/*
 * Copyright (c) 2012, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation. Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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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) 2007-2012, 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package java.time;

import static java.time.LocalTime.MINUTES_PER_HOUR;
import static java.time.LocalTime.NANOS_PER_MILLI;
import static java.time.LocalTime.NANOS_PER_SECOND;
import static java.time.LocalTime.SECONDS_PER_DAY;
import static java.time.LocalTime.SECONDS_PER_HOUR;
import static java.time.LocalTime.SECONDS_PER_MINUTE;
import static java.time.temporal.ChronoField.NANO_OF_SECOND;
import static java.time.temporal.ChronoUnit.DAYS;
import static java.time.temporal.ChronoUnit.NANOS;
import static java.time.temporal.ChronoUnit.SECONDS;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.RoundingMode;
import java.time.format.DateTimeParseException;
import java.time.temporal.ChronoField;
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.util.List;
import java.util.Objects;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * A time-based amount of time, such as '34.5 seconds'.
 * <p>
 * This class models a quantity or amount of time in terms of seconds and nanoseconds.
 * It can be accessed using other duration-based units, such as minutes and hours.
 * In addition, the {@link ChronoUnit#DAYS DAYS} unit can be used and is treated as
 * exactly equal to 24 hours, thus ignoring daylight savings effects.
 * See {@link Period} for the date-based equivalent to this class.
 * <p>
 * A physical duration could be of infinite length.
 * For practicality, the duration is stored with constraints similar to {@link Instant}.
 * The duration uses nanosecond resolution with a maximum value of the seconds that can
 * be held in a {@code long}. This is greater than the current estimated age of the universe.
 * <p>
 * The range of a duration requires the storage of a number larger than a {@code long}.
 * To achieve this, the class stores a {@code long} representing seconds and an {@code int}
 * representing nanosecond-of-second, which will always be between 0 and 999,999,999.
 * The model is of a directed duration, meaning that the duration may be negative.
 * <p>
 * The duration is measured in "seconds", but these are not necessarily identical to
 * the scientific "SI second" definition based on atomic clocks.
 * This difference only impacts durations measured near a leap-second and should not affect
 * most applications.
 * See {@link Instant} for a discussion as to the meaning of the second and time-scales.
 *
 * <p>
 * This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
 * class; use of identity-sensitive operations (including reference equality
 * ({@code ==}), identity hash code, or synchronization) on instances of
 * {@code Duration} may have unpredictable results and should be avoided.
 * The {@code equals} method should be used for comparisons.
 *
 * @implSpec
 * This class is immutable and thread-safe.
 *
 * @since 1.8
 */
public final class Duration
 implements TemporalAmount, Comparable<Duration>, Serializable {

 /**
 * Constant for a duration of zero.
 */
 public static final Duration ZERO = new Duration(0, 0);
 /**
 * Serialization version.
 */
 private static final long serialVersionUID = 3078945930695997490L;
 /**
 * Constant for nanos per second.
 */
 private static final BigInteger BI_NANOS_PER_SECOND = BigInteger.valueOf(NANOS_PER_SECOND);
 /**
 * The pattern for parsing.
 */
 private static class Lazy {
 static final Pattern PATTERN =
 Pattern.compile("([-+]?)P(?:([-+]?[0-9]+)D)?" +
 "(T(?:([-+]?[0-9]+)H)?(?:([-+]?[0-9]+)M)?(?:([-+]?[0-9]+)(?:[.,]([0-9]{0,9}))?S)?)?",
 Pattern.CASE_INSENSITIVE);
 }

 /**
 * The number of seconds in the duration.
 */
 private final long seconds;
 /**
 * The number of nanoseconds in the duration, expressed as a fraction of the
 * number of seconds. This is always positive, and never exceeds 999,999,999.
 */
 private final int nanos;

 //-----------------------------------------------------------------------
 /**
 * Obtains a {@code Duration} representing a number of standard 24 hour days.
 * <p>
 * The seconds are calculated based on the standard definition of a day,
 * where each day is 86400 seconds which implies a 24 hour day.
 * The nanosecond in second field is set to zero.
 *
 * @param days the number of days, positive or negative
 * @return a {@code Duration}, not null
 * @throws ArithmeticException if the input days exceeds the capacity of {@code Duration}
 */
 public static Duration ofDays(long days) {
 return create(Math.multiplyExact(days, SECONDS_PER_DAY), 0);
 }

 /**
 * Obtains a {@code Duration} representing a number of standard hours.
 * <p>
 * The seconds are calculated based on the standard definition of an hour,
 * where each hour is 3600 seconds.
 * The nanosecond in second field is set to zero.
 *
 * @param hours the number of hours, positive or negative
 * @return a {@code Duration}, not null
 * @throws ArithmeticException if the input hours exceeds the capacity of {@code Duration}
 */
 public static Duration ofHours(long hours) {
 return create(Math.multiplyExact(hours, SECONDS_PER_HOUR), 0);
 }

 /**
 * Obtains a {@code Duration} representing a number of standard minutes.
 * <p>
 * The seconds are calculated based on the standard definition of a minute,
 * where each minute is 60 seconds.
 * The nanosecond in second field is set to zero.
 *
 * @param minutes the number of minutes, positive or negative
 * @return a {@code Duration}, not null
 * @throws ArithmeticException if the input minutes exceeds the capacity of {@code Duration}
 */
 public static Duration ofMinutes(long minutes) {
 return create(Math.multiplyExact(minutes, SECONDS_PER_MINUTE), 0);
 }

 //-----------------------------------------------------------------------
 /**
 * Obtains a {@code Duration} representing a number of seconds.
 * <p>
 * The nanosecond in second field is set to zero.
 *
 * @param seconds the number of seconds, positive or negative
 * @return a {@code Duration}, not null
 */
 public static Duration ofSeconds(long seconds) {
 return create(seconds, 0);
 }

