Java tutorial
/* * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ /* * This file is available under and governed by the GNU General Public * License version 2 only, as published by the Free Software Foundation. * However, the following notice accompanied the original version of this * file: * * Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos * * All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are met: * * * Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * * * Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * * * Neither the name of JSR-310 nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ package java.time; import static java.time.LocalTime.MINUTES_PER_HOUR; import static java.time.LocalTime.SECONDS_PER_HOUR; import static java.time.LocalTime.SECONDS_PER_MINUTE; import static java.time.temporal.ChronoField.OFFSET_SECONDS; import java.io.DataInput; import java.io.DataOutput; import java.io.IOException; import java.io.InvalidObjectException; import java.io.ObjectInputStream; import java.io.Serializable; import java.time.temporal.ChronoField; import java.time.temporal.Temporal; import java.time.temporal.TemporalAccessor; import java.time.temporal.TemporalAdjuster; import java.time.temporal.TemporalField; import java.time.temporal.TemporalQueries; import java.time.temporal.TemporalQuery; import java.time.temporal.UnsupportedTemporalTypeException; import java.time.temporal.ValueRange; import java.time.zone.ZoneRules; import java.util.Objects; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; /** * A time-zone offset from Greenwich/UTC, such as {@code +02:00}. * <p> * A time-zone offset is the amount of time that a time-zone differs from Greenwich/UTC. * This is usually a fixed number of hours and minutes. * <p> * Different parts of the world have different time-zone offsets. * The rules for how offsets vary by place and time of year are captured in the * {@link ZoneId} class. * <p> * For example, Paris is one hour ahead of Greenwich/UTC in winter and two hours * ahead in summer. The {@code ZoneId} instance for Paris will reference two * {@code ZoneOffset} instances - a {@code +01:00} instance for winter, * and a {@code +02:00} instance for summer. * <p> * In 2008, time-zone offsets around the world extended from -12:00 to +14:00. * To prevent any problems with that range being extended, yet still provide * validation, the range of offsets is restricted to -18:00 to 18:00 inclusive. * <p> * This class is designed for use with the ISO calendar system. * The fields of hours, minutes and seconds make assumptions that are valid for the * standard ISO definitions of those fields. This class may be used with other * calendar systems providing the definition of the time fields matches those * of the ISO calendar system. * <p> * Instances of {@code ZoneOffset} must be compared using {@link #equals}. * Implementations may choose to cache certain common offsets, however * applications must not rely on such caching. * * <p> * This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a> * class; use of identity-sensitive operations (including reference equality * ({@code ==}), identity hash code, or synchronization) on instances of * {@code ZoneOffset} may have unpredictable results and should be avoided. * The {@code equals} method should be used for comparisons. * * @implSpec * This class is immutable and thread-safe. * * @since 1.8 */ public final class ZoneOffset extends ZoneId implements TemporalAccessor, TemporalAdjuster, Comparable<ZoneOffset>, Serializable { /** Cache of time-zone offset by offset in seconds. */ private static final ConcurrentMap<Integer, ZoneOffset> SECONDS_CACHE = new ConcurrentHashMap<>(16, 0.75f, 4); /** Cache of time-zone offset by ID. */ private static final ConcurrentMap<String, ZoneOffset> ID_CACHE = new ConcurrentHashMap<>(16, 0.75f, 4); /** * The abs maximum seconds. */ private static final int MAX_SECONDS = 18 * SECONDS_PER_HOUR; /** * Serialization version. */ private static final long serialVersionUID = 2357656521762053153L; /** * The time-zone offset for UTC, with an ID of 'Z'. */ public static final ZoneOffset UTC = ZoneOffset.ofTotalSeconds(0); /** * Constant for the minimum supported offset. */ public static final ZoneOffset MIN = ZoneOffset.ofTotalSeconds(-MAX_SECONDS); /** * Constant for the maximum supported offset. */ public static final ZoneOffset MAX = ZoneOffset.ofTotalSeconds(MAX_SECONDS); /** * The total offset in