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/* * Copyright (c) 2012, 2013, 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.temporal; import static java.time.temporal.ChronoField.EPOCH_DAY; import static java.time.temporal.ChronoField.NANO_OF_DAY; import static java.time.temporal.ChronoField.OFFSET_SECONDS; import java.time.LocalDate; import java.time.LocalTime; import java.time.ZoneId; import java.time.ZoneOffset; import java.time.chrono.Chronology; /** * Common implementations of {@code TemporalQuery}. * <p> * This class provides common implementations of {@link TemporalQuery}. * These are defined here as they must be constants, and the definition * of lambdas does not guarantee that. By assigning them once here, * they become 'normal' Java constants. * <p> * Queries are a key tool for extracting information from temporal objects. * They exist to externalize the process of querying, permitting different * approaches, as per the strategy design pattern. * Examples might be a query that checks if the date is the day before February 29th * in a leap year, or calculates the number of days to your next birthday. * <p> * The {@link TemporalField} interface provides another mechanism for querying * temporal objects. That interface is limited to returning a {@code long}. * By contrast, queries can return any type. * <p> * There are two equivalent ways of using a {@code TemporalQuery}. * The first is to invoke the method on this interface directly. * The second is to use {@link TemporalAccessor#query(TemporalQuery)}: * <pre> * // these two lines are equivalent, but the second approach is recommended * temporal = thisQuery.queryFrom(temporal); * temporal = temporal.query(thisQuery); * </pre> * It is recommended to use the second approach, {@code query(TemporalQuery)}, * as it is a lot clearer to read in code. * <p> * The most common implementations are method references, such as * {@code LocalDate::from} and {@code ZoneId::from}. * Additional common queries are provided to return: * <ul> * <li> a Chronology, * <li> a LocalDate, * <li> a LocalTime, * <li> a ZoneOffset, * <li> a precision, * <li> a zone, or * <li> a zoneId. * </ul> * * @since 1.8 */ public final class TemporalQueries { // note that it is vital that each method supplies a constant, not a // calculated value, as they will be checked for using == // it is also vital that each constant is different (due to the == checking) // as such, alterations to this code must be done with care /** * Private constructor since this is a utility class. */ private TemporalQueries() { } //----------------------------------------------------------------------- // special constants should be used to extract information from a TemporalAccessor // that cannot be derived in other ways // Javadoc added here, so as to pretend they are more normal than they really are /** * A strict query for the {@code ZoneId}. * <p> * This queries a {@code TemporalAccessor} for the zone. * The zone is only returned if the date-time conceptually contains a {@code ZoneId}. * It will not be returned if the date-time only conceptually has an {@code ZoneOffset}. * Thus a {@link java.time.ZonedDateTime} will return the result of {@code getZone()}, * but an {@link java.time.OffsetDateTime} will return null. * <p> * In most cases, applications should use {@link #zone()} as this query is too strict. * <p> * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br> * {@code LocalDate} returns null<br> * {@code LocalTime} returns null<br> * {@code LocalDateTime} returns null<br> * {@code ZonedDateTime} returns the associated zone<br> * {@code OffsetTime} returns null<br> * {@code OffsetDateTime} returns null<br> * {@code ChronoLocalDate} returns null<br> * {@code ChronoLocalDateTime} returns null<br> * {@code ChronoZonedDateTime} returns the associated zone<br> * {@code Era} returns null<br> * {@code DayOfWeek} returns null<br> * {@code Month} returns null<br> * {@code Year} returns null<br> * {@code YearMonth} returns null<br> * {@code MonthDay} returns null<br> * {@code ZoneOffset} returns null<br> * {@code Instant} returns null<br> * * @return a query that can obtain the zone ID of a temporal, not null */ public static TemporalQuery<ZoneId> zoneId() { return TemporalQueries.ZONE_ID; } /** * A query for the {@code Chronology}. * <p> * This queries a {@code TemporalAccessor} for the chronology. * If the target {@code TemporalAccessor} represents a date, or part of a date, * then it should return the chronology that the date is expressed in. * As a result of this definition, objects only representing time, such as * {@code LocalTime}, will return null. * <p> * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br> * {@code LocalDate} returns {@code IsoChronology.INSTANCE}<br> * {@code LocalTime} returns null (does not represent a date)<br> * {@code