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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * This code is free software; you can redistribute it and/or modify it

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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) 2008-2012, 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.

 *

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 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT

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 */

package java.time;

import static java.time.temporal.ChronoField.MONTH_OF_YEAR;

import static java.time.temporal.ChronoUnit.DAYS;

import static java.time.temporal.ChronoUnit.MONTHS;

import static java.time.temporal.ChronoUnit.YEARS;

import java.io.DataInput;

import java.io.DataOutput;

import java.io.IOException;

import java.io.InvalidObjectException;

import java.io.ObjectStreamException;

import java.io.Serializable;

import java.time.chrono.ChronoLocalDate;

import java.time.chrono.Chronology;

import java.time.format.DateTimeParseException;

import java.time.temporal.ChronoUnit;

import java.time.temporal.Temporal;

import java.time.temporal.TemporalAmount;

import java.time.temporal.TemporalUnit;

import java.time.temporal.UnsupportedTemporalTypeException;

import java.time.temporal.ValueRange;

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

import java.util.Objects;

import java.util.regex.Matcher;

import java.util.regex.Pattern;

/**

 * A date-based amount of time, such as '2 years, 3 months and 4 days'.

 * <p>

 * This class models a quantity or amount of time in terms of years, months and days.

 * See {@link Duration} for the time-based equivalent to this class.

 * <p>

 * Durations and period differ in their treatment of daylight savings time

 * when added to {@link ZonedDateTime}. A {@code Duration} will add an exact

 * number of seconds, thus a duration of one day is always exactly 24 hours.

 * By contrast, a {@code Period} will add a conceptual day, trying to maintain

 * the local time.

 * <p>

 * For example, consider adding a period of one day and a duration of one day to

 * 18:00 on the evening before a daylight savings gap. The {@code Period} will add

 * the conceptual day and result in a {@code ZonedDateTime} at 18:00 the following day.

 * By contrast, the {@code Duration} will add exactly 24 hours, resulting in a

 * {@code ZonedDateTime} at 19:00 the following day (assuming a one hour DST gap).

 * <p>

 * The supported units of a period are {@link ChronoUnit#YEARS YEARS},

 * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}.

 * All three fields are always present, but may be set to zero.

 * <p>

 * The period may be used with any calendar system.

 * The meaning of a "year" or "month" is only applied when the object is added to a date.

 * <p>

 * The period is modeled as a directed amount of time, meaning that individual parts of the

 * period may be negative.

 * <p>

 * The months and years fields may be {@linkplain #normalized() normalized}.

 * The normalization assumes a 12 month year, so is not appropriate for all calendar systems.

 *

 * This class is immutable and thread-safe.

 *

 * @since 1.8

 */

public final class Period

        implements TemporalAmount, Serializable {

    /**

     * A constant for a period of zero.

     */

    public static final Period ZERO = new Period(0, 0, 0);

    /**

     * Serialization version.

     */

    private static final long serialVersionUID = -3587258372562876L;

    /**

     * The pattern for parsing.

     */

    private final static Pattern PATTERN =

            Pattern.compile("([-+]?)P(?:([-+]?[0-9]+)Y)?(?:([-+]?[0-9]+)M)?(?:([-+]?[0-9]+)D)?", Pattern.CASE_INSENSITIVE);

    /**

     * The set of supported units.

     */

    private final static List<TemporalUnit> SUPPORTED_UNITS =

            Collections.unmodifiableList(Arrays.<TemporalUnit>asList(YEARS, MONTHS, DAYS));

    /**

     * The number of years.

     */

    private final int years;

    /**

     * The number of months.

     */

    private final int months;

    /**

     * The number of days.

     */

    private final int days;

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

    /**

     * Obtains a {@code Period} representing a number of years.

     * <p>

     * The resulting period will have the specified years.

     * The months and days units will be zero.

     *

     * @param years  the number of years, positive or negative

     * @return the period of years, not null

     */

    public static Period ofYears(int years) {

        return create(years, 0, 0);

    }

    /**

     * Obtains a {@code Period} representing a number of months.

     * <p>

     * The resulting period will have the specified months.

     * The years and days units will be zero.

     *

     * @param months  the number of months, positive or negative

     * @return the period of months, not null

     */

    public static Period ofMonths(int months) {

        return create(0, months, 0);

    }

    /**

     * Obtains a {@code Period} representing a number of days.

     * <p>

     * The resulting period will have the specified days.

     * The years and months units will be zero.

     *

     * @param days  the number of days, positive or negative

     * @return the period of days, not null

     */

    public static Period ofDays(int days) {

        return create(0, 0, days);

    }

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

    /**

     * Obtains a {@code Period} representing a number of years, months and days.