seconds. */ private final int totalSeconds; /** * The string form of the time-zone offset. */ private final transient String id; //----------------------------------------------------------------------- /** * Obtains an instance of {@code ZoneOffset} using the ID. * <p> * This method parses the string ID of a {@code ZoneOffset} to * return an instance. The parsing accepts all the formats generated by * {@link #getId()}, plus some additional formats: * <ul> * <li>{@code Z} - for UTC * <li>{@code +h} * <li>{@code +hh} * <li>{@code +hh:mm} * <li>{@code -hh:mm} * <li>{@code +hhmm} * <li>{@code -hhmm} * <li>{@code +hh:mm:ss} * <li>{@code -hh:mm:ss} * <li>{@code +hhmmss} * <li>{@code -hhmmss} * </ul> * Note that ± means either the plus or minus symbol. * <p> * The ID of the returned offset will be normalized to one of the formats * described by {@link #getId()}. * <p> * The maximum supported range is from +18:00 to -18:00 inclusive. * * @param offsetId the offset ID, not null * @return the zone-offset, not null * @throws DateTimeException if the offset ID is invalid */ @SuppressWarnings("fallthrough") public static ZoneOffset of(String offsetId) { Objects.requireNonNull(offsetId, "offsetId"); // "Z" is always in the cache ZoneOffset offset = ID_CACHE.get(offsetId); if (offset != null) { return offset; } // parse - +h, +hh, +hhmm, +hh:mm, +hhmmss, +hh:mm:ss final int hours, minutes, seconds; switch (offsetId.length()) { case 2: offsetId = offsetId.charAt(0) + "0" + offsetId.charAt(1); // fallthru case 3: hours = parseNumber(offsetId, 1, false); minutes = 0; seconds = 0; break; case 5: hours = parseNumber(offsetId, 1, false); minutes = parseNumber(offsetId, 3, false); seconds = 0; break; case 6: hours = parseNumber(offsetId, 1, false); minutes = parseNumber(offsetId, 4, true); seconds = 0; break; case 7: hours = parseNumber(offsetId, 1, false); minutes = parseNumber(offsetId, 3, false); seconds = parseNumber(offsetId, 5, false); break; case 9: hours = parseNumber(offsetId, 1, false); minutes = parseNumber(offsetId, 4, true); seconds = parseNumber(offsetId, 7, true); break; default: throw new DateTimeException("Invalid ID for ZoneOffset, invalid format: " + offsetId); } char first = offsetId.charAt(0); if (first != '+' && first != '-') { throw new DateTimeException( "Invalid ID for ZoneOffset, plus/minus not found when expected: " + offsetId); } if (first == '-') { return ofHoursMinutesSeconds(-hours, -minutes, -seconds); } else { return ofHoursMinutesSeconds(hours, minutes, seconds); } } /** * Parse a two digit zero-prefixed number. * * @param offsetId the offset ID, not null * @param pos the position to parse, valid * @param precededByColon should this number be prefixed by a precededByColon * @return the parsed number, from 0 to 99 */ private static int parseNumber(CharSequence offsetId, int pos, boolean precededByColon) { if (precededByColon && offsetId.charAt(pos - 1) != ':') { throw new DateTimeException("Invalid ID for ZoneOffset, colon not found when expected: " + offsetId); } char ch1 = offsetId.charAt(pos); char ch2 = offsetId.charAt(pos + 1); if (ch1 < '0' || ch1 > '9' || ch2 < '0' || ch2 > '9') { throw new DateTimeException("Invalid ID for ZoneOffset, non numeric characters found: " + offsetId); } return (ch1 - 48) * 10 + (ch2 - 48); } //----------------------------------------------------------------------- /** * Obtains an instance of {@code ZoneOffset} using an offset in hours. * * @param hours the time-zone offset in hours, from -18 to +18 * @return the zone-offset, not null * @throws DateTimeException if the offset is not in the required range */ public static ZoneOffset ofHours(int hours) { return ofHoursMinutesSeconds(hours, 0, 0); } /** * Obtains an instance of {@code ZoneOffset} using an offset in * hours and minutes. * <p> * The sign of the hours and minutes components must match. * Thus, if the hours is negative, the minutes must be negative or zero. * If the hours is zero, the minutes may be positive, negative or zero. * * @param hours the time-zone offset in hours, from -18 to +18 * @param minutes the time-zone offset in minutes, from 0 to ±59, sign matches hours * @return the zone-offset, not null * @throws DateTimeException if the offset is not in the required range */ public static ZoneOffset ofHoursMinutes(int hours, int minutes) { return ofHoursMinutesSeconds(hours, minutes, 0); } /** * Obtains an instance of {@code ZoneOffset} using an offset in * hours, minutes