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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.

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package java.time.temporal;

import java.time.DateTimeException;

import java.time.format.DateTimeBuilder;

import java.util.Comparator;

/**

 * A field of date-time, such as month-of-year or hour-of-minute.

 * <p>

 * Date and time is expressed using fields which partition the time-line into something

 * meaningful for humans. Implementations of this interface represent those fields.

 * <p>

 * The most commonly used units are defined in {@link ChronoField}.

 * Further fields are supplied in {@link ISOFields}, {@link WeekFields} and {@link JulianFields}.

 * Fields can also be written by application code by implementing this interface.

 * <p>

 * The field works using double dispatch. Client code calls methods on a date-time like

 * {@code LocalDateTime} which check if the field is a {@code ChronoField}.

 * If it is, then the date-time must handle it.

 * Otherwise, the method call is re-dispatched to the matching method in this interface.

 *

 * <h3>Specification for implementors</h3>

 * This interface must be implemented with care to ensure other classes operate correctly.

 * All implementations that can be instantiated must be final, immutable and thread-safe.

 * It is recommended to use an enum where possible.

 *

 * @since 1.8

 */

public interface TemporalField extends Comparator<TemporalAccessor> {

    /**

     * Gets a descriptive name for the field.

     * <p>

     * The should be of the format 'BaseOfRange', such as 'MonthOfYear',

     * unless the field has a range of {@code FOREVER}, when only

     * the base unit is mentioned, such as 'Year' or 'Era'.

     *

     * @return the name, not null

     */

    String getName();

    /**

     * Gets the unit that the field is measured in.

     * <p>

     * The unit of the field is the period that varies within the range.

     * For example, in the field 'MonthOfYear', the unit is 'Months'.

     * See also {@link #getRangeUnit()}.

     *

     * @return the period unit defining the base unit of the field, not null

     */

    TemporalUnit getBaseUnit();

    /**

     * Gets the range that the field is bound by.

     * <p>

     * The range of the field is the period that the field varies within.

     * For example, in the field 'MonthOfYear', the range is 'Years'.

     * See also {@link #getBaseUnit()}.

     * <p>

     * The range is never null. For example, the 'Year' field is shorthand for

     * 'YearOfForever'. It therefore has a unit of 'Years' and a range of 'Forever'.

     *

     * @return the period unit defining the range of the field, not null

     */

    TemporalUnit getRangeUnit();

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

    /**

     * Compares the value of this field in two temporal objects.

     * <p>

     * All fields implement {@link Comparator} on {@link TemporalAccessor}.

     * This allows a list of date-times to be compared using the value of a field.

     * For example, you could sort a list of arbitrary temporal objects by the value of

     * the month-of-year field - {@code Collections.sort(list, MONTH_OF_YEAR)}

     * <p>

     * The default implementation must behave equivalent to this code:

     * <pre>

     *  return Long.compare(temporal1.getLong(this), temporal2.getLong(this));

     * </pre>

     *

     * @param temporal1  the first temporal object to compare, not null

     * @param temporal2  the second temporal object to compare, not null

     * @throws DateTimeException if unable to obtain the value for this field

     */

    public default int compare(TemporalAccessor temporal1, TemporalAccessor temporal2) {

         return Long.compare(temporal1.getLong(this), temporal2.getLong(this));

    }

    /**

     * Gets the range of valid values for the field.

     * <p>

     * All fields can be expressed as a {@code long} integer.

     * This method returns an object that describes the valid range for that value.

     * This method is generally only applicable to the ISO-8601 calendar system.

     * <p>

     * Note that the result only describes the minimum and maximum valid values

     * and it is important not to read too much into them. For example, there

     * could be values within the range that are invalid for the field.

     *

     * @return the range of valid values for the field, not null

     */

    ValueRange range();

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

    /**

     * Checks if this field is supported by the temporal object.

     * <p>

     * This determines whether the temporal accessor supports this field.

     * If this returns false, the the temporal cannot be queried for this field.

     * <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#isSupported(TemporalField)}:

     * <pre>

     *   // these two lines are equivalent, but the second approach is recommended

     *   temporal = thisField.doIsSupported(temporal);

     *   temporal = temporal.isSupported(thisField);

     * </pre>

     * It is recommended to use the second approach, {@code isSupported(TemporalField)},

     * as it is a lot clearer to read in code.

     * <p>

     * Implementations should determine whether they are supported using the fields

     * available in {@link ChronoField}.

