/* * 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}. *

* 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. *

* 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. *

* 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. *

* 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)}: *

 *   // these two lines are equivalent, but the second approach is recommended
 *   temporal = thisQuery.queryFrom(temporal);
 *   temporal = temporal.query(thisQuery);
 * 
* It is recommended to use the second approach, {@code query(TemporalQuery)}, * as it is a lot clearer to read in code. *

* The most common implementations are method references, such as * {@code LocalDate::from} and {@code ZoneId::from}. * Additional common queries are provided to return: *

* * @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}. *

* 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. *

* In most cases, applications should use {@link #zone()} as this query is too strict. *

* The result from JDK classes implementing {@code TemporalAccessor} is as follows:
* {@code LocalDate} returns null
* {@code LocalTime} returns null
* {@code LocalDateTime} returns null
* {@code ZonedDateTime} returns the associated zone
* {@code OffsetTime} returns null
* {@code OffsetDateTime} returns null
* {@code ChronoLocalDate} returns null
* {@code ChronoLocalDateTime} returns null
* {@code ChronoZonedDateTime} returns the associated zone
* {@code Era} returns null
* {@code DayOfWeek} returns null
* {@code Month} returns null
* {@code Year} returns null
* {@code YearMonth} returns null
* {@code MonthDay} returns null
* {@code ZoneOffset} returns null
* {@code Instant} returns null
* * @return a query that can obtain the zone ID of a temporal, not null */ public static TemporalQuery zoneId() { return TemporalQueries.ZONE_ID; } /** * A query for the {@code Chronology}. *

* 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. *

* The result from JDK classes implementing {@code TemporalAccessor} is as follows:
* {@code LocalDate} returns {@code IsoChronology.INSTANCE}
* {@code LocalTime} returns null (does not represent a date)
* {@code LocalDateTime} returns {@code IsoChronology.INSTANCE}
* {@code ZonedDateTime} returns {@code IsoChronology.INSTANCE}
* {@code OffsetTime} returns null (does not represent a date)
* {@code OffsetDateTime} returns {@code IsoChronology.INSTANCE}
* {@code ChronoLocalDate} returns the associated chronology
* {@code ChronoLocalDateTime} returns the associated chronology
* {@code ChronoZonedDateTime} returns the associated chronology
* {@code Era} returns the associated chronology
* {@code DayOfWeek} returns null (shared across chronologies)
* {@code Month} returns {@code IsoChronology.INSTANCE}
* {@code Year} returns {@code IsoChronology.INSTANCE}
* {@code YearMonth} returns {@code IsoChronology.INSTANCE}
* {@code MonthDay} returns null {@code IsoChronology.INSTANCE}
* {@code ZoneOffset} returns null (does not represent a date)
* {@code Instant} returns null (does not represent a date)
*

* 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() { return TemporalQueries.CHRONO; } /** * A query for the smallest supported unit. *

* 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}. *

* The result from JDK classes implementing {@code TemporalAccessor} is as follows:
* {@code LocalDate} returns {@code DAYS}
* {@code LocalTime} returns {@code NANOS}
* {@code LocalDateTime} returns {@code NANOS}
* {@code ZonedDateTime} returns {@code NANOS}
* {@code OffsetTime} returns {@code NANOS}
* {@code OffsetDateTime} returns {@code NANOS}
* {@code ChronoLocalDate} returns {@code DAYS}
* {@code ChronoLocalDateTime} returns {@code NANOS}
* {@code ChronoZonedDateTime} returns {@code NANOS}
* {@code Era} returns {@code ERAS}
* {@code DayOfWeek} returns {@code DAYS}
* {@code Month} returns {@code MONTHS}
* {@code Year} returns {@code YEARS}
* {@code YearMonth} returns {@code MONTHS}
* {@code MonthDay} returns null (does not represent a complete date or time)
* {@code ZoneOffset} returns null (does not represent a date or time)
* {@code Instant} returns {@code NANOS}
* * @return a query that can obtain the precision of a temporal, not null */ public static TemporalQuery 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}. *

* 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()}. *

* In most cases, applications should use this query rather than {@code #zoneId()}. *

* 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 zone() { return TemporalQueries.ZONE; } /** * A query for {@code ZoneOffset} returning null if not found. *

* 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. *

* The query implementation examines the {@link ChronoField#OFFSET_SECONDS OFFSET_SECONDS} * field and uses it to create a {@code ZoneOffset}. *

* 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 offset() { return TemporalQueries.OFFSET; } /** * A query for {@code LocalDate} returning null if not found. *

* 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. *

* The query implementation examines the {@link ChronoField#EPOCH_DAY EPOCH_DAY} * field and uses it to create a {@code LocalDate}. *

* 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() { return TemporalQueries.LOCAL_DATE; } /** * A query for {@code LocalTime} returning null if not found. *

* 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. *

* The query implementation examines the {@link ChronoField#NANO_OF_DAY NANO_OF_DAY} * field and uses it to create a {@code LocalTime}. *

* 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() { return TemporalQueries.LOCAL_TIME; } //----------------------------------------------------------------------- /** * A strict query for the {@code ZoneId}. */ static final TemporalQuery ZONE_ID = (temporal) -> temporal.query(TemporalQueries.ZONE_ID); /** * A query for the {@code Chronology}. */ static final TemporalQuery CHRONO = (temporal) -> temporal.query(TemporalQueries.CHRONO); /** * A query for the smallest supported unit. */ static final TemporalQuery PRECISION = (temporal) -> temporal.query(TemporalQueries.PRECISION); //----------------------------------------------------------------------- /** * A query for {@code ZoneOffset} returning null if not found. */ static final TemporalQuery OFFSET = (temporal) -> { if (temporal.isSupported(OFFSET_SECONDS)) { return ZoneOffset.ofTotalSeconds(temporal.get(OFFSET_SECONDS)); } return null; }; /** * A lenient query for the {@code ZoneId}, falling back to the {@code ZoneOffset}. */ static final TemporalQuery ZONE = (temporal) -> { ZoneId zone = temporal.query(ZONE_ID); return (zone != null ? zone : temporal.query(OFFSET)); }; /** * A query for {@code LocalDate} returning null if not found. */ static final TemporalQuery LOCAL_DATE = (temporal) -> { if (temporal.isSupported(EPOCH_DAY)) { return LocalDate.ofEpochDay(temporal.getLong(EPOCH_DAY)); } return null; }; /** * A query for {@code LocalTime} returning null if not found. */ static final TemporalQuery LOCAL_TIME = (temporal) -> { if (temporal.isSupported(NANO_OF_DAY)) { return LocalTime.ofNanoOfDay(temporal.getLong(NANO_OF_DAY)); } return null; }; }