Java tutorial
/* * Copyright (c) 2012, 2019, 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 java.io.DataOutput; import java.io.IOException; import java.io.InvalidObjectException; import java.io.ObjectInputStream; import java.io.Serializable; import java.time.format.DateTimeFormatterBuilder; import java.time.format.TextStyle; import java.time.temporal.TemporalAccessor; import java.time.temporal.TemporalField; import java.time.temporal.TemporalQueries; import java.time.temporal.TemporalQuery; import java.time.temporal.UnsupportedTemporalTypeException; import java.time.zone.ZoneRules; import java.time.zone.ZoneRulesException; import java.time.zone.ZoneRulesProvider; import java.util.HashSet; import java.util.Locale; import java.util.Map; import java.util.Objects; import java.util.Set; import java.util.TimeZone; import static java.util.Map.entry; /** * A time-zone ID, such as {@code Europe/Paris}. * <p> * A {@code ZoneId} is used to identify the rules used to convert between * an {@link Instant} and a {@link LocalDateTime}. * There are two distinct types of ID: * <ul> * <li>Fixed offsets - a fully resolved offset from UTC/Greenwich, that uses * the same offset for all local date-times * <li>Geographical regions - an area where a specific set of rules for finding * the offset from UTC/Greenwich apply * </ul> * Most fixed offsets are represented by {@link ZoneOffset}. * Calling {@link #normalized()} on any {@code ZoneId} will ensure that a * fixed offset ID will be represented as a {@code ZoneOffset}. * <p> * The actual rules, describing when and how the offset changes, are defined by {@link ZoneRules}. * This class is simply an ID used to obtain the underlying rules. * This approach is taken because rules are defined by governments and change * frequently, whereas the ID is stable. * <p> * The distinction has other effects. Serializing the {@code ZoneId} will only send * the ID, whereas serializing the rules sends the entire data set. * Similarly, a comparison of two IDs only examines the ID, whereas * a comparison of two rules examines the entire data set. * * <h2>Time-zone IDs</h2> * The ID is unique within the system. * There are three types of ID. * <p> * The simplest type of ID is that from {@code ZoneOffset}. * This consists of 'Z' and IDs starting with '+' or '-'. * <p> * The next type of ID are offset-style IDs with some form of prefix, * such as 'GMT+2' or 'UTC+01:00'. * The recognised prefixes are 'UTC', 'GMT' and 'UT'. * The offset is the suffix and will be normalized during creation. * These IDs can be normalized to a {@code ZoneOffset} using {@code normalized()}. * <p> * The third type of ID are region-based IDs. A region-based ID must be of * two or more characters, and not start with 'UTC', 'GMT', 'UT' '+' or '-'. * Region-based IDs are defined by configuration, see {@link ZoneRulesProvider}. * The configuration focuses on providing the lookup from the ID to the * underlying {@code ZoneRules}. * <p> * Time-zone rules are defined by governments and change frequently. * There are a number of organizations, known here as groups, that monitor * time-zone changes and collate them. * The default group is the IANA Time Zone Database (TZDB). * Other organizations include IATA (the airline industry body) and Microsoft. * <p> * Each group defines its own format for the region ID it provides. * The TZDB group defines IDs such as 'Europe/London' or 'America/New_York'. * TZDB IDs take precedence over other groups. * <p> * It is strongly recommended that the group name is included in all IDs supplied by * groups other than TZDB to avoid conflicts. For example, IATA airline time-zone * region IDs are typically the same as the three letter airport code. * However, the airport of Utrecht has the code 'UTC', which is obviously a conflict. * The recommended format for region IDs from groups other than TZDB is 'group~region'. * Thus if IATA data were defined, Utrecht airport would be 'IATA~UTC'. * * <h2>Serialization</h2> * This class can be serialized and stores the string zone ID in the external form. * The {@code ZoneOffset} subclass uses a dedicated format that only stores the * offset from UTC/Greenwich. * <p> * A {@code ZoneId} can be deserialized in a Java Runtime where the ID is unknown. * For example, if a server-side Java Runtime has been updated with a new zone ID, but * the client-side Java Runtime has not been updated. In this case, the {@code ZoneId} * object will