <p>

   291      * The sign of the hours and minutes components must match.

   292      * Thus, if the hours is negative, the minutes must be negative or zero.

   293      * If the hours is zero, the minutes may be positive, negative or zero.

   294      *

   295      * @param hours  the time-zone offset in hours, from -18 to +18

   296      * @param minutes  the time-zone offset in minutes, from 0 to ±59, sign matches hours

   297      * @return the zone-offset, not null

   298      * @throws DateTimeException if the offset is not in the required range

   299      */

   300     public static ZoneOffset ofHoursMinutes(int hours, int minutes) {

   301         return ofHoursMinutesSeconds(hours, minutes, 0);

   302     }

   303 

   304     /**

   305      * Obtains an instance of {@code ZoneOffset} using an offset in

   306      * hours, minutes and seconds.

   307      * <p>

   308      * The sign of the hours, minutes and seconds components must match.

   309      * Thus, if the hours is negative, the minutes and seconds must be negative or zero.

   310      *

   311      * @param hours  the time-zone offset in hours, from -18 to +18

   312      * @param minutes  the time-zone offset in minutes, from 0 to ±59, sign matches hours and seconds

   313      * @param seconds  the time-zone offset in seconds, from 0 to ±59, sign matches hours and minutes

   314      * @return the zone-offset, not null

   315      * @throws DateTimeException if the offset is not in the required range

   316      */

   317     public static ZoneOffset ofHoursMinutesSeconds(int hours, int minutes, int seconds) {

   318         validate(hours, minutes, seconds);

   319         int totalSeconds = totalSeconds(hours, minutes, seconds);

   320         return ofTotalSeconds(totalSeconds);

   321     }

   322 

   323     //-----------------------------------------------------------------------

   324     /**

   325      * Obtains an instance of {@code ZoneOffset} from a temporal object.

   326      * <p>

   327      * A {@code TemporalAccessor} represents some form of date and time information.

   328      * This factory converts the arbitrary temporal object to an instance of {@code ZoneOffset}.

   329      * <p>

   330      * The conversion extracts the {@link ChronoField#OFFSET_SECONDS offset-seconds} field.

   331      * <p>

   332      * This method matches the signature of the functional interface {@link TemporalQuery}

   333      * allowing it to be used in queries via method reference, {@code ZoneOffset::from}.

   334      *

   335      * @param temporal  the temporal object to convert, not null

   336      * @return the zone-offset, not null

   337      * @throws DateTimeException if unable to convert to an {@code ZoneOffset}

   338      */

   339     public static ZoneOffset from(TemporalAccessor temporal) {

   340         if (temporal instanceof ZoneOffset) {

   341             return (ZoneOffset) temporal;

   342         }

   343         try {

   344             return ofTotalSeconds(temporal.get(OFFSET_SECONDS));

   345         } catch (DateTimeException ex) {

   346             throw new DateTimeException("Unable to obtain ZoneOffset from TemporalAccessor: " + temporal.getClass(), ex);

   347         }

   348     }

   349 

   350     //-----------------------------------------------------------------------

   351     /**

   352      * Validates the offset fields.

   353      *

   354      * @param hours  the time-zone offset in hours, from -18 to +18

   355      * @param minutes  the time-zone offset in minutes, from 0 to ±59

   356      * @param seconds  the time-zone offset in seconds, from 0 to ±59

   357      * @throws DateTimeException if the offset is not in the required range

   358      */

   359     private static void validate(int hours, int minutes, int seconds) {

   360         if (hours < -18 || hours > 18) {

   361             throw new DateTimeException("Zone offset hours not in valid range: value " + hours +

   362                     " is not in the range -18 to 18");

   363         }

   364         if (hours > 0) {

   365             if (minutes < 0 || seconds < 0) {

   366                 throw new DateTimeException("Zone offset minutes and seconds must be positive because hours is positive");

   367             }

   368         } else if (hours < 0) {

   369             if (minutes > 0 || seconds > 0) {

   370                 throw new DateTimeException("Zone offset minutes and seconds must be negative because hours is negative");

   371             }

   372         } else if ((minutes > 0 && seconds < 0) || (minutes < 0 && seconds > 0)) {

   373             throw new DateTimeException("Zone offset minutes and seconds must have the same sign");