and seconds. * <p> * The sign of the hours, minutes and seconds components must match. * Thus, if the hours is negative, the minutes and seconds must be negative or zero. * * @param hours the time-zone offset in hours, from -18 to +18 * @param minutes the time-zone offset in minutes, from 0 to ±59, sign matches hours and seconds * @param seconds the time-zone offset in seconds, from 0 to ±59, sign matches hours and minutes * @return the zone-offset, not null * @throws DateTimeException if the offset is not in the required range */ public static ZoneOffset ofHoursMinutesSeconds(int hours, int minutes, int seconds) { validate(hours, minutes, seconds); int totalSeconds = totalSeconds(hours, minutes, seconds); return ofTotalSeconds(totalSeconds); } //----------------------------------------------------------------------- /** * Obtains an instance of {@code ZoneOffset} from a temporal object. * <p> * This obtains an offset based on the specified temporal. * A {@code TemporalAccessor} represents an arbitrary set of date and time information, * which this factory converts to an instance of {@code ZoneOffset}. * <p> * A {@code TemporalAccessor} represents some form of date and time information. * This factory converts the arbitrary temporal object to an instance of {@code ZoneOffset}. * <p> * The conversion uses the {@link TemporalQueries#offset()} query, which relies * on extracting the {@link ChronoField#OFFSET_SECONDS OFFSET_SECONDS} field. * <p> * This method matches the signature of the functional interface {@link TemporalQuery} * allowing it to be used as a query via method reference, {@code ZoneOffset::from}. * * @param temporal the temporal object to convert, not null * @return the zone-offset, not null * @throws DateTimeException if unable to convert to an {@code ZoneOffset} */ public static ZoneOffset from(TemporalAccessor temporal) { Objects.requireNonNull(temporal, "temporal"); ZoneOffset offset = temporal.query(TemporalQueries.offset()); if (offset == null) { throw new DateTimeException("Unable to obtain ZoneOffset from TemporalAccessor: " + temporal + " of type " + temporal.getClass().getName()); } return offset; } //----------------------------------------------------------------------- /** * Validates the offset fields. * * @param hours the time-zone offset in hours, from -18 to +18 * @param minutes the time-zone offset in minutes, from 0 to ±59 * @param seconds the time-zone offset in seconds, from 0 to ±59 * @throws DateTimeException if the offset is not in the required range */ private static void validate(int hours, int minutes, int seconds) { if (hours < -18 || hours > 18) { throw new DateTimeException( "Zone offset hours not in valid range: value " + hours + " is not in the range -18 to 18"); } if (hours > 0) { if (minutes < 0 || seconds < 0) { throw new DateTimeException( "Zone offset minutes and seconds must be positive because hours is positive"); } } else if (hours < 0) { if (minutes > 0 || seconds > 0) { throw new DateTimeException( "Zone offset minutes and seconds must be negative because hours is negative"); } } else if ((minutes > 0 && seconds < 0) || (minutes < 0 && seconds > 0)) { throw new DateTimeException("Zone offset minutes and seconds must have the same sign"); } if (minutes < -59 || minutes > 59) { throw new DateTimeException( "Zone offset minutes not in valid range: value " + minutes + " is not in the range -59 to 59"); } if (seconds < -59 || seconds > 59) { throw new DateTimeException( "Zone offset seconds not in valid range: value " + seconds + " is not in the range -59 to 59"); } if (Math.abs(hours) == 18 && (minutes | seconds) != 0) { throw new DateTimeException("Zone offset not in valid range: -18:00 to +18:00"); } } /** * Calculates the total offset in seconds. * * @param hours the time-zone offset in hours, from -18 to +18 * @param minutes the time-zone offset in minutes, from 0 to ±59, sign matches hours and seconds * @param seconds the time-zone offset in seconds, from 0 to ±59, sign matches hours and minutes * @return the total in seconds */ private static int totalSeconds(int hours, int minutes, int seconds) { return hours * SECONDS_PER_HOUR + minutes * SECONDS_PER_MINUTE + seconds; } //----------------------------------------------------------------------- /** * Obtains an instance of {@code ZoneOffset} specifying the total offset in seconds * <p> * The offset must be in the range {@code -18:00} to {@code +18:00}, which corresponds to -64800 