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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

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package java.time.temporal;

import java.time.DateTimeException;

import java.time.LocalDate;

import java.time.LocalTime;

import java.time.ZoneId;

import java.time.ZoneOffset;

import java.time.chrono.Chronology;

/**

 * 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 implementations are provided on this interface as static methods.

 *

 * This interface places no restrictions on the mutability of implementations,

 * however immutability is strongly recommended.

 *

 * @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.

     *

     * 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 TemporalQuery#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);

    //-----------------------------------------------------------------------

    // special constants should be used to extract information from a TemporalAccessor

    // that cannot be derived in other ways

    // Javadoc added here, so as to pretend they are more normal than they really are

    /**

     * A strict query for the {@code ZoneId}.

     * <p>

     * This queries a {@code TemporalAccessor} for the zone.

     * The zone is only returned if the date-time conceptually contains a {@code ZoneId}.

     * It will not be returned if the date-time only conceptually has an {@code ZoneOffset}.

     * Thus a {@link java.time.ZonedDateTime} will return the result of {@code getZone()},

     * but an {@link java.time.OffsetDateTime} will return null.

     * <p>

     * In most cases, applications should use {@link #zone()} as this query is too strict.

     * <p>

     * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>

     * {@code LocalDate} returns null<br>

     * {@code LocalTime} returns null<br>

     * {@code LocalDateTime} returns null<br>

     * {@code ZonedDateTime} returns the associated zone<br>

     * {@code OffsetTime} returns null<br>

     * {@code OffsetDateTime} returns null<br>

     * {@code ChronoLocalDate} returns null<br>

     * {@code ChronoLocalDateTime} returns null<br>

     * {@code ChronoZonedDateTime} returns the associated zone<br>

     * {@code Era} returns null<br>

     * {@code DayOfWeek} returns null<br>

     * {@code Month} returns null<br>

     * {@code Year} returns null<br>

     * {@code YearMonth} returns null<br>

     * {@code MonthDay} returns null<br>

     * {@code ZoneOffset} returns null<br>

     * {@code Instant} returns null<br>

     *

     * @return a query that can obtain the zone ID of a temporal, not null

     */

    static TemporalQuery<ZoneId> zoneId() {

        return TemporalQueries.ZONE_ID;

    }

    /**

     * A query for the {@code Chronology}.

     * <p>

     * This queries a {@code TemporalAccessor} for the chronology.

     * If the target {@code TemporalAccessor} represents a date, or part of a date,

     * then it should return the chronology that the date is expressed in.

     * As a result of this definition, objects only representing time, such as

     * {@code LocalTime}, will return null.

     * <p>

     * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>

     * {@code LocalDate} returns {@code IsoChronology.INSTANCE}<br>

     * {@code LocalTime} returns null (does not represent a date)<br>

     * {@code LocalDateTime} returns {@code IsoChronology.INSTANCE}<br>

     * {@code ZonedDateTime} returns {@code IsoChronology.INSTANCE}<br>

     * {@code OffsetTime} returns null (does not represent a date)<br>

     * {@code OffsetDateTime} returns {@code IsoChronology.INSTANCE}<br>

     * {@code ChronoLocalDate} returns the associated chronology<br>

     * {@code ChronoLocalDateTime} returns the associated chronology<br>

     * {@code ChronoZonedDateTime} returns the associated chronology<br>

     * {@code Era} returns the associated chronology<br>

     * {@code DayOfWeek} returns null (shared across chronologies)<br>

     * {@code Month} returns {@code IsoChronology.INSTANCE}<br>

     * {@code Year} returns {@code IsoChronology.INSTANCE}<br>

     * {@code YearMonth} returns {@code IsoChronology.INSTANCE}<br>

     * {@code MonthDay} returns null {@code IsoChronology.INSTANCE}<br>

     * {@code ZoneOffset} returns null (does not represent a date)<br>

     * {@code Instant} returns null (does not represent a date)<br>

     * <p>

     * The method {@link java.time.chrono.Chronology#from(TemporalAccessor)} can be used as a

     * {@code TemporalQuery} via a method reference, {@code Chronology::from}.

     * That method is equivalent to this query, except that it throws an

     * exception if a chronology cannot be obtained.

     *

     * @return a query that can obtain the chronology of a temporal, not null

     */

    static TemporalQuery<Chronology> chronology() {

        return TemporalQueries.CHRONO;

    }

    /**

     * A query for the smallest supported unit.

     * <p>

     * This queries a {@code TemporalAccessor} for the time precision.

     * If the target {@code TemporalAccessor} represents a consistent or complete date-time,

     * date or time then this must return the smallest precision actually supported.

     * Note that fields such as {@code NANO_OF_DAY} and {@code NANO_OF_SECOND}

     * are defined to always return ignoring the precision, thus this is the only

     * way to find the actual smallest supported unit.

     * For example, were {@code GregorianCalendar} to implement {@code TemporalAccessor}

     * it would return a precision of {@code MILLIS}.

