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399 lines
16 KiB
399 lines
16 KiB
/*
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* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
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* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*
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*/
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/*
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*
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*
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*
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*
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*
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* Copyright (c) 2007-2012, Stephen Colebourne & Michael Nascimento Santos
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*
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* * Redistributions of source code must retain the above copyright notice,
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* this list of conditions and the following disclaimer.
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*
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* * Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* * Neither the name of JSR-310 nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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package java.time.temporal;
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import static java.time.temporal.ChronoField.EPOCH_DAY;
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import static java.time.temporal.ChronoField.NANO_OF_DAY;
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import static java.time.temporal.ChronoField.OFFSET_SECONDS;
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import java.time.LocalDate;
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import java.time.LocalTime;
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import java.time.ZoneId;
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import java.time.ZoneOffset;
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import java.time.chrono.Chronology;
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/**
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* Common implementations of {@code TemporalQuery}.
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* <p>
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* This class provides common implementations of {@link TemporalQuery}.
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* These are defined here as they must be constants, and the definition
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* of lambdas does not guarantee that. By assigning them once here,
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* they become 'normal' Java constants.
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* <p>
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* Queries are a key tool for extracting information from temporal objects.
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* They exist to externalize the process of querying, permitting different
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* approaches, as per the strategy design pattern.
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* Examples might be a query that checks if the date is the day before February 29th
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* in a leap year, or calculates the number of days to your next birthday.
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* <p>
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* The {@link TemporalField} interface provides another mechanism for querying
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* temporal objects. That interface is limited to returning a {@code long}.
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* By contrast, queries can return any type.
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* <p>
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* There are two equivalent ways of using a {@code TemporalQuery}.
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* The first is to invoke the method on this interface directly.
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* The second is to use {@link TemporalAccessor#query(TemporalQuery)}:
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* <pre>
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* // these two lines are equivalent, but the second approach is recommended
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* temporal = thisQuery.queryFrom(temporal);
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* temporal = temporal.query(thisQuery);
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* </pre>
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* It is recommended to use the second approach, {@code query(TemporalQuery)},
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* as it is a lot clearer to read in code.
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* <p>
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* The most common implementations are method references, such as
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* {@code LocalDate::from} and {@code ZoneId::from}.
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* Additional common queries are provided to return:
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* <ul>
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* <li> a Chronology,
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* <li> a LocalDate,
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* <li> a LocalTime,
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* <li> a ZoneOffset,
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* <li> a precision,
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* <li> a zone, or
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* <li> a zoneId.
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* </ul>
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*
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* @since 1.8
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*/
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public final class TemporalQueries {
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// note that it is vital that each method supplies a constant, not a
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// calculated value, as they will be checked for using ==
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// it is also vital that each constant is different (due to the == checking)
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// as such, alterations to this code must be done with care
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/**
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* Private constructor since this is a utility class.
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*/
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private TemporalQueries() {
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}
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//-----------------------------------------------------------------------
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// special constants should be used to extract information from a TemporalAccessor
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// that cannot be derived in other ways
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// Javadoc added here, so as to pretend they are more normal than they really are
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/**
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* A strict query for the {@code ZoneId}.
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* <p>
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* This queries a {@code TemporalAccessor} for the zone.
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* The zone is only returned if the date-time conceptually contains a {@code ZoneId}.
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* It will not be returned if the date-time only conceptually has an {@code ZoneOffset}.
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* Thus a {@link java.time.ZonedDateTime} will return the result of {@code getZone()},
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* but an {@link java.time.OffsetDateTime} will return null.
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* <p>
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* In most cases, applications should use {@link #zone()} as this query is too strict.
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* <p>
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* The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>
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* {@code LocalDate} returns null<br>
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* {@code LocalTime} returns null<br>
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* {@code LocalDateTime} returns null<br>
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* {@code ZonedDateTime} returns the associated zone<br>
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* {@code OffsetTime} returns null<br>
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* {@code OffsetDateTime} returns null<br>
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* {@code ChronoLocalDate} returns null<br>
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* {@code ChronoLocalDateTime} returns null<br>
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* {@code ChronoZonedDateTime} returns the associated zone<br>
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* {@code Era} returns null<br>
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* {@code DayOfWeek} returns null<br>
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* {@code Month} returns null<br>
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* {@code Year} returns null<br>
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* {@code YearMonth} returns null<br>
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* {@code MonthDay} returns null<br>
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* {@code ZoneOffset} returns null<br>
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* {@code Instant} returns null<br>
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*
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* @return a query that can obtain the zone ID of a temporal, not null
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*/
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public static TemporalQuery<ZoneId> zoneId() {
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return TemporalQueries.ZONE_ID;
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}
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/**
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* A query for the {@code Chronology}.
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* <p>
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* This queries a {@code TemporalAccessor} for the chronology.
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* If the target {@code TemporalAccessor} represents a date, or part of a date,
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* then it should return the chronology that the date is expressed in.