 /**
 * Obtains a {@code Duration} representing a number of seconds and an
 * adjustment in nanoseconds.
 * <p>
 * This method allows an arbitrary number of nanoseconds to be passed in.
 * The factory will alter the values of the second and nanosecond in order
 * to ensure that the stored nanosecond is in the range 0 to 999,999,999.
 * For example, the following will result in exactly the same duration:
 * <pre>
 * Duration.ofSeconds(3, 1);
 * Duration.ofSeconds(4, -999_999_999);
 * Duration.ofSeconds(2, 1000_000_001);
 * </pre>
 *
 * @param seconds the number of seconds, positive or negative
 * @param nanoAdjustment the nanosecond adjustment to the number of seconds, positive or negative
 * @return a {@code Duration}, not null
 * @throws ArithmeticException if the adjustment causes the seconds to exceed the capacity of {@code Duration}
 */
 public static Duration ofSeconds(long seconds, long nanoAdjustment) {
 long secs = Math.addExact(seconds, Math.floorDiv(nanoAdjustment, NANOS_PER_SECOND));
 int nos = (int) Math.floorMod(nanoAdjustment, NANOS_PER_SECOND);
 return create(secs, nos);
 }

 //-----------------------------------------------------------------------
 /**
 * Obtains a {@code Duration} representing a number of milliseconds.
 * <p>
 * The seconds and nanoseconds are extracted from the specified milliseconds.
 *
 * @param millis the number of milliseconds, positive or negative
 * @return a {@code Duration}, not null
 */
 public static Duration ofMillis(long millis) {
 long secs = millis / 1000;
 int mos = (int) (millis % 1000);
 if (mos < 0) {
 mos += 1000;
 secs--;
 }
 return create(secs, mos * 1000_000);
 }

 //-----------------------------------------------------------------------
 /**
 * Obtains a {@code Duration} representing a number of nanoseconds.
 * <p>
 * The seconds and nanoseconds are extracted from the specified nanoseconds.
 *
 * @param nanos the number of nanoseconds, positive or negative
 * @return a {@code Duration}, not null
 */
 public static Duration ofNanos(long nanos) {
 long secs = nanos / NANOS_PER_SECOND;
 int nos = (int) (nanos % NANOS_PER_SECOND);
 if (nos < 0) {
 nos += NANOS_PER_SECOND;
 secs--;
 }
 return create(secs, nos);
 }

 //-----------------------------------------------------------------------
 /**
 * Obtains a {@code Duration} representing an amount in the specified unit.
 * <p>
 * The parameters represent the two parts of a phrase like '6 Hours'. For example:
 * <pre>
 * Duration.of(3, SECONDS);
 * Duration.of(465, HOURS);
 * </pre>
 * Only a subset of units are accepted by this method.
 * The unit must either have an {@linkplain TemporalUnit#isDurationEstimated() exact duration} or
 * be {@link ChronoUnit#DAYS} which is treated as 24 hours. Other units throw an exception.
 *
 * @param amount the amount of the duration, measured in terms of the unit, positive or negative
 * @param unit the unit that the duration is measured in, must have an exact duration, not null
 * @return a {@code Duration}, not null
 * @throws DateTimeException if the period unit has an estimated duration
 * @throws ArithmeticException if a numeric overflow occurs
 */
 public static Duration of(long amount, TemporalUnit unit) {
 return ZERO.plus(amount, unit);
 }

 //-----------------------------------------------------------------------
 /**
 * Obtains an instance of {@code Duration} from a temporal amount.
 * <p>
 * This obtains a duration 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 duration.
 * <p>
 * The conversion loops around the set of units from the amount and uses
 * the {@linkplain TemporalUnit#getDuration() duration} of the unit to
 * calculate the total {@code Duration}.
 * Only a subset of units are accepted by this method. The unit must either
 * have an {@linkplain TemporalUnit#isDurationEstimated() exact duration}
 * or be {@link ChronoUnit#DAYS} which is treated as 24 hours.
 * If any other units are found then an exception is thrown.
 *
 * @param amount the temporal amount to convert, not null
 * @return the equivalent duration, not null
 * @throws DateTimeException if unable to convert to a {@code Duration}
 * @throws ArithmeticException if numeric overflow occurs
 */
 public static Duration from(TemporalAmount amount) {
 Objects.requireNonNull(amount, "amount");
 Duration duration = ZERO;
 for (TemporalUnit unit : amount.getUnits()) {
 duration = duration.plus(amount.get(unit), unit);
 }
 return duration;
 }

 //-----------------------------------------------------------------------
 /**
 * Obtains a {@code Duration} from a text string such as {@code PnDTnHnMn.nS}.
 * <p>
 * This will parse a textual representation of a duration, including the
 * string produced by {@code toString()}. The formats accepted are based
 * on the ISO-8601 duration format {@code PnDTnHnMn.nS} with days
 * considered to be exactly 24 hours.
 * <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 four sections, each consisting of a number and a suffix.
 * The sections have suffixes in ASCII of "D", "H", "M" and "S" for
 * days, hours, minutes and seconds, accepted in upper or lower case.
 * The suffixes must occur in order. The ASCII letter "T" must occur before
 * the first occurrence, if any, of an hour, minute or second section.
 * At least one of the four sections must be present, and if "T" is present
 * there must be at least one section after the "T".
 * The number part of each section must consist of one or more ASCII digits.
 * The number may be prefixed by the ASCII negative or positive symbol.
 * The number of days, hours and minutes must parse to a {@code long}.
 * The number of seconds must parse to a {@code long} with optional fraction.
 * The decimal point may be either a dot or a comma.
 * The fractional part may have from zero to 9 digits.
 * <p>
 * The leading plus/minus sign, and negative values for other units are
 * not part of the ISO-8601 standard.
 * <p>
 * Examples:
 * <pre>
 * "PT20.345S" -- parses as "20.345 seconds"
 * "PT15M" -- parses as "15 minutes" (where a minute is 60 seconds)
 * "PT10H" -- parses as "10 hours" (where an hour is 3600 seconds)
 * "P2D" -- parses as "2 days" (where a day is 24 hours or 86400 seconds)
 * "P2DT3H4M" -- parses as "2 days, 3 hours and 4 minutes"
 * "PT-6H3M" -- parses as "-6 hours and +3 minutes"
 * "-PT6H3M" -- parses as "-6 hours and -3 minutes"
 * "-PT-6H+3M" -- parses as "+6 hours and -3 minutes"
 * </pre>
 *
 * @param text the text to parse, not null
 * @return the parsed duration, not null
 * @throws DateTimeParseException if the text cannot be parsed to a duration
 */
 public static Duration parse(CharSequence text) {
 Objects.requireNonNull(text, "text");
 Matcher matcher = Lazy.PATTERN.matcher(text);
 if (matcher.matches()) {
 // check for letter T but no time sections
 if (!charMatch(text, matcher.start(3), matcher.end(3), 'T')) {
 boolean negate = charMatch(text, matcher.start(1), matcher.end(1), '-');