     * <p>

     * The result from JDK classes implementing {@code TemporalAccessor} is as follows:<br>

     * {@code LocalDate} returns {@code DAYS}<br>

     * {@code LocalTime} returns {@code NANOS}<br>

     * {@code LocalDateTime} returns {@code NANOS}<br>

     * {@code ZonedDateTime} returns {@code NANOS}<br>

     * {@code OffsetTime} returns {@code NANOS}<br>

     * {@code OffsetDateTime} returns {@code NANOS}<br>

     * {@code ChronoLocalDate} returns {@code DAYS}<br>

     * {@code ChronoLocalDateTime} returns {@code NANOS}<br>

     * {@code ChronoZonedDateTime} returns {@code NANOS}<br>

     * {@code Era} returns {@code ERAS}<br>

     * {@code DayOfWeek} returns {@code DAYS}<br>

     * {@code Month} returns {@code MONTHS}<br>

     * {@code Year} returns {@code YEARS}<br>

     * {@code YearMonth} returns {@code MONTHS}<br>

     * {@code MonthDay} returns null (does not represent a complete date or time)<br>

     * {@code ZoneOffset} returns null (does not represent a date or time)<br>

     * {@code Instant} returns {@code NANOS}<br>

     *

     * @return a query that can obtain the precision of a temporal, not null

     */

    static TemporalQuery<TemporalUnit> precision() {

        return TemporalQueries.PRECISION;

    }

    //-----------------------------------------------------------------------

    // non-special constants are standard queries that derive information from other information

    /**

     * A lenient query for the {@code ZoneId}, falling back to the {@code ZoneOffset}.

     * <p>

     * This queries a {@code TemporalAccessor} for the zone.

     * It first tries to obtain the zone, using {@link #zoneId()}.

     * If that is not found it tries to obtain the {@link #offset()}.

     * Thus a {@link java.time.ZonedDateTime} will return the result of {@code getZone()},

     * while an {@link java.time.OffsetDateTime} will return the result of {@code getOffset()}.

     * <p>

     * In most cases, applications should use this query rather than {@code #zoneId()}.

     * <p>

     * The method {@link ZoneId#from(TemporalAccessor)} can be used as a

     * {@code TemporalQuery} via a method reference, {@code ZoneId::from}.

     * That method is equivalent to this query, except that it throws an

     * exception if a zone cannot be obtained.

     *

     * @return a query that can obtain the zone ID or offset of a temporal, not null

     */

    static TemporalQuery<ZoneId> zone() {

        return TemporalQueries.ZONE;

    }

    /**

     * A query for {@code ZoneOffset} returning null if not found.

     * <p>

     * This returns a {@code TemporalQuery} that can be used to query a temporal

     * object for the offset. The query will return null if the temporal

     * object cannot supply an offset.

     * <p>

     * The query implementation examines the {@link ChronoField#OFFSET_SECONDS OFFSET_SECONDS}

     * field and uses it to create a {@code ZoneOffset}.

     * <p>

     * The method {@link java.time.ZoneOffset#from(TemporalAccessor)} can be used as a

     * {@code TemporalQuery} via a method reference, {@code ZoneOffset::from}.

     * This query and {@code ZoneOffset::from} will return the same result if the

     * temporal object contains an offset. If the temporal object does not contain

     * an offset, then the method reference will throw an exception, whereas this

     * query will return null.

     *

     * @return a query that can obtain the offset of a temporal, not null

     */

    static TemporalQuery<ZoneOffset> offset() {

        return TemporalQueries.OFFSET;

    }

    /**

     * A query for {@code LocalDate} returning null if not found.

     * <p>

     * This returns a {@code TemporalQuery} that can be used to query a temporal

     * object for the local date. The query will return null if the temporal

     * object cannot supply a local date.

     * <p>

     * The query implementation examines the {@link ChronoField#EPOCH_DAY EPOCH_DAY}

     * field and uses it to create a {@code LocalDate}.

     * <p>

     * The method {@link ZoneOffset#from(TemporalAccessor)} can be used as a

     * {@code TemporalQuery} via a method reference, {@code LocalDate::from}.

     * This query and {@code LocalDate::from} will return the same result if the

     * temporal object contains a date. If the temporal object does not contain

     * a date, then the method reference will throw an exception, whereas this

     * query will return null.

     *

     * @return a query that can obtain the date of a temporal, not null

     */

    static TemporalQuery<LocalDate> localDate() {

        return TemporalQueries.LOCAL_DATE;

    }

    /**

     * A query for {@code LocalTime} returning null if not found.

     * <p>

     * This returns a {@code TemporalQuery} that can be used to query a temporal

     * object for the local time. The query will return null if the temporal

     * object cannot supply a local time.

     * <p>

     * The query implementation examines the {@link ChronoField#NANO_OF_DAY NANO_OF_DAY}

     * field and uses it to create a {@code LocalTime}.

     * <p>

     * The method {@link ZoneOffset#from(TemporalAccessor)} can be used as a

     * {@code TemporalQuery} via a method reference, {@code LocalTime::from}.

     * This query and {@code LocalTime::from} will return the same result if the

     * temporal object contains a time. If the temporal object does not contain

     * a time, then the method reference will throw an exception, whereas this

     * query will return null.

     *

     * @return a query that can obtain the time of a temporal, not null

     */

    static TemporalQuery<LocalTime> localTime() {

        return TemporalQueries.LOCAL_TIME;

    }

}