   374         }

   375         if (Math.abs(minutes) > 59) {

   376             throw new DateTimeException("Zone offset minutes not in valid range: abs(value) " +

   377                     Math.abs(minutes) + " is not in the range 0 to 59");

   378         }

   379         if (Math.abs(seconds) > 59) {

   380             throw new DateTimeException("Zone offset seconds not in valid range: abs(value) " +

   381                     Math.abs(seconds) + " is not in the range 0 to 59");

   382         }

   383         if (Math.abs(hours) == 18 && (Math.abs(minutes) > 0 || Math.abs(seconds) > 0)) {

   384             throw new DateTimeException("Zone offset not in valid range: -18:00 to +18:00");

   385         }

   386     }

   387 

   388     /**

   389      * Calculates the total offset in seconds.

   390      *

   391      * @param hours  the time-zone offset in hours, from -18 to +18

   392      * @param minutes  the time-zone offset in minutes, from 0 to ±59, sign matches hours and seconds

   393      * @param seconds  the time-zone offset in seconds, from 0 to ±59, sign matches hours and minutes

   394      * @return the total in seconds

   395      */

   396     private static int totalSeconds(int hours, int minutes, int seconds) {

   397         return hours * SECONDS_PER_HOUR + minutes * SECONDS_PER_MINUTE + seconds;

   398     }

   399 

   400     //-----------------------------------------------------------------------

   401     /**

   402      * Obtains an instance of {@code ZoneOffset} specifying the total offset in seconds

   403      * <p>

   404      * The offset must be in the range {@code -18:00} to {@code +18:00}, which corresponds to -64800 to +64800.

   405      *

   406      * @param totalSeconds  the total time-zone offset in seconds, from -64800 to +64800

   407      * @return the ZoneOffset, not null

   408      * @throws DateTimeException if the offset is not in the required range

   409      */

   410     public static ZoneOffset ofTotalSeconds(int totalSeconds) {

   411         if (Math.abs(totalSeconds) > MAX_SECONDS) {

   412             throw new DateTimeException("Zone offset not in valid range: -18:00 to +18:00");

   413         }

   414         if (totalSeconds % (15 * SECONDS_PER_MINUTE) == 0) {

   415             Integer totalSecs = totalSeconds;

   416             ZoneOffset result = SECONDS_CACHE.get(totalSecs);

   417             if (result == null) {

   418                 result = new ZoneOffset(totalSeconds);

   419                 SECONDS_CACHE.putIfAbsent(totalSecs, result);

   420                 result = SECONDS_CACHE.get(totalSecs);

   421                 ID_CACHE.putIfAbsent(result.getId(), result);

   422             }

   423             return result;

   424         } else {

   425             return new ZoneOffset(totalSeconds);

   426         }

   427     }

   428 

   429     //-----------------------------------------------------------------------

   430     /**

   431      * Constructor.

   432      *

   433      * @param totalSeconds  the total time-zone offset in seconds, from -64800 to +64800

   434      */

   435     private ZoneOffset(int totalSeconds) {

   436         super();

   437         this.totalSeconds = totalSeconds;

   438         id = buildId(totalSeconds);

   439     }

   440 

   441     private static String buildId(int totalSeconds) {

   442         if (totalSeconds == 0) {

   443             return "Z";

   444         } else {

   445             int absTotalSeconds = Math.abs(totalSeconds);

   446             StringBuilder buf = new StringBuilder();

   447             int absHours = absTotalSeconds / SECONDS_PER_HOUR;

   448             int absMinutes = (absTotalSeconds / SECONDS_PER_MINUTE) % MINUTES_PER_HOUR;

   449             buf.append(totalSeconds < 0 ? "-" : "+")

   450                 .append(absHours < 10 ? "0" : "").append(absHours)

   451                 .append(absMinutes < 10 ? ":0" : ":").append(absMinutes);

   452             int absSeconds = absTotalSeconds % SECONDS_PER_MINUTE;

   453             if (absSeconds != 0) {

   454                 buf.append(absSeconds < 10 ? ":0" : ":").append(absSeconds);

   455             }

   456             return buf.toString();

   457         }

   458     }

   459 

   460     //-----------------------------------------------------------------------

   461     /**

   462      * Gets the total zone offset in seconds.

   463      * <p>

   464      * This is the primary way to access the offset amount.