 int dayStart = matcher.start(2), dayEnd = matcher.end(2);
 int hourStart = matcher.start(4), hourEnd = matcher.end(4);
 int minuteStart = matcher.start(5), minuteEnd = matcher.end(5);
 int secondStart = matcher.start(6), secondEnd = matcher.end(6);
 int fractionStart = matcher.start(7), fractionEnd = matcher.end(7);

 if (dayStart >= 0 || hourStart >= 0 || minuteStart >= 0 || secondStart >= 0) {
 long daysAsSecs = parseNumber(text, dayStart, dayEnd, SECONDS_PER_DAY, "days");
 long hoursAsSecs = parseNumber(text, hourStart, hourEnd, SECONDS_PER_HOUR, "hours");
 long minsAsSecs = parseNumber(text, minuteStart, minuteEnd, SECONDS_PER_MINUTE, "minutes");
 long seconds = parseNumber(text, secondStart, secondEnd, 1, "seconds");
 boolean negativeSecs = secondStart >= 0 && text.charAt(secondStart) == '-';
 int nanos = parseFraction(text, fractionStart, fractionEnd, negativeSecs ? -1 : 1);
 try {
 return create(negate, daysAsSecs, hoursAsSecs, minsAsSecs, seconds, nanos);
 } catch (ArithmeticException ex) {
 throw (DateTimeParseException) new DateTimeParseException("Text cannot be parsed to a Duration: overflow", text, 0).initCause(ex);
 }
 }
 }
 }
 throw new DateTimeParseException("Text cannot be parsed to a Duration", text, 0);
 }

 private static boolean charMatch(CharSequence text, int start, int end, char c) {
 return (start >= 0 && end == start + 1 && text.charAt(start) == c);
 }

 private static long parseNumber(CharSequence text, int start, int end, int multiplier, String errorText) {
 // regex limits to [-+]?[0-9]+
 if (start < 0 || end < 0) {
 return 0;
 }
 try {
 long val = Long.parseLong(text, start, end, 10);
 return Math.multiplyExact(val, multiplier);
 } catch (NumberFormatException | ArithmeticException ex) {
 throw (DateTimeParseException) new DateTimeParseException("Text cannot be parsed to a Duration: " + errorText, text, 0).initCause(ex);
 }
 }

 private static int parseFraction(CharSequence text, int start, int end, int negate) {
 // regex limits to [0-9]{0,9}
 if (start < 0 || end < 0 || end - start == 0) {
 return 0;
 }
 try {
 int fraction = Integer.parseInt(text, start, end, 10);

 // for number strings smaller than 9 digits, interpret as if there
 // were trailing zeros
 for (int i = end - start; i < 9; i++) {
 fraction *= 10;
 }
 return fraction * negate;
 } catch (NumberFormatException | ArithmeticException ex) {
 throw (DateTimeParseException) new DateTimeParseException("Text cannot be parsed to a Duration: fraction", text, 0).initCause(ex);
 }
 }

 private static Duration create(boolean negate, long daysAsSecs, long hoursAsSecs, long minsAsSecs, long secs, int nanos) {
 long seconds = Math.addExact(daysAsSecs, Math.addExact(hoursAsSecs, Math.addExact(minsAsSecs, secs)));
 if (negate) {
 return ofSeconds(seconds, nanos).negated();
 }
 return ofSeconds(seconds, nanos);
 }

 //-----------------------------------------------------------------------
 /**
 * Obtains a {@code Duration} representing the duration between two temporal objects.
 * <p>
 * This calculates the duration between two temporal objects. If the objects
 * are of different types, then the duration is calculated based on the type
 * of the first object. For example, if the first argument is a {@code LocalTime}
 * then the second argument is converted to a {@code LocalTime}.
 * <p>
 * The specified temporal objects must support the {@link ChronoUnit#SECONDS SECONDS} unit.
 * For full accuracy, either the {@link ChronoUnit#NANOS NANOS} unit or the
 * {@link ChronoField#NANO_OF_SECOND NANO_OF_SECOND} field should be supported.
 * <p>
 * The result of this method can be a negative period if the end is before the start.
 * To guarantee to obtain a positive duration call {@link #abs()} on the result.
 *
 * @param startInclusive the start instant, inclusive, not null
 * @param endExclusive the end instant, exclusive, not null
 * @return a {@code Duration}, not null
 * @throws DateTimeException if the seconds between the temporals cannot be obtained
 * @throws ArithmeticException if the calculation exceeds the capacity of {@code Duration}
 */
 public static Duration between(Temporal startInclusive, Temporal endExclusive) {
 try {
 return ofNanos(startInclusive.until(endExclusive, NANOS));
 } catch (DateTimeException | ArithmeticException ex) {
 long secs = startInclusive.until(endExclusive, SECONDS);
 long nanos;
 try {
 nanos = endExclusive.getLong(NANO_OF_SECOND) - startInclusive.getLong(NANO_OF_SECOND);
 if (secs > 0 && nanos < 0) {
 secs++;
 } else if (secs < 0 && nanos > 0) {
 secs--;
 }
 } catch (DateTimeException ex2) {
 nanos = 0;
 }
 return ofSeconds(secs, nanos);
 }
 }

 //-----------------------------------------------------------------------
 /**
 * Obtains an instance of {@code Duration} using seconds and nanoseconds.
 *
 * @param seconds the length of the duration in seconds, positive or negative
 * @param nanoAdjustment the nanosecond adjustment within the second, from 0 to 999,999,999
 */
 private static Duration create(long seconds, int nanoAdjustment) {
 if ((seconds | nanoAdjustment) == 0) {
 return ZERO;
 }
 return new Duration(seconds, nanoAdjustment);
 }

 /**
 * Constructs an instance of {@code Duration} using seconds and nanoseconds.
 *
 * @param seconds the length of the duration in seconds, positive or negative
 * @param nanos the nanoseconds within the second, from 0 to 999,999,999
 */
 private Duration(long seconds, int nanos) {
 super();
 this.seconds = seconds;
 this.nanos = nanos;
 }

 //-----------------------------------------------------------------------
 /**
 * Gets the value of the requested unit.
 * <p>
 * This returns a value for each of the two supported units,
 * {@link ChronoUnit#SECONDS SECONDS} and {@link ChronoUnit#NANOS NANOS}.
 * 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 == SECONDS) {
 return seconds;
 } else if (unit == NANOS) {
 return nanos;
 } else {
 throw new UnsupportedTemporalTypeException("Unsupported unit: " + unit);
 }
 }