exist, and can be queried using {@code getId}, {@code equals}, * {@code hashCode}, {@code toString}, {@code getDisplayName} and {@code normalized}. * However, any call to {@code getRules} will fail with {@code ZoneRulesException}. * This approach is designed to allow a {@link ZonedDateTime} to be loaded and * queried, but not modified, on a Java Runtime with incomplete time-zone information. * * <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 ZoneId} may have unpredictable results and should be avoided. * The {@code equals} method should be used for comparisons. * * @implSpec * This abstract class has two implementations, both of which are immutable and thread-safe. * One implementation models region-based IDs, the other is {@code ZoneOffset} modelling * offset-based IDs. This difference is visible in serialization. * * @since 1.8 */ public abstract class ZoneId implements Serializable { /** * A map of zone overrides to enable the short time-zone names to be used. * <p> * Use of short zone IDs has been deprecated in {@code java.util.TimeZone}. * This map allows the IDs to continue to be used via the * {@link #of(String, Map)} factory method. * <p> * This map contains a mapping of the IDs that is in line with TZDB 2005r and * later, where 'EST', 'MST' and 'HST' map to IDs which do not include daylight * savings. * <p> * This maps as follows: * <ul> * <li>EST - -05:00</li> * <li>HST - -10:00</li> * <li>MST - -07:00</li> * <li>ACT - Australia/Darwin</li> * <li>AET - Australia/Sydney</li> * <li>AGT - America/Argentina/Buenos_Aires</li> * <li>ART - Africa/Cairo</li> * <li>AST - America/Anchorage</li> * <li>BET - America/Sao_Paulo</li> * <li>BST - Asia/Dhaka</li> * <li>CAT - Africa/Harare</li> * <li>CNT - America/St_Johns</li> * <li>CST - America/Chicago</li> * <li>CTT - Asia/Shanghai</li> * <li>EAT - Africa/Addis_Ababa</li> * <li>ECT - Europe/Paris</li> * <li>IET - America/Indiana/Indianapolis</li> * <li>IST - Asia/Kolkata</li> * <li>JST - Asia/Tokyo</li> * <li>MIT - Pacific/Apia</li> * <li>NET - Asia/Yerevan</li> * <li>NST - Pacific/Auckland</li> * <li>PLT - Asia/Karachi</li> * <li>PNT - America/Phoenix</li> * <li>PRT - America/Puerto_Rico</li> * <li>PST - America/Los_Angeles</li> * <li>SST - Pacific/Guadalcanal</li> * <li>VST - Asia/Ho_Chi_Minh</li> * </ul> * The map is unmodifiable. */ public static final Map<String, String> SHORT_IDS = Map.ofEntries(entry("ACT", "Australia/Darwin"), entry("AET", "Australia/Sydney"), entry("AGT", "America/Argentina/Buenos_Aires"), entry("ART", "Africa/Cairo"), entry("AST", "America/Anchorage"), entry("BET", "America/Sao_Paulo"), entry("BST", "Asia/Dhaka"), entry("CAT", "Africa/Harare"), entry("CNT", "America/St_Johns"), entry("CST", "America/Chicago"), entry("CTT", "Asia/Shanghai"), entry("EAT", "Africa/Addis_Ababa"), entry("ECT", "Europe/Paris"), entry("IET", "America/Indiana/Indianapolis"), entry("IST", "Asia/Kolkata"), entry("JST", "Asia/Tokyo"), entry("MIT", "Pacific/Apia"), entry("NET", "Asia/Yerevan"), entry("NST", "Pacific/Auckland"), entry("PLT", "Asia/Karachi"), entry("PNT", "America/Phoenix"), entry("PRT", "America/Puerto_Rico"), entry("PST", "America/Los_Angeles"), entry("SST", "Pacific/Guadalcanal"), entry("VST", "Asia/Ho_Chi_Minh"), entry("EST", "-05:00"), entry("MST", "-07:00"), entry("HST", "-10:00")); /** * Serialization version. */ private static final long serialVersionUID = 8352817235686L; //----------------------------------------------------------------------- /** * Gets the system default time-zone. * <p> * This queries {@link TimeZone#getDefault()} to find the default time-zone * and converts it to a {@code ZoneId}. If the system default time-zone is changed, * then the result of this method will also change. * * @return the zone ID, not null * @throws DateTimeException if the converted zone ID has an invalid format * @throws ZoneRulesException if the converted zone region ID cannot be found */ public static ZoneId systemDefault() { return TimeZone.getDefault().toZoneId(); } /** * Gets the set of available zone IDs. * <p> * This set includes the string form of all available region-based IDs. * Offset-based zone IDs are not included in the returned set. * The ID can be passed to {@link #of(String)} to create a {@code ZoneId}. * <p> * The set of zone IDs can increase over time, although in a typical application * the set of IDs is fixed. Each call to this method is thread-safe. * * @return a modifiable copy of