     * <p>

     * This creates an instance based on years, months and days.

     *

     * @param years  the amount of years, may be negative

     * @param months  the amount of months, may be negative

     * @param days  the amount of days, may be negative

     * @return the period of years, months and days, not null

     */

    public static Period of(int years, int months, int days) {

        return create(years, months, days);

    }

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

    /**

     * Obtains an instance of {@code Period} from a temporal amount.

     * <p>

     * This obtains a period based on the specified amount.

     * A {@code TemporalAmount} represents an  amount of time, which may be

     * date-based or time-based, which this factory extracts to a period.

     * <p>

     * The conversion loops around the set of units from the amount and uses

     * the {@link ChronoUnit#YEARS YEARS}, {@link ChronoUnit#MONTHS MONTHS}

     * and {@link ChronoUnit#DAYS DAYS} units to create a period.

     * If any other units are found then an exception is thrown.

     *

     * @param amount  the temporal amount to convert, not null

     * @return the equivalent period, not null

     * @throws DateTimeException if unable to convert to a {@code Period}

     * @throws ArithmeticException if the amount of years, months or days exceeds an int

     */

    public static Period from(TemporalAmount amount) {

        Objects.requireNonNull(amount, "amount");

        int years = 0;

        int months = 0;

        int days = 0;

        for (TemporalUnit unit : amount.getUnits()) {

            long unitAmount = amount.get(unit);

            if (unit == ChronoUnit.YEARS) {

                years = Math.toIntExact(unitAmount);

            } else if (unit == ChronoUnit.MONTHS) {

                months = Math.toIntExact(unitAmount);

            } else if (unit == ChronoUnit.DAYS) {

                days = Math.toIntExact(unitAmount);

            } else {

                throw new DateTimeException("Unit must be Years, Months or Days, but was " + unit);

            }

        }

        return create(years, months, days);

    }

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

    /**

     * Obtains a {@code Period} from a text string such as {@code PnYnMnD}.

     * <p>

     * This will parse the string produced by {@code toString()} which is

     * based on the ISO-8601 period format {@code PnYnMnD}.

     * <p>

     * The string starts with an optional sign, denoted by the ASCII negative

     * or positive symbol. If negative, the whole period is negated.

     * The ASCII letter "P" is next in upper or lower case.

     * There are then three sections, each consisting of a number and a suffix.

     * At least one of the three sections must be present.

     * The sections have suffixes in ASCII of "Y", "M" and "D" for

     * years, months and days, accepted in upper or lower case.

     * The suffixes must occur in order.

     * The number part of each section must consist of ASCII digits.

     * The number may be prefixed by the ASCII negative or positive symbol.

     * The number must parse to an {@code int}.

     * <p>

     * The leading plus/minus sign, and negative values for other units are

     * not part of the ISO-8601 standard.

     *

     * @param text  the text to parse, not null

     * @return the parsed period, not null

     * @throws DateTimeParseException if the text cannot be parsed to a period

     */

    public static Period parse(CharSequence text) {

        Objects.requireNonNull(text, "text");

        Matcher matcher = PATTERN.matcher(text);

        if (matcher.matches()) {

            int negate = ("-".equals(matcher.group(1)) ? -1 : 1);

            String yearMatch = matcher.group(2);

            String monthMatch = matcher.group(3);

            String dayMatch = matcher.group(4);

            if (yearMatch != null || monthMatch != null || dayMatch != null) {

                try {

                    return create(parseNumber(text, yearMatch, negate),

                            parseNumber(text, monthMatch, negate),

                            parseNumber(text, dayMatch, negate));

                } catch (NumberFormatException ex) {

                    throw (DateTimeParseException) new DateTimeParseException("Text cannot be parsed to a Period", text, 0).initCause(ex);

                }

            }

        }

        throw new DateTimeParseException("Text cannot be parsed to a Period", text, 0);

    }

    private static int parseNumber(CharSequence text, String str, int negate) {

        if (str == null) {

            return 0;

        }

        int val = Integer.parseInt(str);

        try {

            return Math.multiplyExact(val, negate);

        } catch (ArithmeticException ex) {

            throw (DateTimeParseException) new DateTimeParseException("Text cannot be parsed to a Period", text, 0).initCause(ex);

        }

    }

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

    /**

     * Obtains a {@code Period} consisting of the number of years, months,

     * and days between two dates.

     * <p>

     * The start date is included, but the end date is not.

     * The period is calculated by removing complete months, then calculating

     * the remaining number of days, adjusting to ensure that both have the same sign.

     * The number of months is then split into years and months based on a 12 month year.

     * A month is considered if the end day-of-month is greater than or equal to the start day-of-month.

