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/*

 * 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) 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:

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 *  * Redistributions of source code must retain the above copyright notice,

 *    this list of conditions and the following disclaimer.

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 */

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);

}