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Backport of JSR-310 from JDK 8 to JDK 7 and JDK 6. NOT an implementation of the JSR.

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/*
 * Copyright (c) 2007-present, Stephen Colebourne & Michael Nascimento Santos
 *
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package org.threeten.bp.temporal;

import org.threeten.bp.DateTimeException;

/**
 * Strategy for querying a temporal object.
 * 

* 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}. * Further implementations are on {@link TemporalQueries}. * Queries may also be defined by applications. * *

Specification for implementors

* This interface places no restrictions on the mutability of implementations, * however immutability is strongly recommended. */ public interface TemporalQuery { /** * Queries the specified temporal object. *

* 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. *

* 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)}: *

     *   // 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. * *

Specification for implementors

* 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. *

* 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}. *

* 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); }





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