the set of zone IDs, not null */ public static Set<String> getAvailableZoneIds() { return new HashSet<String>(ZoneRulesProvider.getAvailableZoneIds()); } //----------------------------------------------------------------------- /** * Obtains an instance of {@code ZoneId} using its ID using a map * of aliases to supplement the standard zone IDs. * <p> * Many users of time-zones use short abbreviations, such as PST for * 'Pacific Standard Time' and PDT for 'Pacific Daylight Time'. * These abbreviations are not unique, and so cannot be used as IDs. * This method allows a map of string to time-zone to be setup and reused * within an application. * * @param zoneId the time-zone ID, not null * @param aliasMap a map of alias zone IDs (typically abbreviations) to real zone IDs, not null * @return the zone ID, not null * @throws DateTimeException if the zone ID has an invalid format * @throws ZoneRulesException if the zone ID is a region ID that cannot be found */ public static ZoneId of(String zoneId, Map<String, String> aliasMap) { Objects.requireNonNull(zoneId, "zoneId"); Objects.requireNonNull(aliasMap, "aliasMap"); String id = Objects.requireNonNullElse(aliasMap.get(zoneId), zoneId); return of(id); } /** * Obtains an instance of {@code ZoneId} from an ID ensuring that the * ID is valid and available for use. * <p> * This method parses the ID producing a {@code ZoneId} or {@code ZoneOffset}. * A {@code ZoneOffset} is returned if the ID is 'Z', or starts with '+' or '-'. * The result will always be a valid ID for which {@link ZoneRules} can be obtained. * <p> * Parsing matches the zone ID step by step as follows. * <ul> * <li>If the zone ID equals 'Z', the result is {@code ZoneOffset.UTC}. * <li>If the zone ID consists of a single letter, the zone ID is invalid * and {@code DateTimeException} is thrown. * <li>If the zone ID starts with '+' or '-', the ID is parsed as a * {@code ZoneOffset} using {@link ZoneOffset#of(String)}. * <li>If the zone ID equals 'GMT', 'UTC' or 'UT' then the result is a {@code ZoneId} * with the same ID and rules equivalent to {@code ZoneOffset.UTC}. * <li>If the zone ID starts with 'UTC+', 'UTC-', 'GMT+', 'GMT-', 'UT+' or 'UT-' * then the ID is a prefixed offset-based ID. The ID is split in two, with * a two or three letter prefix and a suffix starting with the sign. * The suffix is parsed as a {@link ZoneOffset#of(String) ZoneOffset}. * The result will be a {@code ZoneId} with the specified UTC/GMT/UT prefix * and the normalized offset ID as per {@link ZoneOffset#getId()}. * The rules of the returned {@code ZoneId} will be equivalent to the * parsed {@code ZoneOffset}. * <li>All other IDs are parsed as region-based zone IDs. Region IDs must * match the regular expression <code>[A-Za-z][A-Za-z0-9~/._+-]+</code> * otherwise a {@code DateTimeException} is thrown. If the zone ID is not * in the configured set of IDs, {@code ZoneRulesException} is thrown. * The detailed format of the region ID depends on the group supplying the data. * The default set of data is supplied by the IANA Time Zone Database (TZDB). * This has region IDs of the form '{area}/{city}', such as 'Europe/Paris' or 'America/New_York'. * This is compatible with most IDs from {@link java.util.TimeZone}. * </ul> * * @param zoneId the time-zone ID, not null * @return the zone ID, not null * @throws DateTimeException if the zone ID has an invalid format * @throws ZoneRulesException if the zone ID is a region ID that cannot be found */ public static ZoneId of(String zoneId) { return of(zoneId, true); } /** * Obtains an instance of {@code ZoneId} wrapping an offset. * <p> * If the prefix is "GMT", "UTC", or "UT" a {@code ZoneId} * with the prefix and the non-zero offset is returned. * If the prefix is empty {@code ""} the {@code ZoneOffset} is returned. * * @param prefix the time-zone ID, not null * @param offset the offset, not null * @return the zone ID, not null * @throws IllegalArgumentException if the prefix is not one of * "GMT", "UTC", or "UT", or "" */ public static ZoneId ofOffset(String prefix, ZoneOffset offset) { Objects.requireNonNull(prefix, "prefix"); Objects.requireNonNull(offset, "offset"); if (prefix.isEmpty()) { return offset; } if (!prefix.equals("GMT") && !prefix.equals("UTC") && !prefix.equals("UT")) { throw new IllegalArgumentException("prefix should be GMT, UTC or UT, is: " + prefix); } if (offset.getTotalSeconds() != 0) { prefix = prefix.concat(offset.getId()); } return