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* As a result of this definition, objects only representing time, such as
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* {@code LocalTime}, will return null.
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* <p>
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* The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>
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* {@code LocalDate} returns {@code IsoChronology.INSTANCE}<br>
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* {@code LocalTime} returns null (does not represent a date)<br>
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* {@code LocalDateTime} returns {@code IsoChronology.INSTANCE}<br>
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* {@code ZonedDateTime} returns {@code IsoChronology.INSTANCE}<br>
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* {@code OffsetTime} returns null (does not represent a date)<br>
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* {@code OffsetDateTime} returns {@code IsoChronology.INSTANCE}<br>
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* {@code ChronoLocalDate} returns the associated chronology<br>
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* {@code ChronoLocalDateTime} returns the associated chronology<br>
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* {@code ChronoZonedDateTime} returns the associated chronology<br>
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* {@code Era} returns the associated chronology<br>
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* {@code DayOfWeek} returns null (shared across chronologies)<br>
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* {@code Month} returns {@code IsoChronology.INSTANCE}<br>
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* {@code Year} returns {@code IsoChronology.INSTANCE}<br>
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* {@code YearMonth} returns {@code IsoChronology.INSTANCE}<br>
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* {@code MonthDay} returns null {@code IsoChronology.INSTANCE}<br>
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* {@code ZoneOffset} returns null (does not represent a date)<br>
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* {@code Instant} returns null (does not represent a date)<br>
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* <p>
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* The method {@link java.time.chrono.Chronology#from(TemporalAccessor)} can be used as a
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* {@code TemporalQuery} via a method reference, {@code Chronology::from}.
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* That method is equivalent to this query, except that it throws an
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* exception if a chronology cannot be obtained.
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*
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* @return a query that can obtain the chronology of a temporal, not null
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*/
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public static TemporalQuery<Chronology> chronology() {
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return TemporalQueries.CHRONO;
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}
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/**
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* A query for the smallest supported unit.
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* <p>
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* This queries a {@code TemporalAccessor} for the time precision.
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* If the target {@code TemporalAccessor} represents a consistent or complete date-time,
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* date or time then this must return the smallest precision actually supported.
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* Note that fields such as {@code NANO_OF_DAY} and {@code NANO_OF_SECOND}
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* are defined to always return ignoring the precision, thus this is the only
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* way to find the actual smallest supported unit.
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* For example, were {@code GregorianCalendar} to implement {@code TemporalAccessor}
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* it would return a precision of {@code MILLIS}.
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* <p>
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* The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>
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* {@code LocalDate} returns {@code DAYS}<br>
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* {@code LocalTime} returns {@code NANOS}<br>
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* {@code LocalDateTime} returns {@code NANOS}<br>
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* {@code ZonedDateTime} returns {@code NANOS}<br>
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* {@code OffsetTime} returns {@code NANOS}<br>
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* {@code OffsetDateTime} returns {@code NANOS}<br>
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* {@code ChronoLocalDate} returns {@code DAYS}<br>
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* {@code ChronoLocalDateTime} returns {@code NANOS}<br>
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* {@code ChronoZonedDateTime} returns {@code NANOS}<br>
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* {@code Era} returns {@code ERAS}<br>
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* {@code DayOfWeek} returns {@code DAYS}<br>
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* {@code Month} returns {@code MONTHS}<br>
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* {@code Year} returns {@code YEARS}<br>
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* {@code YearMonth} returns {@code MONTHS}<br>
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* {@code MonthDay} returns null (does not represent a complete date or time)<br>
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* {@code ZoneOffset} returns null (does not represent a date or time)<br>
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* {@code Instant} returns {@code NANOS}<br>
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*
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* @return a query that can obtain the precision of a temporal, not null
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*/
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public static TemporalQuery<TemporalUnit> precision() {
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return TemporalQueries.PRECISION;
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}
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//-----------------------------------------------------------------------
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// non-special constants are standard queries that derive information from other information
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/**
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* A lenient query for the {@code ZoneId}, falling back to the {@code ZoneOffset}.
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* <p>
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* This queries a {@code TemporalAccessor} for the zone.
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* It first tries to obtain the zone, using {@link #zoneId()}.
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* If that is not found it tries to obtain the {@link #offset()}.
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* Thus a {@link java.time.ZonedDateTime} will return the result of {@code getZone()},
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* while an {@link java.time.OffsetDateTime} will return the result of {@code getOffset()}.
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* <p>
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* In most cases, applications should use this query rather than {@code #zoneId()}.
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* <p>
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* The method {@link ZoneId#from(TemporalAccessor)} can be used as a
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* {@code TemporalQuery} via a method reference, {@code ZoneId::from}.
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* That method is equivalent to this query, except that it throws an
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* exception if a zone cannot be obtained.
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*
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* @return a query that can obtain the zone ID or offset of a temporal, not null
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*/
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public static TemporalQuery<ZoneId> zone() {
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return TemporalQueries.ZONE;
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}
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/**
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* A query for {@code ZoneOffset} returning null if not found.