to +64800. * * @param totalSeconds the total time-zone offset in seconds, from -64800 to +64800 * @return the ZoneOffset, not null * @throws DateTimeException if the offset is not in the required range */ public static ZoneOffset ofTotalSeconds(int totalSeconds) { if (totalSeconds < -MAX_SECONDS || totalSeconds > MAX_SECONDS) { throw new DateTimeException("Zone offset not in valid range: -18:00 to +18:00"); } if (totalSeconds % (15 * SECONDS_PER_MINUTE) == 0) { Integer totalSecs = totalSeconds; ZoneOffset result = SECONDS_CACHE.get(totalSecs); if (result == null) { result = new ZoneOffset(totalSeconds); SECONDS_CACHE.putIfAbsent(totalSecs, result); result = SECONDS_CACHE.get(totalSecs); ID_CACHE.putIfAbsent(result.getId(), result); } return result; } else { return new ZoneOffset(totalSeconds); } } //----------------------------------------------------------------------- /** * Constructor. * * @param totalSeconds the total time-zone offset in seconds, from -64800 to +64800 */ private ZoneOffset(int totalSeconds) { super(); this.totalSeconds = totalSeconds; id = buildId(totalSeconds); } private static String buildId(int totalSeconds) { if (totalSeconds == 0) { return "Z"; } else { int absTotalSeconds = Math.abs(totalSeconds); StringBuilder buf = new StringBuilder(); int absHours = absTotalSeconds / SECONDS_PER_HOUR; int absMinutes = (absTotalSeconds / SECONDS_PER_MINUTE) % MINUTES_PER_HOUR; buf.append(totalSeconds < 0 ? "-" : "+").append(absHours < 10 ? "0" : "").append(absHours) .append(absMinutes < 10 ? ":0" : ":").append(absMinutes); int absSeconds = absTotalSeconds % SECONDS_PER_MINUTE; if (absSeconds != 0) { buf.append(absSeconds < 10 ? ":0" : ":").append(absSeconds); } return buf.toString(); } } //----------------------------------------------------------------------- /** * Gets the total zone offset in seconds. * <p> * This is the primary way to access the offset amount. * It returns the total of the hours, minutes and seconds fields as a * single offset that can be added to a time. * * @return the total zone offset amount in seconds */ public int getTotalSeconds() { return totalSeconds; } /** * Gets the normalized zone offset ID. * <p> * The ID is minor variation to the standard ISO-8601 formatted string * for the offset. There are three formats: * <ul> * <li>{@code Z} - for UTC (ISO-8601) * <li>{@code +hh:mm} or {@code -hh:mm} - if the seconds are zero (ISO-8601) * <li>{@code +hh:mm:ss} or {@code -hh:mm:ss} - if the seconds are non-zero (not ISO-8601) * </ul> * * @return the zone offset ID, not null */ @Override public String getId() { return id; } /** * Gets the associated time-zone rules. * <p> * The rules will always return this offset when queried. * The implementation class is immutable, thread-safe and serializable. * * @return the rules, not null */ @Override public ZoneRules getRules() { return ZoneRules.of(this); } //----------------------------------------------------------------------- /** * Checks if the specified field is supported. * <p> * This checks if this offset can be queried for the specified field. * If false, then calling the {@link #range(TemporalField) range} and * {@link #get(TemporalField) get} methods will throw an exception. * <p> * If the field is a {@link ChronoField} then the query is implemented here. * The {@code OFFSET_SECONDS} field returns true. * All other {@code ChronoField} instances will return false. * <p> * If the field is not a {@code ChronoField}, then the result of this method * is obtained by invoking {@code TemporalField.isSupportedBy(TemporalAccessor)} * passing {@code this} as the argument. * Whether the field is supported is determined by the field. * * @param field the field to check, null returns false * @return true if the field is supported on this offset, false if not */ @Override public boolean isSupported(TemporalField field) { if (field instanceof ChronoField) { return field == OFFSET_SECONDS; } return field != null && field.isSupportedBy(this); } /** * Gets the range of valid values for the specified field. * <p> * The range object expresses the minimum and maximum valid values for a field. * This offset is used to enhance the accuracy of the returned range. * If it is not possible to return the range, because the field is not supported * or for some other reason, an exception is thrown. * <p> * If the field is a {@link ChronoField} then the query is implemented here. * The {@link #isSupported(TemporalField) supported