new ZoneRegion(prefix, offset.getRules()); } /** * Parses the ID, taking a flag to indicate whether {@code ZoneRulesException} * should be thrown or not, used in deserialization. * * @param zoneId the time-zone ID, not null * @param checkAvailable whether to check if the zone ID is available * @return the zone ID, not null * @throws DateTimeException if the ID format is invalid * @throws ZoneRulesException if checking availability and the ID cannot be found */ static ZoneId of(String zoneId, boolean checkAvailable) { Objects.requireNonNull(zoneId, "zoneId"); if (zoneId.length() <= 1 || zoneId.startsWith("+") || zoneId.startsWith("-")) { return ZoneOffset.of(zoneId); } else if (zoneId.startsWith("UTC") || zoneId.startsWith("GMT")) { return ofWithPrefix(zoneId, 3, checkAvailable); } else if (zoneId.startsWith("UT")) { return ofWithPrefix(zoneId, 2, checkAvailable); } return ZoneRegion.ofId(zoneId, checkAvailable); } /** * Parse once a prefix is established. * * @param zoneId the time-zone ID, not null * @param prefixLength the length of the prefix, 2 or 3 * @return the zone ID, not null * @throws DateTimeException if the zone ID has an invalid format */ private static ZoneId ofWithPrefix(String zoneId, int prefixLength, boolean checkAvailable) { String prefix = zoneId.substring(0, prefixLength); if (zoneId.length() == prefixLength) { return ofOffset(prefix, ZoneOffset.UTC); } if (zoneId.charAt(prefixLength) != '+' && zoneId.charAt(prefixLength) != '-') { return ZoneRegion.ofId(zoneId, checkAvailable); // drop through to ZoneRulesProvider } try { ZoneOffset offset = ZoneOffset.of(zoneId.substring(prefixLength)); if (offset == ZoneOffset.UTC) { return ofOffset(prefix, offset); } return ofOffset(prefix, offset); } catch (DateTimeException ex) { throw new DateTimeException("Invalid ID for offset-based ZoneId: " + zoneId, ex); } } //----------------------------------------------------------------------- /** * Obtains an instance of {@code ZoneId} from a temporal object. * <p> * This obtains a zone 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 ZoneId}. * <p> * A {@code TemporalAccessor} represents some form of date and time information. * This factory converts the arbitrary temporal object to an instance of {@code ZoneId}. * <p> * The conversion will try to obtain the zone in a way that favours region-based * zones over offset-based zones using {@link TemporalQueries#zone()}. * <p> * This method matches the signature of the functional interface {@link TemporalQuery} * allowing it to be used as a query via method reference, {@code ZoneId::from}. * * @param temporal the temporal object to convert, not null * @return the zone ID, not null * @throws DateTimeException if unable to convert to a {@code ZoneId} */ public static ZoneId from(TemporalAccessor temporal) { ZoneId obj = temporal.query(TemporalQueries.zone()); if (obj == null) { throw new DateTimeException("Unable to obtain ZoneId from TemporalAccessor: " + temporal + " of type " + temporal.getClass().getName()); } return obj; } //----------------------------------------------------------------------- /** * Constructor only accessible within the package. */ ZoneId() { if (getClass() != ZoneOffset.class && getClass() != ZoneRegion.class) { throw new AssertionError("Invalid subclass"); } } //----------------------------------------------------------------------- /** * Gets the unique time-zone ID. * <p> * This ID uniquely defines this object. * The format of an offset based ID is defined by {@link ZoneOffset#getId()}. * * @return the time-zone unique ID, not null */ public abstract String getId(); //----------------------------------------------------------------------- /** * Gets the textual representation of the zone, such as 'British Time' or * '+02:00'. * <p> * This returns the textual name used to identify the time-zone ID, * suitable for presentation to the user. * The parameters control the style of the returned text and the locale. * <p> * If no textual mapping is found then the {@link #getId() full ID} is returned. * * @param style the length of the text required, not null * @param locale the locale to use, not null * @return the text value of the zone, not null */ public String getDisplayName(TextStyle style, Locale locale) { return new DateTimeFormatterBuilder().appendZoneText(style).toFormatter(locale).format(toTemporal()); } /** * Converts this zone to a {@code TemporalAccessor}. * <p> * A {@code ZoneId} can be