   465      * It returns the total of the hours, minutes and seconds fields as a

   466      * single offset that can be added to a time.

   467      *

   468      * @return the total zone offset amount in seconds

   469      */

   470     public int getTotalSeconds() {

   471         return totalSeconds;

   472     }

   473 

   474     /**

   475      * Gets the normalized zone offset ID.

   476      * <p>

   477      * The ID is minor variation to the standard ISO-8601 formatted string

   478      * for the offset. There are three formats:

   479      * <p><ul>

   480      * <li>{@code Z} - for UTC (ISO-8601)

   481      * <li>{@code +hh:mm} or {@code -hh:mm} - if the seconds are zero (ISO-8601)

   482      * <li>{@code +hh:mm:ss} or {@code -hh:mm:ss} - if the seconds are non-zero (not ISO-8601)

   483      * </ul><p>

   484      *

   485      * @return the zone offset ID, not null

   486      */

   487     @Override

   488     public String getId() {

   489         return id;

   490     }

   491 

   492     /**

   493      * Gets the associated time-zone rules.

   494      * <p>

   495      * The rules will always return this offset when queried.

   496      * The implementation class is immutable, thread-safe and serializable.

   497      *

   498      * @return the rules, not null

   499      */

   500     @Override

   501     public ZoneRules getRules() {

   502         return ZoneRules.of(this);

   503     }

   504 

   505     //-----------------------------------------------------------------------

   506     /**

   507      * Checks if the specified field is supported.

   508      * <p>

   509      * This checks if this offset can be queried for the specified field.

   510      * If false, then calling the {@link #range(TemporalField) range} and

   511      * {@link #get(TemporalField) get} methods will throw an exception.

   512      * <p>

   513      * If the field is a {@link ChronoField} then the query is implemented here.

   514      * The {@code OFFSET_SECONDS} field returns true.

   515      * All other {@code ChronoField} instances will return false.

   516      * <p>

   517      * If the field is not a {@code ChronoField}, then the result of this method

   518      * is obtained by invoking {@code TemporalField.doIsSupported(TemporalAccessor)}

   519      * passing {@code this} as the argument.

   520      * Whether the field is supported is determined by the field.

   521      *

   522      * @param field  the field to check, null returns false

   523      * @return true if the field is supported on this offset, false if not

   524      */

   525     @Override

   526     public boolean isSupported(TemporalField field) {

   527         if (field instanceof ChronoField) {

   528             return field == OFFSET_SECONDS;

   529         }

   530         return field != null && field.doIsSupported(this);

   531     }

   532 

   533     /**

   534      * Gets the range of valid values for the specified field.

   535      * <p>

   536      * The range object expresses the minimum and maximum valid values for a field.

   537      * This offset is used to enhance the accuracy of the returned range.

   538      * If it is not possible to return the range, because the field is not supported

   539      * or for some other reason, an exception is thrown.

   540      * <p>

   541      * If the field is a {@link ChronoField} then the query is implemented here.

   542      * The {@link #isSupported(TemporalField) supported fields} will return

   543      * appropriate range instances.

   544      * All other {@code ChronoField} instances will throw a {@code DateTimeException}.

   545      * <p>

   546      * If the field is not a {@code ChronoField}, then the result of this method

   547      * is obtained by invoking {@code TemporalField.doRange(TemporalAccessor)}

   548      * passing {@code this} as the argument.

   549      * Whether the range can be obtained is determined by the field.

   550      *

   551      * @param field  the field to query the range for, not null

   552      * @return the range of valid values for the field, not null

   553      * @throws DateTimeException if the range for the field cannot be obtained

   554      */

   555     @Override  // override for Javadoc

   556     public ValueRange range(TemporalField field) {

   557         return TemporalAccessor.super.range(field);

   558     }

   559 

   560     /**

   561      * Gets the value of the specified field from this offset as an {@code int}.

   562      * <p>

   563      * This queries this offset for the value for the specified field.

   564      * The returned value will always be within the valid range of values for the field.

   565      * If it is not possible to return the value, because the field is not supported

   566      * or for some other reason, an exception is thrown.

   567      * <p>

   568      * If the field is a {@link ChronoField} then the query is implemented here.

   569      * The {@code OFFSET_SECONDS} field returns the value of the offset.