 /**
 * Gets the set of units supported by this duration.
 * <p>
 * The supported units are {@link ChronoUnit#SECONDS SECONDS},
 * and {@link ChronoUnit#NANOS NANOS}.
 * They are returned in the order seconds, nanos.
 * <p>
 * This set can be used in conjunction with {@link #get(TemporalUnit)}
 * to access the entire state of the duration.
 *
 * @return a list containing the seconds and nanos units, not null
 */
 @Override
 public List<TemporalUnit> getUnits() {
 return DurationUnits.UNITS;
 }

 /**
 * Private class to delay initialization of this list until needed.
 * The circular dependency between Duration and ChronoUnit prevents
 * the simple initialization in Duration.
 */
 private static class DurationUnits {
 static final List<TemporalUnit> UNITS = List.of(SECONDS, NANOS);
 }

 //-----------------------------------------------------------------------
 /**
 * Checks if this duration is zero length.
 * <p>
 * A {@code Duration} represents a directed distance between two points on
 * the time-line and can therefore be positive, zero or negative.
 * This method checks whether the length is zero.
 *
 * @return true if this duration has a total length equal to zero
 */
 public boolean isZero() {
 return (seconds | nanos) == 0;
 }

 /**
 * Checks if this duration is negative, excluding zero.
 * <p>
 * A {@code Duration} represents a directed distance between two points on
 * the time-line and can therefore be positive, zero or negative.
 * This method checks whether the length is less than zero.
 *
 * @return true if this duration has a total length less than zero
 */
 public boolean isNegative() {
 return seconds < 0;
 }

 //-----------------------------------------------------------------------
 /**
 * Gets the number of seconds in this duration.
 * <p>
 * The length of the duration is stored using two fields - seconds and nanoseconds.
 * The nanoseconds part is a value from 0 to 999,999,999 that is an adjustment to
 * the length in seconds.
 * The total duration is defined by calling this method and {@link #getNano()}.
 * <p>
 * A {@code Duration} represents a directed distance between two points on the time-line.
 * A negative duration is expressed by the negative sign of the seconds part.
 * A duration of -1 nanosecond is stored as -1 seconds plus 999,999,999 nanoseconds.
 *
 * @return the whole seconds part of the length of the duration, positive or negative
 */
 public long getSeconds() {
 return seconds;
 }

 /**
 * Gets the number of nanoseconds within the second in this duration.
 * <p>
 * The length of the duration is stored using two fields - seconds and nanoseconds.
 * The nanoseconds part is a value from 0 to 999,999,999 that is an adjustment to
 * the length in seconds.
 * The total duration is defined by calling this method and {@link #getSeconds()}.
 * <p>
 * A {@code Duration} represents a directed distance between two points on the time-line.
 * A negative duration is expressed by the negative sign of the seconds part.
 * A duration of -1 nanosecond is stored as -1 seconds plus 999,999,999 nanoseconds.
 *
 * @return the nanoseconds within the second part of the length of the duration, from 0 to 999,999,999
 */
 public int getNano() {
 return nanos;
 }

 //-----------------------------------------------------------------------
 /**
 * Returns a copy of this duration with the specified amount of seconds.
 * <p>
 * This returns a duration with the specified seconds, retaining the
 * nano-of-second part of this duration.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param seconds the seconds to represent, may be negative
 * @return a {@code Duration} based on this period with the requested seconds, not null
 */
 public Duration withSeconds(long seconds) {
 return create(seconds, nanos);
 }

 /**
 * Returns a copy of this duration with the specified nano-of-second.
 * <p>
 * This returns a duration with the specified nano-of-second, retaining the
 * seconds part of this duration.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param nanoOfSecond the nano-of-second to represent, from 0 to 999,999,999
 * @return a {@code Duration} based on this period with the requested nano-of-second, not null
 * @throws DateTimeException if the nano-of-second is invalid
 */
 public Duration withNanos(int nanoOfSecond) {
 NANO_OF_SECOND.checkValidIntValue(nanoOfSecond);
 return create(seconds, nanoOfSecond);
 }

 //-----------------------------------------------------------------------
 /**
 * Returns a copy of this duration with the specified duration added.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param duration the duration to add, positive or negative, not null
 * @return a {@code Duration} based on this duration with the specified duration added, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration plus(Duration duration) {
 return plus(duration.getSeconds(), duration.getNano());
 }

 /**
 * Returns a copy of this duration with the specified duration added.
 * <p>
 * The duration amount is measured in terms of the specified unit.
 * Only a subset of units are accepted by this method.
 * The unit must either have an {@linkplain TemporalUnit#isDurationEstimated() exact duration} or
 * be {@link ChronoUnit#DAYS} which is treated as 24 hours. Other units throw an exception.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param amountToAdd the amount to add, measured in terms of the unit, positive or negative
 * @param unit the unit that the amount is measured in, must have an exact duration, not null
 * @return a {@code Duration} based on this duration with the specified duration added, not null
 * @throws UnsupportedTemporalTypeException if the unit is not supported
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration plus(long amountToAdd, TemporalUnit unit) {
 Objects.requireNonNull(unit, "unit");
 if (unit == DAYS) {
 return plus(Math.multiplyExact(amountToAdd, SECONDS_PER_DAY), 0);
 }
 if (unit.isDurationEstimated()) {
 throw new UnsupportedTemporalTypeException("Unit must not have an estimated duration");
 }
 if (amountToAdd == 0) {
 return this;
 }
 if (unit instanceof ChronoUnit) {
 switch ((ChronoUnit) unit) {
 case NANOS: return plusNanos(amountToAdd);
 case MICROS: return plusSeconds((amountToAdd / (1000_000L * 1000)) * 1000).plusNanos((amountToAdd % (1000_000L * 1000)) * 1000);
 case MILLIS: return plusMillis(amountToAdd);
 case SECONDS: return plusSeconds(amountToAdd);
 }
 return plusSeconds(Math.multiplyExact(unit.getDuration().seconds, amountToAdd));
 }
 Duration duration = unit.getDuration().multipliedBy(amountToAdd);
 return plusSeconds(duration.getSeconds()).plusNanos(duration.getNano());
 }