fully represented as a {@code TemporalAccessor}. * However, the interface is not implemented by this class as most of the * methods on the interface have no meaning to {@code ZoneId}. * <p> * The returned temporal has no supported fields, with the query method * supporting the return of the zone using {@link TemporalQueries#zoneId()}. * * @return a temporal equivalent to this zone, not null */ private TemporalAccessor toTemporal() { return new TemporalAccessor() { @Override public boolean isSupported(TemporalField field) { return false; } @Override public long getLong(TemporalField field) { throw new UnsupportedTemporalTypeException("Unsupported field: " + field); } @SuppressWarnings("unchecked") @Override public <R> R query(TemporalQuery<R> query) { if (query == TemporalQueries.zoneId()) { return (R) ZoneId.this; } return TemporalAccessor.super.query(query); } }; } //----------------------------------------------------------------------- /** * Gets the time-zone rules for this ID allowing calculations to be performed. * <p> * The rules provide the functionality associated with a time-zone, * such as finding the offset for a given instant or local date-time. * <p> * A time-zone can be invalid if it is deserialized in a Java Runtime which * does not have the same rules loaded as the Java Runtime that stored it. * In this case, calling this method will throw a {@code ZoneRulesException}. * <p> * The rules are supplied by {@link ZoneRulesProvider}. An advanced provider may * support dynamic updates to the rules without restarting the Java Runtime. * If so, then the result of this method may change over time. * Each individual call will be still remain thread-safe. * <p> * {@link ZoneOffset} will always return a set of rules where the offset never changes. * * @return the rules, not null * @throws ZoneRulesException if no rules are available for this ID */ public abstract ZoneRules getRules(); /** * Normalizes the time-zone ID, returning a {@code ZoneOffset} where possible. * <p> * The returns a normalized {@code ZoneId} that can be used in place of this ID. * The result will have {@code ZoneRules} equivalent to those returned by this object, * however the ID returned by {@code getId()} may be different. * <p> * The normalization checks if the rules of this {@code ZoneId} have a fixed offset. * If they do, then the {@code ZoneOffset} equal to that offset is returned. * Otherwise {@code this} is returned. * * @return the time-zone unique ID, not null */ public ZoneId normalized() { try { ZoneRules rules = getRules(); if (rules.isFixedOffset()) { return rules.getOffset(Instant.EPOCH); } } catch (ZoneRulesException ex) { // invalid ZoneRegion is not important to this method } return this; } //----------------------------------------------------------------------- /** * Checks if this time-zone ID is equal to another time-zone ID. * <p> * The comparison is based on the ID. * * @param obj the object to check, null returns false * @return true if this is equal to the other time-zone ID */ @Override public boolean equals(Object obj) { if (this == obj) { return true; } if (obj instanceof ZoneId) { ZoneId other = (ZoneId) obj; return getId().equals(other.getId()); } return false; } /** * A hash code for this time-zone ID. * * @return a suitable hash code */ @Override public int hashCode() { return getId().hashCode(); } //----------------------------------------------------------------------- /** * 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"); } /** * Outputs this zone as a {@code String}, using the ID. * * @return a string representation of this time-zone ID, not null */ @Override public String toString() { return getId(); } //----------------------------------------------------------------------- /** * Writes the object using a * <a href="{@docRoot}/serialized-form.html#java.time.Ser">dedicated serialized form</a>. * @serialData * <pre> * out.writeByte(7); // identifies a ZoneId (not ZoneOffset) * out.writeUTF(getId()); * </pre> * <p> * When read back in, the {@code ZoneId} will be created as though using * {@link #of(String)}, but without any exception in the case where the * ID has a valid format, but is not in the known set of region-based IDs. * * @return the instance of {@code Ser}, not null */ // this is here for serialization Javadoc private Object writeReplace() { return new Ser(Ser.ZONE_REGION_TYPE, this); } abstract void write(DataOutput out) throws IOException; }