Class Period
 All Implemented Interfaces:
Serializable
,ChronoPeriod
,TemporalAmount
This class models a quantity or amount of time in terms of years, months and days.
See Duration
for the timebased equivalent to this class.
Durations and periods differ in their treatment of daylight savings time
when added to ZonedDateTime
. A Duration
will add an exact
number of seconds, thus a duration of one day is always exactly 24 hours.
By contrast, a Period
will add a conceptual day, trying to maintain
the local time.
For example, consider adding a period of one day and a duration of one day to
18:00 on the evening before a daylight savings gap. The Period
will add
the conceptual day and result in a ZonedDateTime
at 18:00 the following day.
By contrast, the Duration
will add exactly 24 hours, resulting in a
ZonedDateTime
at 19:00 the following day (assuming a one hour DST gap).
The supported units of a period are YEARS
,
MONTHS
and DAYS
.
All three fields are always present, but may be set to zero.
The ISO8601 calendar system is the modern civil calendar system used today in most of the world. It is equivalent to the proleptic Gregorian calendar system, in which today's rules for leap years are applied for all time.
The period is modeled as a directed amount of time, meaning that individual parts of the period may be negative.
This is a valuebased
class; programmers should treat instances that are
equal as interchangeable and should not
use instances for synchronization, or unpredictable behavior may
occur. For example, in a future release, synchronization may fail.
The equals
method should be used for comparisons.
 Implementation Requirements:
 This class is immutable and threadsafe.
 Since:
 1.8
 See Also:

Field Summary

Method Summary
Modifier and TypeMethodDescriptionAdds this period to the specified temporal object.static Period
Obtains aPeriod
consisting of the number of years, months, and days between two dates.boolean
Checks if this period is equal to another period.static Period
from
(TemporalAmount amount) Obtains an instance ofPeriod
from a temporal amount.long
get
(TemporalUnit unit) Gets the value of the requested unit.Gets the chronology of this period, which is the ISO calendar system.int
getDays()
Gets the amount of days of this period.int
Gets the amount of months of this period.getUnits()
Gets the set of units supported by this period.int
getYears()
Gets the amount of years of this period.int
hashCode()
A hash code for this period.boolean
Checks if any of the three units of this period are negative.boolean
isZero()
Checks if all three units of this period are zero.minus
(TemporalAmount amountToSubtract) Returns a copy of this period with the specified period subtracted.minusDays
(long daysToSubtract) Returns a copy of this period with the specified days subtracted.minusMonths
(long monthsToSubtract) Returns a copy of this period with the specified months subtracted.minusYears
(long yearsToSubtract) Returns a copy of this period with the specified years subtracted.multipliedBy
(int scalar) Returns a new instance with each element in this period multiplied by the specified scalar.negated()
Returns a new instance with each amount in this period negated.Returns a copy of this period with the years and months normalized.static Period
of
(int years, int months, int days) Obtains aPeriod
representing a number of years, months and days.static Period
ofDays
(int days) Obtains aPeriod
representing a number of days.static Period
ofMonths
(int months) Obtains aPeriod
representing a number of months.static Period
ofWeeks
(int weeks) Obtains aPeriod
representing a number of weeks.static Period
ofYears
(int years) Obtains aPeriod
representing a number of years.static Period
parse
(CharSequence text) Obtains aPeriod
from a text string such asPnYnMnD
.plus
(TemporalAmount amountToAdd) Returns a copy of this period with the specified period added.plusDays
(long daysToAdd) Returns a copy of this period with the specified days added.plusMonths
(long monthsToAdd) Returns a copy of this period with the specified months added.plusYears
(long yearsToAdd) Returns a copy of this period with the specified years added.subtractFrom
(Temporal temporal) Subtracts this period from the specified temporal object.toString()
Outputs this period as aString
, such asP6Y3M1D
.long
Gets the total number of months in this period.withDays
(int days) Returns a copy of this period with the specified amount of days.withMonths
(int months) Returns a copy of this period with the specified amount of months.withYears
(int years) Returns a copy of this period with the specified amount of years.

Field Details

ZERO
A constant for a period of zero.