LocalDateTime} returns {@code IsoChronology.INSTANCE}<br> * {@code ZonedDateTime} returns {@code IsoChronology.INSTANCE}<br> * {@code OffsetTime} returns null (does not represent a date)<br> * {@code OffsetDateTime} returns {@code IsoChronology.INSTANCE}<br> * {@code ChronoLocalDate} returns the associated chronology<br> * {@code ChronoLocalDateTime} returns the associated chronology<br> * {@code ChronoZonedDateTime} returns the associated chronology<br> * {@code Era} returns the associated chronology<br> * {@code DayOfWeek} returns null (shared across chronologies)<br> * {@code Month} returns {@code IsoChronology.INSTANCE}<br> * {@code Year} returns {@code IsoChronology.INSTANCE}<br> * {@code YearMonth} returns {@code IsoChronology.INSTANCE}<br> * {@code MonthDay} returns null {@code IsoChronology.INSTANCE}<br> * {@code ZoneOffset} returns null (does not represent a date)<br> * {@code Instant} returns null (does not represent a date)<br> * <p> * The method {@link java.time.chrono.Chronology#from(TemporalAccessor)} can be used as a * {@code TemporalQuery} via a method reference, {@code Chronology::from}. * That method is equivalent to this query, except that it throws an * exception if a chronology cannot be obtained. * * @return a query that can obtain the chronology of a temporal, not null */ public static TemporalQuery<Chronology> chronology() { return TemporalQueries.CHRONO; } /** * A query for the smallest supported unit. * <p> * This queries a {@code TemporalAccessor} for the time precision. * If the target {@code TemporalAccessor} represents a consistent or complete date-time, * date or time then this must return the smallest precision actually supported. * Note that fields such as {@code NANO_OF_DAY} and {@code NANO_OF_SECOND} * are defined to always return ignoring the precision, thus this is the only * way to find the actual smallest supported unit. * For example, were {@code GregorianCalendar} to implement {@code TemporalAccessor} * it would return a precision of {@code MILLIS}. * <p> * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br> * {@code LocalDate} returns {@code DAYS}<br> * {@code LocalTime} returns {@code NANOS}<br> * {@code LocalDateTime} returns {@code NANOS}<br> * {@code ZonedDateTime} returns {@code NANOS}<br> * {@code OffsetTime} returns {@code NANOS}<br> * {@code OffsetDateTime} returns {@code NANOS}<br> * {@code ChronoLocalDate} returns {@code DAYS}<br> * {@code ChronoLocalDateTime} returns {@code NANOS}<br> * {@code ChronoZonedDateTime} returns {@code NANOS}<br> * {@code Era} returns {@code ERAS}<br> * {@code DayOfWeek} returns {@code DAYS}<br> * {@code Month} returns {@code MONTHS}<br> * {@code Year} returns {@code YEARS}<br> * {@code YearMonth} returns {@code MONTHS}<br> * {@code MonthDay} returns null (does not represent a complete date or time)<br> * {@code ZoneOffset} returns null (does not represent a date or time)<br> * {@code Instant} returns {@code NANOS}<br> * * @return a query that can obtain the precision of a temporal, not null */ public static TemporalQuery<TemporalUnit> precision() { return TemporalQueries.PRECISION; } //----------------------------------------------------------------------- // non-special constants are standard queries that derive information from other information /** * A lenient query for the {@code ZoneId}, falling back to the {@code ZoneOffset}. * <p> * This queries a {@code TemporalAccessor} for the zone. * It first tries to obtain the zone, using {@link #zoneId()}. * If that is not found it tries to obtain the {@link #offset()}. * Thus a {@link java.time.ZonedDateTime} will return the result of {@code getZone()}, * while an {@link java.time.OffsetDateTime} will return the result of {@code getOffset()}. * <p> * In most cases, applications should use this query rather than {@code #zoneId()}. * <p> * The method {@link ZoneId#from(TemporalAccessor)} can be used as a * {@code TemporalQuery} via a method reference, {@code ZoneId::from}. * That method is equivalent to this query, except that it throws an * exception if a zone cannot be obtained. * * @return a query that can obtain the zone ID or offset of a temporal, not null */ public static TemporalQuery<ZoneId> zone() { return TemporalQueries.ZONE; } /** * A query for {@code ZoneOffset} returning null if not found. * <p> * This returns a {@code TemporalQuery} that can be used to query a temporal * object for the offset. The query will return null if the temporal * object cannot supply an offset. * <p> * The query implementation examines the {@link ChronoField#OFFSET_SECONDS OFFSET_SECONDS} * field and uses it to create a {@code ZoneOffset}. * <p> * The method {@link java.time.ZoneOffset#from(TemporalAccessor)} can be used as a * {@code TemporalQuery} via a method reference, {@code ZoneOffset::from}. * This query and {@code ZoneOffset::from} will return the