 //-----------------------------------------------------------------------
 /**
 * Returns a copy of this duration with the specified duration in standard 24 hour days added.
 * <p>
 * The number of days is multiplied by 86400 to obtain the number of seconds to add.
 * This is based on the standard definition of a day as 24 hours.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param daysToAdd the days to add, positive or negative
 * @return a {@code Duration} based on this duration with the specified days added, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration plusDays(long daysToAdd) {
 return plus(Math.multiplyExact(daysToAdd, SECONDS_PER_DAY), 0);
 }

 /**
 * Returns a copy of this duration with the specified duration in hours added.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param hoursToAdd the hours to add, positive or negative
 * @return a {@code Duration} based on this duration with the specified hours added, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration plusHours(long hoursToAdd) {
 return plus(Math.multiplyExact(hoursToAdd, SECONDS_PER_HOUR), 0);
 }

 /**
 * Returns a copy of this duration with the specified duration in minutes added.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param minutesToAdd the minutes to add, positive or negative
 * @return a {@code Duration} based on this duration with the specified minutes added, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration plusMinutes(long minutesToAdd) {
 return plus(Math.multiplyExact(minutesToAdd, SECONDS_PER_MINUTE), 0);
 }

 /**
 * Returns a copy of this duration with the specified duration in seconds added.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param secondsToAdd the seconds to add, positive or negative
 * @return a {@code Duration} based on this duration with the specified seconds added, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration plusSeconds(long secondsToAdd) {
 return plus(secondsToAdd, 0);
 }

 /**
 * Returns a copy of this duration with the specified duration in milliseconds added.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param millisToAdd the milliseconds to add, positive or negative
 * @return a {@code Duration} based on this duration with the specified milliseconds added, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration plusMillis(long millisToAdd) {
 return plus(millisToAdd / 1000, (millisToAdd % 1000) * 1000_000);
 }

 /**
 * Returns a copy of this duration with the specified duration in nanoseconds added.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param nanosToAdd the nanoseconds to add, positive or negative
 * @return a {@code Duration} based on this duration with the specified nanoseconds added, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration plusNanos(long nanosToAdd) {
 return plus(0, nanosToAdd);
 }

 /**
 * Returns a copy of this duration with the specified duration added.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param secondsToAdd the seconds to add, positive or negative
 * @param nanosToAdd the nanos to add, positive or negative
 * @return a {@code Duration} based on this duration with the specified seconds added, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 private Duration plus(long secondsToAdd, long nanosToAdd) {
 if ((secondsToAdd | nanosToAdd) == 0) {
 return this;
 }
 long epochSec = Math.addExact(seconds, secondsToAdd);
 epochSec = Math.addExact(epochSec, nanosToAdd / NANOS_PER_SECOND);
 nanosToAdd = nanosToAdd % NANOS_PER_SECOND;
 long nanoAdjustment = nanos + nanosToAdd; // safe int+NANOS_PER_SECOND
 return ofSeconds(epochSec, nanoAdjustment);
 }

 //-----------------------------------------------------------------------
 /**
 * Returns a copy of this duration with the specified duration subtracted.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param duration the duration to subtract, positive or negative, not null
 * @return a {@code Duration} based on this duration with the specified duration subtracted, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration minus(Duration duration) {
 long secsToSubtract = duration.getSeconds();
 int nanosToSubtract = duration.getNano();
 if (secsToSubtract == Long.MIN_VALUE) {
 return plus(Long.MAX_VALUE, -nanosToSubtract).plus(1, 0);
 }
 return plus(-secsToSubtract, -nanosToSubtract);
 }

 /**
 * Returns a copy of this duration with the specified duration subtracted.
 * <p>
 * The duration amount is measured in terms of the specified unit.
 * Only a subset of units are accepted by this method.
 * The unit must either have an {@linkplain TemporalUnit#isDurationEstimated() exact duration} or
 * be {@link ChronoUnit#DAYS} which is treated as 24 hours. Other units throw an exception.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param amountToSubtract the amount to subtract, measured in terms of the unit, positive or negative
 * @param unit the unit that the amount is measured in, must have an exact duration, not null
 * @return a {@code Duration} based on this duration with the specified duration subtracted, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration minus(long amountToSubtract, TemporalUnit unit) {
 return (amountToSubtract == Long.MIN_VALUE ? plus(Long.MAX_VALUE, unit).plus(1, unit) : plus(-amountToSubtract, unit));
 }

 //-----------------------------------------------------------------------
 /**
 * Returns a copy of this duration with the specified duration in standard 24 hour days subtracted.
 * <p>
 * The number of days is multiplied by 86400 to obtain the number of seconds to subtract.
 * This is based on the standard definition of a day as 24 hours.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param daysToSubtract the days to subtract, positive or negative
 * @return a {@code Duration} based on this duration with the specified days subtracted, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration minusDays(long daysToSubtract) {
 return (daysToSubtract == Long.MIN_VALUE ? plusDays(Long.MAX_VALUE).plusDays(1) : plusDays(-daysToSubtract));
 }

 /**
 * Returns a copy of this duration with the specified duration in hours subtracted.
 * <p>
 * The number of hours is multiplied by 3600 to obtain the number of seconds to subtract.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param hoursToSubtract the hours to subtract, positive or negative
 * @return a {@code Duration} based on this duration with the specified hours subtracted, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration minusHours(long hoursToSubtract) {
 return (hoursToSubtract == Long.MIN_VALUE ? plusHours(Long.MAX_VALUE).plusHours(1) : plusHours(-hoursToSubtract));
 }

 /**
 * Returns a copy of this duration with the specified duration in minutes subtracted.
 * <p>
 * The number of hours is multiplied by 60 to obtain the number of seconds to subtract.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param minutesToSubtract the minutes to subtract, positive or negative
 * @return a {@code Duration} based on this duration with the specified minutes subtracted, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration minusMinutes(long minutesToSubtract) {
 return (minutesToSubtract == Long.MIN_VALUE ? plusMinutes(Long.MAX_VALUE).plusMinutes(1) : plusMinutes(-minutesToSubtract));
 }

 /**
 * Returns a copy of this duration with the specified duration in seconds subtracted.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param secondsToSubtract the seconds to subtract, positive or negative
 * @return a {@code Duration} based on this duration with the specified seconds subtracted, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration minusSeconds(long secondsToSubtract) {
 return (secondsToSubtract == Long.MIN_VALUE ? plusSeconds(Long.MAX_VALUE).plusSeconds(1) : plusSeconds(-secondsToSubtract));
 }