Method Details

ofYears
Obtains aPeriod
representing a number of years.The resulting period will have the specified years. The months and days units will be zero.
 Parameters:
years
 the number of years, positive or negative Returns:
 the period of years, not null

ofMonths
Obtains aPeriod
representing a number of months.The resulting period will have the specified months. The years and days units will be zero.
 Parameters:
months
 the number of months, positive or negative Returns:
 the period of months, not null

ofWeeks
Obtains aPeriod
representing a number of weeks.The resulting period will be daybased, with the amount of days equal to the number of weeks multiplied by 7. The years and months units will be zero.
 Parameters:
weeks
 the number of weeks, positive or negative Returns:
 the period, with the input weeks converted to days, not null

ofDays
Obtains aPeriod
representing a number of days.The resulting period will have the specified days. The years and months units will be zero.
 Parameters:
days
 the number of days, positive or negative Returns:
 the period of days, not null

of
Obtains aPeriod
representing a number of years, months and days.This creates an instance based on years, months and days.
 Parameters:
years
 the amount of years, may be negativemonths
 the amount of months, may be negativedays
 the amount of days, may be negative Returns:
 the period of years, months and days, not null

from
Obtains an instance ofPeriod
from a temporal amount.This obtains a period based on the specified amount. A
TemporalAmount
represents an amount of time, which may be datebased or timebased, which this factory extracts to aPeriod
.The conversion loops around the set of units from the amount and uses the
YEARS
,MONTHS
andDAYS
units to create a period. If any other units are found then an exception is thrown.If the amount is a
ChronoPeriod
then it must use the ISO chronology. Parameters:
amount
 the temporal amount to convert, not null Returns:
 the equivalent period, not null
 Throws:
DateTimeException
 if unable to convert to aPeriod
ArithmeticException
 if the amount of years, months or days exceeds an int

parse
Obtains aPeriod
from a text string such asPnYnMnD
.This will parse the string produced by
toString()
which is based on the ISO8601 period formatsPnYnMnD
andPnW
.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. At least one of the four sections must be present. The sections have suffixes in ASCII of "Y", "M", "W" and "D" for years, months, weeks and days, accepted in upper or lower case. The suffixes must occur in order. The number part of each section must consist of ASCII digits. The number may be prefixed by the ASCII negative or positive symbol. The number must parse to an
int
.The leading plus/minus sign, and negative values for other units are not part of the ISO8601 standard. In addition, ISO8601 does not permit mixing between the
PnYnMnD
andPnW
formats. Any weekbased input is multiplied by 7 and treated as a number of days.For example, the following are valid inputs:
"P2Y"  Period.ofYears(2) "P3M"  Period.ofMonths(3) "P4W"  Period.ofWeeks(4) "P5D"  Period.ofDays(5) "P1Y2M3D"  Period.of(1, 2, 3) "P1Y2M3W4D"  Period.of(1, 2, 25) "P1Y2M"  Period.of(1, 2, 0) "P1Y2M"  Period.of(1, 2, 0)
 Parameters:
text
 the text to parse, not null Returns:
 the parsed period, not null
 Throws:
DateTimeParseException
 if the text cannot be parsed to a period

between
Obtains aPeriod
consisting of the number of years, months, and days between two dates.The start date is included, but the end date is not. The period is calculated by removing complete months, then calculating the remaining number of days, adjusting to ensure that both have the same sign. The number of months is then split into years and months based on a 12 month year. A month is considered if the end dayofmonth is greater than or equal to the start dayofmonth. For example, from
20100115
to20110318
is one year, two months and three days.The result of this method can be a negative period if the end is before the start. The negative sign will be the same in each of year, month and day.
 Parameters:
startDateInclusive
 the start date, inclusive, not nullendDateExclusive
 the end date, exclusive, not null Returns:
 the period between this date and the end date, not null
 See Also:

get
Gets the value of the requested unit.This returns a value for each of the three supported units,
YEARS
,MONTHS
andDAYS
. All other units throw an exception. Specified by:
get
in interfaceChronoPeriod
 Specified by:
get
in interfaceTemporalAmount
 Parameters:
unit
 theTemporalUnit
for which to return the value Returns:
 the long value of the unit
 Throws:
DateTimeException
 if the unit is not supportedUnsupportedTemporalTypeException
 if the unit is not supported

getUnits
Gets the set of units supported by this period.The supported units are
YEARS
,MONTHS
andDAYS
. They are returned in the order years, months, days.This set can be used in conjunction with
get(TemporalUnit)
to access the entire state of the period. Specified by:
getUnits
in interfaceChronoPeriod
 Specified by:
getUnits
in interfaceTemporalAmount
 Returns:
 a list containing the years, months and days units, not null

getChronology
Gets the chronology of this period, which is the ISO calendar system.The
Chronology
represents the calendar system in use. The ISO8601 calendar system is the modern civil calendar system used today in most of the world. It is equivalent to the proleptic Gregorian calendar system, in which today's rules for leap years are applied for all time. Specified by:
getChronology
in interfaceChronoPeriod
 Returns:
 the ISO chronology, not null

isZero
public boolean isZero()Checks if all three units of this period are zero.A zero period has the value zero for the years, months and days units.
 Specified by:
isZero
in interfaceChronoPeriod
 Returns:
 true if this period is zerolength

isNegative
public boolean isNegative()Checks if any of the three units of this period are negative.This checks whether the years, months or days units are less than zero.
 Specified by:
isNegative
in interfaceChronoPeriod
 Returns:
 true if any unit of this period is negative