same result if the * temporal object contains an offset. If the temporal object does not contain * an offset, then the method reference will throw an exception, whereas this * query will return null. * * @return a query that can obtain the offset of a temporal, not null */ public static TemporalQuery<ZoneOffset> offset() { return TemporalQueries.OFFSET; } /** * A query for {@code LocalDate} returning null if not found. * <p> * This returns a {@code TemporalQuery} that can be used to query a temporal * object for the local date. The query will return null if the temporal * object cannot supply a local date. * <p> * The query implementation examines the {@link ChronoField#EPOCH_DAY EPOCH_DAY} * field and uses it to create a {@code LocalDate}. * <p> * The method {@link ZoneOffset#from(TemporalAccessor)} can be used as a * {@code TemporalQuery} via a method reference, {@code LocalDate::from}. * This query and {@code LocalDate::from} will return the same result if the * temporal object contains a date. If the temporal object does not contain * a date, then the method reference will throw an exception, whereas this * query will return null. * * @return a query that can obtain the date of a temporal, not null */ public static TemporalQuery<LocalDate> localDate() { return TemporalQueries.LOCAL_DATE; } /** * A query for {@code LocalTime} returning null if not found. * <p> * This returns a {@code TemporalQuery} that can be used to query a temporal * object for the local time. The query will return null if the temporal * object cannot supply a local time. * <p> * The query implementation examines the {@link ChronoField#NANO_OF_DAY NANO_OF_DAY} * field and uses it to create a {@code LocalTime}. * <p> * The method {@link ZoneOffset#from(TemporalAccessor)} can be used as a * {@code TemporalQuery} via a method reference, {@code LocalTime::from}. * This query and {@code LocalTime::from} will return the same result if the * temporal object contains a time. If the temporal object does not contain * a time, then the method reference will throw an exception, whereas this * query will return null. * * @return a query that can obtain the time of a temporal, not null */ public static TemporalQuery<LocalTime> localTime() { return TemporalQueries.LOCAL_TIME; } //----------------------------------------------------------------------- /** * A strict query for the {@code ZoneId}. */ static final TemporalQuery<ZoneId> ZONE_ID = new TemporalQuery<>() { @Override public ZoneId queryFrom(TemporalAccessor temporal) { return temporal.query(TemporalQueries.ZONE_ID); } @Override public String toString() { return "ZoneId"; } }; /** * A query for the {@code Chronology}. */ static final TemporalQuery<Chronology> CHRONO = new TemporalQuery<>() { @Override public Chronology queryFrom(TemporalAccessor temporal) { return temporal.query(TemporalQueries.CHRONO); } @Override public String toString() { return "Chronology"; } }; /** * A query for the smallest supported unit. */ static final TemporalQuery<TemporalUnit> PRECISION = new TemporalQuery<>() { @Override public TemporalUnit queryFrom(TemporalAccessor temporal) { return temporal.query(TemporalQueries.PRECISION); } @Override public String toString() { return "Precision"; } }; //----------------------------------------------------------------------- /** * A query for {@code ZoneOffset} returning null if not found. */ static final TemporalQuery<ZoneOffset> OFFSET = new TemporalQuery<>() { @Override public ZoneOffset queryFrom(TemporalAccessor temporal) { if (temporal.isSupported(OFFSET_SECONDS)) { return ZoneOffset.ofTotalSeconds(temporal.get(OFFSET_SECONDS)); } return null; } @Override public String toString() { return "ZoneOffset"; } }; /** * A lenient query for the {@code ZoneId}, falling back to the {@code ZoneOffset}. */ static final TemporalQuery<ZoneId> ZONE = new TemporalQuery<>() { @Override public ZoneId queryFrom(TemporalAccessor temporal) { ZoneId zone = temporal.query(ZONE_ID); return (zone != null ? zone : temporal.query(OFFSET)); } @Override public String toString() { return "Zone"; } }; /** * A query for {@code LocalDate} returning null if not found. */ static final TemporalQuery<LocalDate> LOCAL_DATE = new TemporalQuery<>() { @Override public LocalDate queryFrom(TemporalAccessor temporal) { if (temporal.isSupported(EPOCH_DAY)) { return LocalDate.ofEpochDay(temporal.getLong(EPOCH_DAY)); } return null; } @Override public String toString() { return "LocalDate"; } }; /** * A query for {@code LocalTime} returning null if not found. */ static final TemporalQuery<LocalTime> LOCAL_TIME = new TemporalQuery<>() { @Override public LocalTime queryFrom(TemporalAccessor temporal) { if (temporal.isSupported(NANO_OF_DAY)) { return LocalTime.ofNanoOfDay(temporal.getLong(NANO_OF_DAY)); } return null; } @Override public String toString() { return "LocalTime"; } }; }