     *

     * @param temporal  the temporal object to query, not null

     * @return true if the date-time can be queried for this field, false if not

     */

    boolean doIsSupported(TemporalAccessor temporal);

    /**

     * Get the range of valid values for this field using the temporal object to

     * refine the result.

     * <p>

     * This uses the temporal object to find the range of valid values for the field.

     * This is similar to {@link #range()}, however this method refines the result

     * using the temporal. For example, if the field is {@code DAY_OF_MONTH} the

     * {@code range} method is not accurate as there are four possible month lengths,

     * 28, 29, 30 and 31 days. Using this method with a date allows the range to be

     * accurate, returning just one of those four options.

     * <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#range(TemporalField)}:

     * <pre>

     *   // these two lines are equivalent, but the second approach is recommended

     *   temporal = thisField.doRange(temporal);

     *   temporal = temporal.range(thisField);

     * </pre>

     * It is recommended to use the second approach, {@code range(TemporalField)},

     * as it is a lot clearer to read in code.

     * <p>

     * Implementations should perform any queries or calculations using the fields

     * available in {@link ChronoField}.

     * If the field is not supported a {@code DateTimeException} must be thrown.

     *

     * @param temporal  the temporal object used to refine the result, not null

     * @return the range of valid values for this field, not null

     * @throws DateTimeException if the range for the field cannot be obtained

     */

    ValueRange doRange(TemporalAccessor temporal);

    /**

     * Gets the value of this field from the specified temporal object.

     * <p>

     * This queries the temporal object for the value of this field.

     * <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#getLong(TemporalField)}

     * (or {@link TemporalAccessor#get(TemporalField)}):

     * <pre>

     *   // these two lines are equivalent, but the second approach is recommended

     *   temporal = thisField.doGet(temporal);

     *   temporal = temporal.getLong(thisField);

     * </pre>

     * It is recommended to use the second approach, {@code getLong(TemporalField)},

     * as it is a lot clearer to read in code.

     * <p>

     * Implementations should perform any queries or calculations using the fields

     * available in {@link ChronoField}.

     * If the field is not supported a {@code DateTimeException} must be thrown.

     *

     * @param temporal  the temporal object to query, not null

     * @return the value of this field, not null

     * @throws DateTimeException if a value for the field cannot be obtained

     */

    long doGet(TemporalAccessor temporal);

    /**

     * Returns a copy of the specified temporal object with the value of this field set.

     * <p>

     * This returns a new temporal object based on the specified one with the value for

     * this field changed. For example, on a {@code LocalDate}, this could be used to

     * set the year, month or day-of-month.

     * The returned object has the same observable type as the specified object.

     * <p>

     * In some cases, changing a field is not fully defined. For example, if the target object is

     * a date representing the 31st January, then changing the month to February would be unclear.

     * In cases like this, the implementation is responsible for resolving the result.

     * Typically it will choose the previous valid date, which would be the last valid

     * day of February in this example.

     * <p>

     * There are two equivalent ways of using this method.

     * The first is to invoke this method directly.

     * The second is to use {@link Temporal#with(TemporalField, long)}:

     * <pre>

     *   // these two lines are equivalent, but the second approach is recommended

     *   temporal = thisField.doWith(temporal);

     *   temporal = temporal.with(thisField);

     * </pre>

     * It is recommended to use the second approach, {@code with(TemporalField)},

     * as it is a lot clearer to read in code.

     * <p>

     * Implementations should perform any queries or calculations using the fields

     * available in {@link ChronoField}.

     * If the field is not supported a {@code DateTimeException} must be thrown.

     * <p>

     * Implementations must not alter the specified temporal object.

     * Instead, an adjusted copy of the original must be returned.

     * This provides equivalent, safe behavior for immutable and mutable implementations.

     *

     * @param <R>  the type of the Temporal object

     * @param temporal the temporal object to adjust, not null

     * @param newValue the new value of the field

     * @return the adjusted temporal object, not null

     * @throws DateTimeException if the field cannot be set

     */

    <R extends Temporal> R doWith(R temporal, long newValue);

    /**

     * Resolves the date/time information in the builder

     * <p>

     * This method is invoked during the resolve of the builder.

     * Implementations should combine the associated field with others to form

     * objects like {@code LocalDate}, {@code LocalTime} and {@code LocalDateTime}

     *

     * @param builder  the builder to resolve, not null

     * @param value  the value of the associated field

     * @return true if builder has been changed, false otherwise

     * @throws DateTimeException if unable to resolve

     */

    boolean resolve(DateTimeBuilder builder, long value);

}