getYears
public int getYears()Gets the amount of years of this period.This returns the years unit.
The months unit is not automatically normalized with the years unit. This means that a period of "15 months" is different to a period of "1 year and 3 months".
 Returns:
 the amount of years of this period, may be negative

getMonths
public int getMonths()Gets the amount of months of this period.This returns the months unit.
The months unit is not automatically normalized with the years unit. This means that a period of "15 months" is different to a period of "1 year and 3 months".
 Returns:
 the amount of months of this period, may be negative

getDays
public int getDays()Gets the amount of days of this period.This returns the days unit.
 Returns:
 the amount of days of this period, may be negative

withYears
Returns a copy of this period with the specified amount of years.This sets the amount of the years unit in a copy of this period. The months and days units are unaffected.
The months unit is not automatically normalized with the years unit. This means that a period of "15 months" is different to a period of "1 year and 3 months".
This instance is immutable and unaffected by this method call.
 Parameters:
years
 the years to represent, may be negative Returns:
 a
Period
based on this period with the requested years, not null

withMonths
Returns a copy of this period with the specified amount of months.This sets the amount of the months unit in a copy of this period. The years and days units are unaffected.
The months unit is not automatically normalized with the years unit. This means that a period of "15 months" is different to a period of "1 year and 3 months".
This instance is immutable and unaffected by this method call.
 Parameters:
months
 the months to represent, may be negative Returns:
 a
Period
based on this period with the requested months, not null

withDays
Returns a copy of this period with the specified amount of days.This sets the amount of the days unit in a copy of this period. The years and months units are unaffected.
This instance is immutable and unaffected by this method call.
 Parameters:
days
 the days to represent, may be negative Returns:
 a
Period
based on this period with the requested days, not null

plus
Returns a copy of this period with the specified period added.This operates separately on the years, months and days. No normalization is performed.
For example, "1 year, 6 months and 3 days" plus "2 years, 2 months and 2 days" returns "3 years, 8 months and 5 days".
The specified amount is typically an instance of
Period
. Other types are interpreted usingfrom(TemporalAmount)
.This instance is immutable and unaffected by this method call.
 Specified by:
plus
in interfaceChronoPeriod
 Parameters:
amountToAdd
 the amount to add, not null Returns:
 a
Period
based on this period with the requested period added, not null  Throws:
DateTimeException
 if the specified amount has a nonISO chronology or contains an invalid unitArithmeticException
 if numeric overflow occurs

plusYears
Returns a copy of this period with the specified years added.This adds the amount to the years unit in a copy of this period. The months and days units are unaffected. For example, "1 year, 6 months and 3 days" plus 2 years returns "3 years, 6 months and 3 days".
This instance is immutable and unaffected by this method call.
 Parameters:
yearsToAdd
 the years to add, positive or negative Returns:
 a
Period
based on this period with the specified years added, not null  Throws:
ArithmeticException
 if numeric overflow occurs

plusMonths
Returns a copy of this period with the specified months added.This adds the amount to the months unit in a copy of this period. The years and days units are unaffected. For example, "1 year, 6 months and 3 days" plus 2 months returns "1 year, 8 months and 3 days".
This instance is immutable and unaffected by this method call.
 Parameters:
monthsToAdd
 the months to add, positive or negative Returns:
 a
Period
based on this period with the specified months added, not null  Throws:
ArithmeticException
 if numeric overflow occurs

plusDays
Returns a copy of this period with the specified days added.This adds the amount to the days unit in a copy of this period. The years and months units are unaffected. For example, "1 year, 6 months and 3 days" plus 2 days returns "1 year, 6 months and 5 days".
This instance is immutable and unaffected by this method call.
 Parameters:
daysToAdd
 the days to add, positive or negative Returns:
 a
Period
based on this period with the specified days added, not null  Throws:
ArithmeticException
 if numeric overflow occurs

minus
Returns a copy of this period with the specified period subtracted.This operates separately on the years, months and days. No normalization is performed.
For example, "1 year, 6 months and 3 days" minus "2 years, 2 months and 2 days" returns "1 years, 4 months and 1 day".
The specified amount is typically an instance of
Period
. Other types are interpreted usingfrom(TemporalAmount)
.This instance is immutable and unaffected by this method call.
 Specified by:
minus
in interfaceChronoPeriod
 Parameters:
amountToSubtract
 the amount to subtract, not null Returns:
 a
Period
based on this period with the requested period subtracted, not null  Throws:
DateTimeException
 if the specified amount has a nonISO chronology or contains an invalid unitArithmeticException
 if numeric overflow occurs

