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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 
*
 
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* FITNESS FOR A PARTICULAR PURPOSE.
  
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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.
 
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*
  
* Redistributions in binary form must reproduce the above copyright notice,
 
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this list of conditions and the following disclaimer in the documentation
 
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and/or other materials provided with the distribution.
 
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* Neither the name of JSR-310 nor the names of its contributors
 
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may be used to endorse or promote products derived from this software
 
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package java.time;

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.Arrays;
import java.util.Collections;
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/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 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 the 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 an {@code long}.
     
* The number of seconds must parse to an {@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"
     
*
    
"P-6H3M"-- parses as "-6 hours and +3 minutes"
     
*
    
"-P6H3M"-- parses as "-6 hours and -3 minutes"
     
*
    
"-P-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 = PATTERN.matcher(text);
        
if (matcher.matches()) {
            
// check for letter T but no time sections
            
if ("T".equals(matcher.group(3)) == false) {
                
boolean negate = "-".equals(matcher.group(1));
                
String dayMatch = matcher.group(2);
                
String hourMatch = matcher.group(4);
                
String minuteMatch = matcher.group(5);
                
String secondMatch = matcher.group(6);
                
String fractionMatch = matcher.group(7);
                
if (dayMatch != null || hourMatch != null || minuteMatch != null || secondMatch != null) {
                    
long daysAsSecs = parseNumber(text, dayMatch, SECONDS_PER_DAY, "days");
                    
long hoursAsSecs = parseNumber(text, hourMatch, SECONDS_PER_HOUR, "hours");
                    
long minsAsSecs = parseNumber(text, minuteMatch, SECONDS_PER_MINUTE, "minutes");
                    
long seconds = parseNumber(text, secondMatch, 1, "seconds");
                    
int nanos = parseFraction(text,
  
fractionMatch, seconds < 0 ? -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 long parseNumber(CharSequence text, String parsed, int multiplier, String errorText) {
        
// regex limits to [-+]?[0-9]+
        
if (parsed == null) {
            
return 0;
        
}
        
try {
            
long val = Long.parseLong(parsed);
            
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, String parsed, int negate) {
        
// regex limits to [0-9]{0,9}
        
if (parsed == null || parsed.length() == 0) {
            
return 0;
        
}
        
try {
            
parsed = (parsed + "000000000").substring(0, 9);
            
return Integer.parseInt(parsed) * 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
 
 
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 =
                
Collections.unmodifiableList(Arrays.<TemporalUnit>asList(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
 
.
     
* <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
 
.
     
* <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(toSeconds().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(toSeconds().divide(BigDecimal.valueOf(divisor), RoundingMode.DOWN));
     
}

    
/**
     
* 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 toSeconds() {
        
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;
    
}

    
/**
     
* 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 millis = Math.multiplyExact(seconds, 1000);
        
millis = Math.addExact(millis, nanos / 1000_000);
        
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 totalNanos = Math.multiplyExact(seconds, NANOS_PER_SECOND);
        
totalNanos = Math.addExact(totalNanos, nanos);
        
return totalNanos;
    
}

    
//-----------------------------------------------------------------------
    
/**
     
* 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 i 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 hours = seconds / SECONDS_PER_HOUR;
        
int minutes = (int) ((seconds % SECONDS_PER_HOUR) / SECONDS_PER_MINUTE);
        
int secs = (int) (seconds % 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 (secs < 0 && nanos > 0) {
            
if (secs == -1) {
                
buf.append("-0");
            
} else {
                
buf.append(secs + 1);
            
}
        
} else {
            
buf.append(secs);
        
}
        
if (nanos > 0) {
            
int pos = buf.length();
            
if (secs < 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="../../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);
    
}

}