fields} will return * appropriate range instances. * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. * <p> * If the field is not a {@code ChronoField}, then the result of this method * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)} * passing {@code this} as the argument. * Whether the range can be obtained is determined by the field. * * @param field the field to query the range for, not null * @return the range of valid values for the field, not null * @throws DateTimeException if the range for the field cannot be obtained * @throws UnsupportedTemporalTypeException if the field is not supported */ @Override // override for Javadoc public ValueRange range(TemporalField field) { return TemporalAccessor.super.range(field); } /** * Gets the value of the specified field from this offset as an {@code int}. * <p> * This queries this offset for the value of the specified field. * The returned value will always be within the valid range of values for the field. * If it is not possible to return the value, because the field is not supported * or for some other reason, an exception is thrown. * <p> * If the field is a {@link ChronoField} then the query is implemented here. * The {@code OFFSET_SECONDS} field returns the value of the offset. * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. * <p> * If the field is not a {@code ChronoField}, then the result of this method * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)} * passing {@code this} as the argument. Whether the value can be obtained, * and what the value represents, is determined by the field. * * @param field the field to get, not null * @return the value for the field * @throws DateTimeException if a value for the field cannot be obtained or * the value is outside the range of valid values for the field * @throws UnsupportedTemporalTypeException if the field is not supported or * the range of values exceeds an {@code int} * @throws ArithmeticException if numeric overflow occurs */ @Override // override for Javadoc and performance public int get(TemporalField field) { if (field == OFFSET_SECONDS) { return totalSeconds; } else if (field instanceof ChronoField) { throw new UnsupportedTemporalTypeException("Unsupported field: " + field); } return range(field).checkValidIntValue(getLong(field), field); } /** * Gets the value of the specified field from this offset as a {@code long}. * <p> * This queries this offset for the value of the specified field. * If it is not possible to return the value, because the field is not supported * or for some other reason, an exception is thrown. * <p> * If the field is a {@link ChronoField} then the query is implemented here. * The {@code OFFSET_SECONDS} field returns the value of the offset. * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}. * <p> * If the field is not a {@code ChronoField}, then the result of this method * is obtained by invoking {@code TemporalField.getFrom(TemporalAccessor)} * passing {@code this} as the argument. Whether the value can be obtained, * and what the value represents, is determined by the field. * * @param field the field to get, not null * @return the value for the field * @throws DateTimeException if a value for the field cannot be obtained * @throws UnsupportedTemporalTypeException if the field is not supported * @throws ArithmeticException if numeric overflow occurs */ @Override public long getLong(TemporalField field) { if (field == OFFSET_SECONDS) { return totalSeconds; } else if (field instanceof ChronoField) { throw new UnsupportedTemporalTypeException("Unsupported field: " + field); } return field.getFrom(this); } //----------------------------------------------------------------------- /** * Queries this offset using the specified query. * <p> * This queries this offset using the specified query strategy object. * The {@code TemporalQuery} object defines the logic to be used to * obtain the result. Read the documentation of the query to understand * what the result of this method will be. * <p> * The result of this method is obtained by invoking the * {@link TemporalQuery#queryFrom(TemporalAccessor)} method on the * specified query passing {@code this} as the argument. * * @param <R> the type of the result * @param query the query to invoke, not null * @return the query result, null may be returned (defined by the query) * @throws DateTimeException if unable to query (defined by the query) * @throws ArithmeticException if numeric