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TemporalQuery.java
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145 lines (140 loc) · 5.36 KB
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/*
* Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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/*
*
*
*
*
*
* Copyright (c) 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 java.time.DateTimeException;
/**
* Strategy for querying a temporal object.
* <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 as static methods in {@link TemporalQueries}.
*
* @implSpec
* This interface places no restrictions on the mutability of implementations,
* however immutability is strongly recommended.
*
* @param <R> the type returned from the query
*
* @since 1.8
*/
@FunctionalInterface
public interface TemporalQuery<R> {
/**
* Queries the specified temporal object.
* <p>
* This queries the specified temporal object to return an object using the logic
* encapsulated in the implementing class.
* 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>
* There are two equivalent ways of using this method.
* The first is to invoke this method 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.
*
* @implSpec
* The implementation must take the input object and query it.
* The implementation defines the logic of the query and is responsible for
* documenting that logic.
* It may use any method on {@code TemporalAccessor} to determine the result.
* The input object must not be altered.
* <p>
* The input temporal object may be in a calendar system other than ISO.
* Implementations may choose to document compatibility with other calendar systems,
* or reject non-ISO temporal objects by {@link TemporalQueries#chronology() querying the chronology}.
* <p>
* This method may be called from multiple threads in parallel.
* It must be thread-safe when invoked.
*
* @param temporal the temporal object to query, not null
* @return the queried value, may return null to indicate not found
* @throws DateTimeException if unable to query
* @throws ArithmeticException if numeric overflow occurs
*/
R queryFrom(TemporalAccessor temporal);
}