   570      * All other {@code ChronoField} instances will throw a {@code DateTimeException}.

   571      * <p>

   572      * If the field is not a {@code ChronoField}, then the result of this method

   573      * is obtained by invoking {@code TemporalField.doGet(TemporalAccessor)}

   574      * passing {@code this} as the argument. Whether the value can be obtained,

   575      * and what the value represents, is determined by the field.

   576      *

   577      * @param field  the field to get, not null

   578      * @return the value for the field

   579      * @throws DateTimeException if a value for the field cannot be obtained

   580      * @throws ArithmeticException if numeric overflow occurs

   581      */

   582     @Override  // override for Javadoc and performance

   583     public int get(TemporalField field) {

   584         if (field == OFFSET_SECONDS) {

   585             return totalSeconds;

   586         } else if (field instanceof ChronoField) {

   587             throw new DateTimeException("Unsupported field: " + field.getName());

   588         }

   589         return range(field).checkValidIntValue(getLong(field), field);

   590     }

   591 

   592     /**

   593      * Gets the value of the specified field from this offset as a {@code long}.

   594      * <p>

   595      * This queries this offset for the value for the specified field.

   596      * If it is not possible to return the value, because the field is not supported

   597      * or for some other reason, an exception is thrown.

   598      * <p>

   599      * If the field is a {@link ChronoField} then the query is implemented here.

   600      * The {@code OFFSET_SECONDS} field returns the value of the offset.

   601      * All other {@code ChronoField} instances will throw a {@code DateTimeException}.

   602      * <p>

   603      * If the field is not a {@code ChronoField}, then the result of this method

   604      * is obtained by invoking {@code TemporalField.doGet(TemporalAccessor)}

   605      * passing {@code this} as the argument. Whether the value can be obtained,

   606      * and what the value represents, is determined by the field.

   607      *

   608      * @param field  the field to get, not null

   609      * @return the value for the field

   610      * @throws DateTimeException if a value for the field cannot be obtained

   611      * @throws ArithmeticException if numeric overflow occurs

   612      */

   613     @Override

   614     public long getLong(TemporalField field) {

   615         if (field == OFFSET_SECONDS) {

   616             return totalSeconds;

   617         } else if (field instanceof ChronoField) {

   618             throw new DateTimeException("Unsupported field: " + field.getName());

   619         }

   620         return field.doGet(this);

   621     }

   622 

   623     //-----------------------------------------------------------------------

   624     /**

   625      * Queries this offset using the specified query.

   626      * <p>

   627      * This queries this offset using the specified query strategy object.

   628      * The {@code TemporalQuery} object defines the logic to be used to

   629      * obtain the result. Read the documentation of the query to understand

   630      * what the result of this method will be.

   631      * <p>

   632      * The result of this method is obtained by invoking the

   633      * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the

   634      * specified query passing {@code this} as the argument.

   635      *

   636      * @param <R> the type of the result

   637      * @param query  the query to invoke, not null

   638      * @return the query result, null may be returned (defined by the query)

   639      * @throws DateTimeException if unable to query (defined by the query)

   640      * @throws ArithmeticException if numeric overflow occurs (defined by the query)

   641      */

   642     @SuppressWarnings("unchecked")

   643     @Override

   644     public <R> R query(TemporalQuery<R> query) {

   645         if (query == Queries.offset() || query == Queries.zone()) {

   646             return (R) this;

   647         }

   648         return TemporalAccessor.super.query(query);

   649     }

   650 

   651     /**

   652      * Adjusts the specified temporal object to have the same offset as this object.

   653      * <p>

   654      * This returns a temporal object of the same observable type as the input

   655      * with the offset changed to be the same as this.

   656      * <p>

   657      * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)}

   658      * passing {@link ChronoField#OFFSET_SECONDS} as the field.

   659      * <p>

   660      * In most cases, it is clearer to reverse the calling pattern by using

   661      * {@link Temporal#with(TemporalAdjuster)}:

   662      * <pre>

   663      *   // these two lines are equivalent, but the second approach is recommended

   664      *   temporal = thisOffset.adjustInto(temporal);

   665      *   temporal = temporal.with(thisOffset);

   666      * </pre>

   667      * <p>

   668      * This instance is immutable and unaffected by this method call.