 /**
 * Returns a copy of this duration with the specified duration in milliseconds subtracted.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param millisToSubtract the milliseconds to subtract, positive or negative
 * @return a {@code Duration} based on this duration with the specified milliseconds subtracted, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration minusMillis(long millisToSubtract) {
 return (millisToSubtract == Long.MIN_VALUE ? plusMillis(Long.MAX_VALUE).plusMillis(1) : plusMillis(-millisToSubtract));
 }

 /**
 * Returns a copy of this duration with the specified duration in nanoseconds subtracted.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param nanosToSubtract the nanoseconds to subtract, positive or negative
 * @return a {@code Duration} based on this duration with the specified nanoseconds subtracted, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration minusNanos(long nanosToSubtract) {
 return (nanosToSubtract == Long.MIN_VALUE ? plusNanos(Long.MAX_VALUE).plusNanos(1) : plusNanos(-nanosToSubtract));
 }

 //-----------------------------------------------------------------------
 /**
 * Returns a copy of this duration multiplied by the scalar.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param multiplicand the value to multiply the duration by, positive or negative
 * @return a {@code Duration} based on this duration multiplied by the specified scalar, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration multipliedBy(long multiplicand) {
 if (multiplicand == 0) {
 return ZERO;
 }
 if (multiplicand == 1) {
 return this;
 }
 return create(toBigDecimalSeconds().multiply(BigDecimal.valueOf(multiplicand)));
 }

 /**
 * Returns a copy of this duration divided by the specified value.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param divisor the value to divide the duration by, positive or negative, not zero
 * @return a {@code Duration} based on this duration divided by the specified divisor, not null
 * @throws ArithmeticException if the divisor is zero or if numeric overflow occurs
 */
 public Duration dividedBy(long divisor) {
 if (divisor == 0) {
 throw new ArithmeticException("Cannot divide by zero");
 }
 if (divisor == 1) {
 return this;
 }
 return create(toBigDecimalSeconds().divide(BigDecimal.valueOf(divisor), RoundingMode.DOWN));
 }

 /**
 * Returns number of whole times a specified Duration occurs within this Duration.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param divisor the value to divide the duration by, positive or negative, not null
 * @return number of whole times, rounded toward zero, a specified
 * {@code Duration} occurs within this Duration, may be negative
 * @throws ArithmeticException if the divisor is zero, or if numeric overflow occurs
 * @since 9
 */
 public long dividedBy(Duration divisor) {
 Objects.requireNonNull(divisor, "divisor");
 BigDecimal dividendBigD = toBigDecimalSeconds();
 BigDecimal divisorBigD = divisor.toBigDecimalSeconds();
 return dividendBigD.divideToIntegralValue(divisorBigD).longValueExact();
 }

 /**
 * Converts this duration to the total length in seconds and
 * fractional nanoseconds expressed as a {@code BigDecimal}.
 *
 * @return the total length of the duration in seconds, with a scale of 9, not null
 */
 private BigDecimal toBigDecimalSeconds() {
 return BigDecimal.valueOf(seconds).add(BigDecimal.valueOf(nanos, 9));
 }

 /**
 * Creates an instance of {@code Duration} from a number of seconds.
 *
 * @param seconds the number of seconds, up to scale 9, positive or negative
 * @return a {@code Duration}, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 private static Duration create(BigDecimal seconds) {
 BigInteger nanos = seconds.movePointRight(9).toBigIntegerExact();
 BigInteger[] divRem = nanos.divideAndRemainder(BI_NANOS_PER_SECOND);
 if (divRem[0].bitLength() > 63) {
 throw new ArithmeticException("Exceeds capacity of Duration: " + nanos);
 }
 return ofSeconds(divRem[0].longValue(), divRem[1].intValue());
 }

 //-----------------------------------------------------------------------
 /**
 * Returns a copy of this duration with the length negated.
 * <p>
 * This method swaps the sign of the total length of this duration.
 * For example, {@code PT1.3S} will be returned as {@code PT-1.3S}.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return a {@code Duration} based on this duration with the amount negated, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration negated() {
 return multipliedBy(-1);
 }

 /**
 * Returns a copy of this duration with a positive length.
 * <p>
 * This method returns a positive duration by effectively removing the sign from any negative total length.
 * For example, {@code PT-1.3S} will be returned as {@code PT1.3S}.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return a {@code Duration} based on this duration with an absolute length, not null
 * @throws ArithmeticException if numeric overflow occurs
 */
 public Duration abs() {
 return isNegative() ? negated() : this;
 }

 //-------------------------------------------------------------------------
 /**
 * Adds this duration to the specified temporal object.
 * <p>
 * This returns a temporal object of the same observable type as the input
 * with this duration added.
 * <p>
 * In most cases, it is clearer to reverse the calling pattern by using
 * {@link Temporal#plus(TemporalAmount)}.
 * <pre>
 * // these two lines are equivalent, but the second approach is recommended
 * dateTime = thisDuration.addTo(dateTime);
 * dateTime = dateTime.plus(thisDuration);
 * </pre>
 * <p>
 * The calculation will add the seconds, then nanos.
 * Only non-zero amounts will be added.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param temporal the temporal object to adjust, not null
 * @return an object of the same type with the adjustment made, not null
 * @throws DateTimeException if unable to add
 * @throws ArithmeticException if numeric overflow occurs
 */
 @Override
 public Temporal addTo(Temporal temporal) {
 if (seconds != 0) {
 temporal = temporal.plus(seconds, SECONDS);
 }
 if (nanos != 0) {
 temporal = temporal.plus(nanos, NANOS);
 }
 return temporal;
 }

 /**
 * Subtracts this duration from the specified temporal object.
 * <p>
 * This returns a temporal object of the same observable type as the input
 * with this duration subtracted.
 * <p>
 * In most cases, it is clearer to reverse the calling pattern by using
 * {@link Temporal#minus(TemporalAmount)}.
 * <pre>
 * // these two lines are equivalent, but the second approach is recommended
 * dateTime = thisDuration.subtractFrom(dateTime);
 * dateTime = dateTime.minus(thisDuration);
 * </pre>
 * <p>
 * The calculation will subtract the seconds, then nanos.
 * Only non-zero amounts will be added.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param temporal the temporal object to adjust, not null
 * @return an object of the same type with the adjustment made, not null
 * @throws DateTimeException if unable to subtract
 * @throws ArithmeticException if numeric overflow occurs
 */
 @Override
 public Temporal subtractFrom(Temporal temporal) {
 if (seconds != 0) {
 temporal = temporal.minus(seconds, SECONDS);
 }
 if (nanos != 0) {
 temporal = temporal.minus(nanos, NANOS);
 }
 return temporal;
 }

