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146 lines
5.4 KiB
146 lines
5.4 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) 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 java.time.DateTimeException;
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/**
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* Strategy for querying a temporal object.
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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 as static methods in {@link TemporalQueries}.
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*
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* @implSpec
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* This interface places no restrictions on the mutability of implementations,
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* however immutability is strongly recommended.
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*
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* @param <R> the type returned from the query
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*
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* @since 1.8
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*/
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@FunctionalInterface
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public interface TemporalQuery<R> {
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/**
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* Queries the specified temporal object.
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* <p>
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* This queries the specified temporal object to return an object using the logic
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* encapsulated in the implementing class.
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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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* There are two equivalent ways of using this method.
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* The first is to invoke this method 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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*
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* @implSpec
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* The implementation must take the input object and query it.
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* The implementation defines the logic of the query and is responsible for
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* documenting that logic.
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* It may use any method on {@code TemporalAccessor} to determine the result.
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* The input object must not be altered.
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* <p>
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* The input temporal object may be in a calendar system other than ISO.
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* Implementations may choose to document compatibility with other calendar systems,
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* or reject non-ISO temporal objects by {@link TemporalQueries#chronology() querying the chronology}.
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* <p>
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* This method may be called from multiple threads in parallel.
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* It must be thread-safe when invoked.
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*
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* @param temporal the temporal object to query, not null
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* @return the queried value, may return null to indicate not found
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* @throws DateTimeException if unable to query
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* @throws ArithmeticException if numeric overflow occurs
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*/
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R queryFrom(TemporalAccessor temporal);
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}
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