     * For example, from {@code 2010-01-15} to {@code 2011-03-18} is one year, two months and three days.

     * <p>

     * The result of this method can be a negative period if the end is before the start.

     * The negative sign will be the same in each of year, month and day.

     *

     * @param startDate  the start date, inclusive, not null

     * @param endDate  the end date, exclusive, not null

     * @return the period between this date and the end date, not null

     * @see ChronoLocalDate#periodUntil(ChronoLocalDate)

     */

    public static Period between(LocalDate startDate, LocalDate endDate) {

        return startDate.periodUntil(endDate);

    }

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

    /**

     * Creates an instance.

     *

     * @param years  the amount

     * @param months  the amount

     * @param days  the amount

     */

    private static Period create(int years, int months, int days) {

        if ((years | months | days) == 0) {

            return ZERO;

        }

        return new Period(years, months, days);

    }

    /**

     * Constructor.

     *

     * @param years  the amount

     * @param months  the amount

     * @param days  the amount

     */

    private Period(int years, int months, int days) {

        this.years = years;

        this.months = months;

        this.days = days;

    }

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

    /**

     * Gets the value of the requested unit.

     * <p>

     * This returns a value for each of the three supported units,

     * {@link ChronoUnit#YEARS YEARS}, {@link ChronoUnit#MONTHS MONTHS} and

     * {@link ChronoUnit#DAYS DAYS}.

     * All other units throw an exception.

     *

     * @param unit the {@code TemporalUnit} for which to return the value

     * @return the long value of the unit

     * @throws DateTimeException if the unit is not supported

     * @throws UnsupportedTemporalTypeException if the unit is not supported

     */

    @Override

    public long get(TemporalUnit unit) {

        if (unit == ChronoUnit.YEARS) {

            return getYears();

        } else if (unit == ChronoUnit.MONTHS) {

            return getMonths();

        } else if (unit == ChronoUnit.DAYS) {

            return getDays();

        } else {

            throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit.getName());

        }

    }

    /**

     * Gets the set of units supported by this period.

     * <p>

     * The supported units are {@link ChronoUnit#YEARS YEARS},

     * {@link ChronoUnit#MONTHS MONTHS} and {@link ChronoUnit#DAYS DAYS}.

     * They are returned in the order years, months, days.

     * <p>

     * This set can be used in conjunction with {@link #get(TemporalUnit)}

     * to access the entire state of the period.

     *

     * @return a list containing the years, months and days units, not null

     */

    @Override

    public List<TemporalUnit> getUnits() {

        return SUPPORTED_UNITS;

    }

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

    /**

     * Checks if all three units of this period are zero.

     * <p>

     * A zero period has the value zero for the years, months and days units.

     *

     * @return true if this period is zero-length

     */

    public boolean isZero() {

        return (this == ZERO);

    }

    /**

     * Checks if any of the three units of this period are negative.

     * <p>

     * This checks whether the years, months or days units are less than zero.

     *

     * @return true if any unit of this period is negative

     */

    public boolean isNegative() {

        return years < 0 || months < 0 || days < 0;

    }

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

    /**

     * Gets the amount of years of this period.

     * <p>

     * This returns the years unit.

     * <p>

     * The months unit is not normalized with the years unit.

     * This means that a period of "15 months" is different to a period

     * of "1 year and 3 months".

     *

     * @return the amount of years of this period, may be negative

     */

    public int getYears() {

        return years;

    }

    /**

     * Gets the amount of months of this period.

     * <p>

     * This returns the months unit.

     * <p>

     * The months unit is not normalized with the years unit.

     * This means that a period of "15 months" is different to a period

     * of "1 year and 3 months".

     *

     * @return the amount of months of this period, may be negative

     */

    public int getMonths() {

        return months;

    }

    /**

     * Gets the amount of days of this period.

     * <p>

     * This returns the days unit.

     *

     * @return the amount of days of this period, may be negative

     */

    public int getDays() {

        return days;

    }

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

    /**

     * Returns a copy of this period with the specified amount of years.

     * <p>

     * This sets the amount of the years unit in a copy of this period.

     * The months and days units are unaffected.

     * <p>

     * The months unit is not normalized with the years unit.

     * This means that a period of "15 months" is different to a period

     * of "1 year and 3 months".

     * <p>

     * This instance is immutable and unaffected by this method call.

     *

     * @param years  the years to represent, may be negative

     * @return a {@code Period} based on this period with the requested years, not null

     */

    public Period withYears(int years) {

        if (years == this.years) {

            return this;

        }

        return create(years, months, days);

    }

    /**

     * Returns a copy of this period with the specified amount of months.

     * <p>

     * This sets the amount of the months unit in a copy of this period.

     * The years and days units are unaffected.

     * <p>