 //-----------------------------------------------------------------------
 /**
 * Gets the number of days in this duration.
 * <p>
 * This returns the total number of days in the duration by dividing the
 * number of seconds by 86400.
 * This is based on the standard definition of a day as 24 hours.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return the number of days in the duration, may be negative
 */
 public long toDays() {
 return seconds / SECONDS_PER_DAY;
 }

 /**
 * Gets the number of hours in this duration.
 * <p>
 * This returns the total number of hours in the duration by dividing the
 * number of seconds by 3600.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return the number of hours in the duration, may be negative
 */
 public long toHours() {
 return seconds / SECONDS_PER_HOUR;
 }

 /**
 * Gets the number of minutes in this duration.
 * <p>
 * This returns the total number of minutes in the duration by dividing the
 * number of seconds by 60.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return the number of minutes in the duration, may be negative
 */
 public long toMinutes() {
 return seconds / SECONDS_PER_MINUTE;
 }

 /**
 * Gets the number of seconds in this duration.
 * <p>
 * This returns the total number of whole seconds in the duration.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return the whole seconds part of the length of the duration, positive or negative
 * @since 9
 */
 public long toSeconds() {
 return seconds;
 }

 /**
 * Converts this duration to the total length in milliseconds.
 * <p>
 * If this duration is too large to fit in a {@code long} milliseconds, then an
 * exception is thrown.
 * <p>
 * If this duration has greater than millisecond precision, then the conversion
 * will drop any excess precision information as though the amount in nanoseconds
 * was subject to integer division by one million.
 *
 * @return the total length of the duration in milliseconds
 * @throws ArithmeticException if numeric overflow occurs
 */
 public long toMillis() {
 long tempSeconds = seconds;
 long tempNanos = nanos;
 if (tempSeconds < 0) {
 // change the seconds and nano value to
 // handle Long.MIN_VALUE case
 tempSeconds = tempSeconds + 1;
 tempNanos = tempNanos - NANOS_PER_SECOND;
 }
 long millis = Math.multiplyExact(tempSeconds, 1000);
 millis = Math.addExact(millis, tempNanos / NANOS_PER_MILLI);
 return millis;
 }

 /**
 * Converts this duration to the total length in nanoseconds expressed as a {@code long}.
 * <p>
 * If this duration is too large to fit in a {@code long} nanoseconds, then an
 * exception is thrown.
 *
 * @return the total length of the duration in nanoseconds
 * @throws ArithmeticException if numeric overflow occurs
 */
 public long toNanos() {
 long tempSeconds = seconds;
 long tempNanos = nanos;
 if (tempSeconds < 0) {
 // change the seconds and nano value to
 // handle Long.MIN_VALUE case
 tempSeconds = tempSeconds + 1;
 tempNanos = tempNanos - NANOS_PER_SECOND;
 }
 long totalNanos = Math.multiplyExact(tempSeconds, NANOS_PER_SECOND);
 totalNanos = Math.addExact(totalNanos, tempNanos);
 return totalNanos;
 }

 /**
 * Extracts the number of days in the duration.
 * <p>
 * This returns the total number of days in the duration by dividing the
 * number of seconds by 86400.
 * This is based on the standard definition of a day as 24 hours.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return the number of days in the duration, may be negative
 * @since 9
 */
 public long toDaysPart(){
 return seconds / SECONDS_PER_DAY;
 }

 /**
 * Extracts the number of hours part in the duration.
 * <p>
 * This returns the number of remaining hours when dividing {@link #toHours}
 * by hours in a day.
 * This is based on the standard definition of a day as 24 hours.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return the number of hours part in the duration, may be negative
 * @since 9
 */
 public int toHoursPart(){
 return (int) (toHours() % 24);
 }

 /**
 * Extracts the number of minutes part in the duration.
 * <p>
 * This returns the number of remaining minutes when dividing {@link #toMinutes}
 * by minutes in an hour.
 * This is based on the standard definition of an hour as 60 minutes.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return the number of minutes parts in the duration, may be negative
 * @since 9
 */
 public int toMinutesPart(){
 return (int) (toMinutes() % MINUTES_PER_HOUR);
 }

 /**
 * Extracts the number of seconds part in the duration.
 * <p>
 * This returns the remaining seconds when dividing {@link #toSeconds}
 * by seconds in a minute.
 * This is based on the standard definition of a minute as 60 seconds.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return the number of seconds parts in the duration, may be negative
 * @since 9
 */
 public int toSecondsPart(){
 return (int) (seconds % SECONDS_PER_MINUTE);
 }

 /**
 * Extracts the number of milliseconds part of the duration.
 * <p>
 * This returns the milliseconds part by dividing the number of nanoseconds by 1,000,000.
 * The length of the duration is stored using two fields - seconds and nanoseconds.
 * The nanoseconds part is a value from 0 to 999,999,999 that is an adjustment to
 * the length in seconds.
 * The total duration is defined by calling {@link #getNano()} and {@link #getSeconds()}.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return the number of milliseconds part of the duration.
 * @since 9
 */
 public int toMillisPart(){
 return nanos / 1000_000;
 }

 /**
 * Get the nanoseconds part within seconds of the duration.
 * <p>
 * The length of the duration is stored using two fields - seconds and nanoseconds.
 * The nanoseconds part is a value from 0 to 999,999,999 that is an adjustment to
 * the length in seconds.
 * The total duration is defined by calling {@link #getNano()} and {@link #getSeconds()}.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @return the nanoseconds within the second part of the length of the duration, from 0 to 999,999,999
 * @since 9
 */
 public int toNanosPart(){
 return nanos;
 }