overflow occurs (defined by the query) */ @SuppressWarnings("unchecked") @Override public <R> R query(TemporalQuery<R> query) { if (query == TemporalQueries.offset() || query == TemporalQueries.zone()) { return (R) this; } return TemporalAccessor.super.query(query); } /** * Adjusts the specified temporal object to have the same offset as this object. * <p> * This returns a temporal object of the same observable type as the input * with the offset changed to be the same as this. * <p> * The adjustment is equivalent to using {@link Temporal#with(TemporalField, long)} * passing {@link ChronoField#OFFSET_SECONDS} as the field. * <p> * In most cases, it is clearer to reverse the calling pattern by using * {@link Temporal#with(TemporalAdjuster)}: * <pre> * // these two lines are equivalent, but the second approach is recommended * temporal = thisOffset.adjustInto(temporal); * temporal = temporal.with(thisOffset); * </pre> * <p> * This instance is immutable and unaffected by this method call. * * @param temporal the target object to be adjusted, not null * @return the adjusted object, not null * @throws DateTimeException if unable to make the adjustment * @throws ArithmeticException if numeric overflow occurs */ @Override public Temporal adjustInto(Temporal temporal) { return temporal.with(OFFSET_SECONDS, totalSeconds); } //----------------------------------------------------------------------- /** * Compares this offset to another offset in descending order. * <p> * The offsets are compared in the order that they occur for the same time * of day around the world. Thus, an offset of {@code +10:00} comes before an * offset of {@code +09:00} and so on down to {@code -18:00}. * <p> * The comparison is "consistent with equals", as defined by {@link Comparable}. * * @param other the other date to compare to, not null * @return the comparator value, negative if less, positive if greater * @throws NullPointerException if {@code other} is null */ @Override public int compareTo(ZoneOffset other) { // abs(totalSeconds) <= MAX_SECONDS, so no overflow can happen here return other.totalSeconds - totalSeconds; } //----------------------------------------------------------------------- /** * Checks if this offset is equal to another offset. * <p> * The comparison is based on the amount of the offset in seconds. * This is equivalent to a comparison by ID. * * @param obj the object to check, null returns false * @return true if this is equal to the other offset */ @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj instanceof ZoneOffset) { return totalSeconds == ((ZoneOffset) obj).totalSeconds; } return false; } /** * A hash code for this offset. * * @return a suitable hash code */ @Override public int hashCode() { return totalSeconds; } //----------------------------------------------------------------------- /** * Outputs this offset as a {@code String}, using the normalized ID. * * @return a string representation of this offset, not null */ @Override public String toString() { return id; } // ----------------------------------------------------------------------- /** * Writes the object using a * <a href="{@docRoot}/serialized-form.html#java.time.Ser">dedicated serialized form</a>. * @serialData * <pre> * out.writeByte(8); // identifies a ZoneOffset * int offsetByte = totalSeconds % 900 == 0 ? totalSeconds / 900 : 127; * out.writeByte(offsetByte); * if (offsetByte == 127) { * out.writeInt(totalSeconds); * } * </pre> * * @return the instance of {@code Ser}, not null */ private Object writeReplace() { return new Ser(Ser.ZONE_OFFSET_TYPE, this); } /** * Defend against malicious streams. * * @param s the stream to read * @throws InvalidObjectException always */ private void readObject(ObjectInputStream s) throws InvalidObjectException { throw new InvalidObjectException("Deserialization via serialization delegate"); } @Override void write(DataOutput out) throws IOException { out.writeByte(Ser.ZONE_OFFSET_TYPE); writeExternal(out); } void writeExternal(DataOutput out) throws IOException { final int offsetSecs = totalSeconds; int offsetByte = offsetSecs % 900 == 0 ? offsetSecs / 900 : 127; // compress to -72 to +72 out.writeByte(offsetByte); if (offsetByte == 127) { out.writeInt(offsetSecs); } } static ZoneOffset readExternal(DataInput in) throws IOException { int offsetByte = in.readByte(); return (offsetByte == 127 ? ZoneOffset.ofTotalSeconds(in.readInt()) : ZoneOffset.ofTotalSeconds(offsetByte * 900)); } }