   669      *

   670      * @param temporal  the target object to be adjusted, not null

   671      * @return the adjusted object, not null

   672      * @throws DateTimeException if unable to make the adjustment

   673      * @throws ArithmeticException if numeric overflow occurs

   674      */

   675     @Override

   676     public Temporal adjustInto(Temporal temporal) {

   677         return temporal.with(OFFSET_SECONDS, totalSeconds);

   678     }

   679 

   680     //-----------------------------------------------------------------------

   681     /**

   682      * Compares this offset to another offset in descending order.

   683      * <p>

   684      * The offsets are compared in the order that they occur for the same time

   685      * of day around the world. Thus, an offset of {@code +10:00} comes before an

   686      * offset of {@code +09:00} and so on down to {@code -18:00}.

   687      * <p>

   688      * The comparison is "consistent with equals", as defined by {@link Comparable}.

   689      *

   690      * @param other  the other date to compare to, not null

   691      * @return the comparator value, negative if less, postive if greater

   692      * @throws NullPointerException if {@code other} is null

   693      */

   694     @Override

   695     public int compareTo(ZoneOffset other) {

   696         return other.totalSeconds - totalSeconds;

   697     }

   698 

   699     //-----------------------------------------------------------------------

   700     /**

   701      * Checks if this offset is equal to another offset.

   702      * <p>

   703      * The comparison is based on the amount of the offset in seconds.

   704      * This is equivalent to a comparison by ID.

   705      *

   706      * @param obj  the object to check, null returns false

   707      * @return true if this is equal to the other offset

   708      */

   709     @Override

   710     public boolean equals(Object obj) {

   711         if (this == obj) {

   712            return true;

   713         }

   714         if (obj instanceof ZoneOffset) {

   715             return totalSeconds == ((ZoneOffset) obj).totalSeconds;

   716         }

   717         return false;

   718     }

   719 

   720     /**

   721      * A hash code for this offset.

   722      *

   723      * @return a suitable hash code

   724      */

   725     @Override

   726     public int hashCode() {

   727         return totalSeconds;

   728     }

   729 

   730     //-----------------------------------------------------------------------

   731     /**

   732      * Outputs this offset as a {@code String}, using the normalized ID.

   733      *

   734      * @return a string representation of this offset, not null

   735      */

   736     @Override

   737     public String toString() {

   738         return id;

   739     }

   740 

   741     // -----------------------------------------------------------------------

   742     /**

   743      * Writes the object using a

   744      * <a href="../../serialized-form.html#java.time.Ser">dedicated serialized form</a>.

   745      * <pre>

   746      *  out.writeByte(8);  // identifies this as a ZoneOffset

   747      *  int offsetByte = totalSeconds % 900 == 0 ? totalSeconds / 900 : 127;

   748      *  out.writeByte(offsetByte);

   749      *  if (offsetByte == 127) {

   750      *    out.writeInt(totalSeconds);

   751      *  }

   752      * </pre>

   753      *

   754      * @return the instance of {@code Ser}, not null

   755      */

   756     private Object writeReplace() {

   757         return new Ser(Ser.ZONE_OFFSET_TYPE, this);

   758     }

   759 

   760     /**

   761      * Defend against malicious streams.

   762      * @return never

   763      * @throws InvalidObjectException always

   764      */

   765     private Object readResolve() throws ObjectStreamException {

   766         throw new InvalidObjectException("Deserialization via serialization delegate");

   767     }

   768 

   769     @Override

   770     void write(DataOutput out) throws IOException {

   771         out.writeByte(Ser.ZONE_OFFSET_TYPE);

   772         writeExternal(out);

   773     }

   774 

   775     void writeExternal(DataOutput out) throws IOException {

   776         final int offsetSecs = totalSeconds;

   777         int offsetByte = offsetSecs % 900 == 0 ? offsetSecs / 900 : 127;  // compress to -72 to +72

   778         out.writeByte(offsetByte);

   779         if (offsetByte == 127) {

   780             out.writeInt(offsetSecs);

   781         }

   782     }

   783 

   784     static ZoneOffset readExternal(DataInput in) throws IOException {

   785         int offsetByte = in.readByte();

   786         return (offsetByte == 127 ? ZoneOffset.ofTotalSeconds(in.readInt()) : ZoneOffset.ofTotalSeconds(offsetByte * 900));

   787     }

   788 

   789 }