 //-----------------------------------------------------------------------
 /**
 * Returns a copy of this {@code Duration} truncated to the specified unit.
 * <p>
 * Truncating the duration returns a copy of the original with conceptual fields
 * smaller than the specified unit set to zero.
 * For example, truncating with the {@link ChronoUnit#MINUTES MINUTES} unit will
 * round down towards zero to the nearest minute, setting the seconds and
 * nanoseconds to zero.
 * <p>
 * The unit must have a {@linkplain TemporalUnit#getDuration() duration}
 * that divides into the length of a standard day without remainder.
 * This includes all
 * {@linkplain ChronoUnit#isTimeBased() time-based units on {@code ChronoUnit}}
 * and {@link ChronoUnit#DAYS DAYS}. Other ChronoUnits throw an exception.
 * <p>
 * This instance is immutable and unaffected by this method call.
 *
 * @param unit the unit to truncate to, not null
 * @return a {@code Duration} based on this duration with the time truncated, not null
 * @throws DateTimeException if the unit is invalid for truncation
 * @throws UnsupportedTemporalTypeException if the unit is not supported
 * @since 9
 */
 public Duration truncatedTo(TemporalUnit unit) {
 Objects.requireNonNull(unit, "unit");
 if (unit == ChronoUnit.SECONDS && (seconds >= 0 || nanos == 0)) {
 return new Duration(seconds, 0);
 } else if (unit == ChronoUnit.NANOS) {
 return this;
 }
 Duration unitDur = unit.getDuration();
 if (unitDur.getSeconds() > LocalTime.SECONDS_PER_DAY) {
 throw new UnsupportedTemporalTypeException("Unit is too large to be used for truncation");
 }
 long dur = unitDur.toNanos();
 if ((LocalTime.NANOS_PER_DAY % dur) != 0) {
 throw new UnsupportedTemporalTypeException("Unit must divide into a standard day without remainder");
 }
 long nod = (seconds % LocalTime.SECONDS_PER_DAY) * LocalTime.NANOS_PER_SECOND + nanos;
 long result = (nod / dur) * dur;
 return plusNanos(result - nod);
 }

 //-----------------------------------------------------------------------
 /**
 * Compares this duration to the specified {@code Duration}.
 * <p>
 * The comparison is based on the total length of the durations.
 * It is "consistent with equals", as defined by {@link Comparable}.
 *
 * @param otherDuration the other duration to compare to, not null
 * @return the comparator value, negative if less, positive if greater
 */
 @Override
 public int compareTo(Duration otherDuration) {
 int cmp = Long.compare(seconds, otherDuration.seconds);
 if (cmp != 0) {
 return cmp;
 }
 return nanos - otherDuration.nanos;
 }

 //-----------------------------------------------------------------------
 /**
 * Checks if this duration is equal to the specified {@code Duration}.
 * <p>
 * The comparison is based on the total length of the durations.
 *
 * @param otherDuration the other duration, null returns false
 * @return true if the other duration is equal to this one
 */
 @Override
 public boolean equals(Object otherDuration) {
 if (this == otherDuration) {
 return true;
 }
 if (otherDuration instanceof Duration) {
 Duration other = (Duration) otherDuration;
 return this.seconds == other.seconds &&
 this.nanos == other.nanos;
 }
 return false;
 }

 /**
 * A hash code for this duration.
 *
 * @return a suitable hash code
 */
 @Override
 public int hashCode() {
 return ((int) (seconds ^ (seconds >>> 32))) + (51 * nanos);
 }

 //-----------------------------------------------------------------------
 /**
 * A string representation of this duration using ISO-8601 seconds
 * based representation, such as {@code PT8H6M12.345S}.
 * <p>
 * The format of the returned string will be {@code PTnHnMnS}, where n is
 * the relevant hours, minutes or seconds part of the duration.
 * Any fractional seconds are placed after a decimal point in the seconds section.
 * If a section has a zero value, it is omitted.
 * The hours, minutes and seconds will all have the same sign.
 * <p>
 * Examples:
 * <pre>
 * "20.345 seconds" -- "PT20.345S
 * "15 minutes" (15 * 60 seconds) -- "PT15M"
 * "10 hours" (10 * 3600 seconds) -- "PT10H"
 * "2 days" (2 * 86400 seconds) -- "PT48H"
 * </pre>
 * Note that multiples of 24 hours are not output as days to avoid confusion
 * with {@code Period}.
 *
 * @return an ISO-8601 representation of this duration, not null
 */
 @Override
 public String toString() {
 if (this == ZERO) {
 return "PT0S";
 }
 long effectiveTotalSecs = seconds;
 if (seconds < 0 && nanos > 0) {
 effectiveTotalSecs++;
 }
 long hours = effectiveTotalSecs / SECONDS_PER_HOUR;
 int minutes = (int) ((effectiveTotalSecs % SECONDS_PER_HOUR) / SECONDS_PER_MINUTE);
 int secs = (int) (effectiveTotalSecs % SECONDS_PER_MINUTE);
 StringBuilder buf = new StringBuilder(24);
 buf.append("PT");
 if (hours != 0) {
 buf.append(hours).append('H');
 }
 if (minutes != 0) {
 buf.append(minutes).append('M');
 }
 if (secs == 0 && nanos == 0 && buf.length() > 2) {
 return buf.toString();
 }
 if (seconds < 0 && nanos > 0) {
 if (secs == 0) {
 buf.append("-0");
 } else {
 buf.append(secs);
 }
 } else {
 buf.append(secs);
 }
 if (nanos > 0) {
 int pos = buf.length();
 if (seconds < 0) {
 buf.append(2 * NANOS_PER_SECOND - nanos);
 } else {
 buf.append(nanos + NANOS_PER_SECOND);
 }
 while (buf.charAt(buf.length() - 1) == '0') {
 buf.setLength(buf.length() - 1);
 }
 buf.setCharAt(pos, '.');
 }
 buf.append('S');
 return buf.toString();
 }

 //-----------------------------------------------------------------------
 /**
 * Writes the object using a
 * <a href="{@docRoot}/serialized-form.html#java.time.Ser">dedicated serialized form</a>.
 * @serialData
 * <pre>
 * out.writeByte(1); // identifies a Duration
 * out.writeLong(seconds);
 * out.writeInt(nanos);
 * </pre>
 *
 * @return the instance of {@code Ser}, not null
 */
 private Object writeReplace() {
 return new Ser(Ser.DURATION_TYPE, this);
 }

 /**
 * Defend against malicious streams.
 *
 * @param s the stream to read
 * @throws InvalidObjectException always
 */
 private void readObject(ObjectInputStream s) throws InvalidObjectException {
 throw new InvalidObjectException("Deserialization via serialization delegate");
 }

 void writeExternal(DataOutput out) throws IOException {
 out.writeLong(seconds);
 out.writeInt(nanos);
 }

 static Duration readExternal(DataInput in) throws IOException {
 long seconds = in.readLong();
 int nanos = in.readInt();
 return Duration.ofSeconds(seconds, nanos);
 }

}