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* <p>
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* This returns a {@code TemporalQuery} that can be used to query a temporal
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* object for the offset. The query will return null if the temporal
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* object cannot supply an offset.
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* <p>
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* The query implementation examines the {@link ChronoField#OFFSET_SECONDS OFFSET_SECONDS}
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* field and uses it to create a {@code ZoneOffset}.
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* <p>
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* The method {@link java.time.ZoneOffset#from(TemporalAccessor)} can be used as a
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* {@code TemporalQuery} via a method reference, {@code ZoneOffset::from}.
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* This query and {@code ZoneOffset::from} will return the same result if the
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* temporal object contains an offset. If the temporal object does not contain
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* an offset, then the method reference will throw an exception, whereas this
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* query will return null.
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*
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* @return a query that can obtain the offset of a temporal, not null
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*/
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public static TemporalQuery<ZoneOffset> offset() {
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return TemporalQueries.OFFSET;
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}
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/**
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* A query for {@code LocalDate} returning null if not found.
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* <p>
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* This returns a {@code TemporalQuery} that can be used to query a temporal
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* object for the local date. The query will return null if the temporal
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* object cannot supply a local date.
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* <p>
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* The query implementation examines the {@link ChronoField#EPOCH_DAY EPOCH_DAY}
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* field and uses it to create a {@code LocalDate}.
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* <p>
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* The method {@link ZoneOffset#from(TemporalAccessor)} can be used as a
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* {@code TemporalQuery} via a method reference, {@code LocalDate::from}.
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* This query and {@code LocalDate::from} will return the same result if the
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* temporal object contains a date. If the temporal object does not contain
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* a date, then the method reference will throw an exception, whereas this
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* query will return null.
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*
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* @return a query that can obtain the date of a temporal, not null
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*/
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public static TemporalQuery<LocalDate> localDate() {
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return TemporalQueries.LOCAL_DATE;
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}
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/**
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* A query for {@code LocalTime} returning null if not found.
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* <p>
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* This returns a {@code TemporalQuery} that can be used to query a temporal
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* object for the local time. The query will return null if the temporal
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* object cannot supply a local time.
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* <p>
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* The query implementation examines the {@link ChronoField#NANO_OF_DAY NANO_OF_DAY}
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* field and uses it to create a {@code LocalTime}.
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* <p>
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* The method {@link ZoneOffset#from(TemporalAccessor)} can be used as a
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* {@code TemporalQuery} via a method reference, {@code LocalTime::from}.
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* This query and {@code LocalTime::from} will return the same result if the
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* temporal object contains a time. If the temporal object does not contain
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* a time, then the method reference will throw an exception, whereas this
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* query will return null.
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*
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* @return a query that can obtain the time of a temporal, not null
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*/
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public static TemporalQuery<LocalTime> localTime() {
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return TemporalQueries.LOCAL_TIME;
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}
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//-----------------------------------------------------------------------
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/**
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* A strict query for the {@code ZoneId}.
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*/
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static final TemporalQuery<ZoneId> ZONE_ID = (temporal) ->
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temporal.query(TemporalQueries.ZONE_ID);
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/**
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* A query for the {@code Chronology}.
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*/
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static final TemporalQuery<Chronology> CHRONO = (temporal) ->
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temporal.query(TemporalQueries.CHRONO);
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/**
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* A query for the smallest supported unit.
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*/
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static final TemporalQuery<TemporalUnit> PRECISION = (temporal) ->
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temporal.query(TemporalQueries.PRECISION);
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//-----------------------------------------------------------------------
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/**
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* A query for {@code ZoneOffset} returning null if not found.
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*/
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static final TemporalQuery<ZoneOffset> OFFSET = (temporal) -> {
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if (temporal.isSupported(OFFSET_SECONDS)) {
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return ZoneOffset.ofTotalSeconds(temporal.get(OFFSET_SECONDS));
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}
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return null;
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};
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/**
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* A lenient query for the {@code ZoneId}, falling back to the {@code ZoneOffset}.
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*/
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static final TemporalQuery<ZoneId> ZONE = (temporal) -> {
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ZoneId zone = temporal.query(ZONE_ID);
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return (zone != null ? zone : temporal.query(OFFSET));
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};
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/**
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* A query for {@code LocalDate} returning null if not found.
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*/
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static final TemporalQuery<LocalDate> LOCAL_DATE = (temporal) -> {
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if (temporal.isSupported(EPOCH_DAY)) {
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return LocalDate.ofEpochDay(temporal.getLong(EPOCH_DAY));
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}
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return null;
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};
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/**
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* A query for {@code LocalTime} returning null if not found.
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*/
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static final TemporalQuery<LocalTime> LOCAL_TIME = (temporal) -> {
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if (temporal.isSupported(NANO_OF_DAY)) {
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return LocalTime.ofNanoOfDay(temporal.getLong(NANO_OF_DAY));
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}
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return null;
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};
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}
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