minusYears
Returns a copy of this period with the specified years subtracted.This subtracts the amount from the years unit in a copy of this period. The months and days units are unaffected. For example, "1 year, 6 months and 3 days" minus 2 years returns "1 years, 6 months and 3 days".
This instance is immutable and unaffected by this method call.
 Parameters:
yearsToSubtract
 the years to subtract, positive or negative Returns:
 a
Period
based on this period with the specified years subtracted, not null  Throws:
ArithmeticException
 if numeric overflow occurs

minusMonths
Returns a copy of this period with the specified months subtracted.This subtracts the amount from the months unit in a copy of this period. The years and days units are unaffected. For example, "1 year, 6 months and 3 days" minus 2 months returns "1 year, 4 months and 3 days".
This instance is immutable and unaffected by this method call.
 Parameters:
monthsToSubtract
 the years to subtract, positive or negative Returns:
 a
Period
based on this period with the specified months subtracted, not null  Throws:
ArithmeticException
 if numeric overflow occurs

minusDays
Returns a copy of this period with the specified days subtracted.This subtracts the amount from the days unit in a copy of this period. The years and months units are unaffected. For example, "1 year, 6 months and 3 days" minus 2 days returns "1 year, 6 months and 1 day".
This instance is immutable and unaffected by this method call.
 Parameters:
daysToSubtract
 the months to subtract, positive or negative Returns:
 a
Period
based on this period with the specified days subtracted, not null  Throws:
ArithmeticException
 if numeric overflow occurs

multipliedBy
Returns a new instance with each element in this period multiplied by the specified scalar.This returns a period with each of the years, months and days units individually multiplied. For example, a period of "2 years, 3 months and 4 days" multiplied by 3 will return "6 years, 9 months and 12 days". No normalization is performed.
 Specified by:
multipliedBy
in interfaceChronoPeriod
 Parameters:
scalar
 the scalar to multiply by, not null Returns:
 a
Period
based on this period with the amounts multiplied by the scalar, not null  Throws:
ArithmeticException
 if numeric overflow occurs

negated
Returns a new instance with each amount in this period negated.This returns a period with each of the years, months and days units individually negated. For example, a period of "2 years, 3 months and 4 days" will be negated to "2 years, 3 months and 4 days". No normalization is performed.
 Specified by:
negated
in interfaceChronoPeriod
 Returns:
 a
Period
based on this period with the amounts negated, not null  Throws:
ArithmeticException
 if numeric overflow occurs, which only happens if one of the units has the valueInteger.MIN_VALUE

normalized
Returns a copy of this period with the years and months normalized.This normalizes the years and months units, leaving the days unit unchanged. The months unit is adjusted to have an absolute value less than 12, with the years unit being adjusted to compensate. For example, a period of "1 Year and 15 months" will be normalized to "2 years and 3 months".
The sign of the years and months units will be the same after normalization. For example, a period of "1 year and 25 months" will be normalized to "1 year and 1 month".
This instance is immutable and unaffected by this method call.
 Specified by:
normalized
in interfaceChronoPeriod
 Returns:
 a
Period
based on this period with excess months normalized to years, not null  Throws:
ArithmeticException
 if numeric overflow occurs

toTotalMonths
public long toTotalMonths()Gets the total number of months in this period.This returns the total number of months in the period by multiplying the number of years by 12 and adding the number of months.
This instance is immutable and unaffected by this method call.
 Returns:
 the total number of months in the period, may be negative

addTo
Adds this period to the specified temporal object.This returns a temporal object of the same observable type as the input with this period added. If the temporal has a chronology, it must be the ISO chronology.
In most cases, it is clearer to reverse the calling pattern by using
Temporal.plus(TemporalAmount)
.// these two lines are equivalent, but the second approach is recommended dateTime = thisPeriod.addTo(dateTime); dateTime = dateTime.plus(thisPeriod);
The calculation operates as follows. First, the chronology of the temporal is checked to ensure it is ISO chronology or null. Second, if the months are zero, the years are added if nonzero, otherwise the combination of years and months is added if nonzero. Finally, any days are added.
This approach ensures that a partial period can be added to a partial date. For example, a period of years and/or months can be added to a
YearMonth
, but a period including days cannot. The approach also adds years and months together when necessary, which ensures correct behaviour at the end of the month.This instance is immutable and unaffected by this method call.
 Specified by:
addTo
in interfaceChronoPeriod
 Specified by:
addTo
in interfaceTemporalAmount
 Parameters:
temporal
 the temporal object to adjust, not null Returns:
 an object of the same type with the adjustment made, not null
 Throws:
DateTimeException
 if unable to addArithmeticException
 if numeric overflow occurs

subtractFrom
Subtracts this period from the specified temporal object.This returns a temporal object of the same observable type as the input with this period subtracted. If the temporal has a chronology, it must be the ISO chronology.
In most cases, it is clearer to reverse the calling pattern by using
Temporal.minus(TemporalAmount)
.// these two lines are equivalent, but the second approach is recommended dateTime = thisPeriod.subtractFrom(dateTime); dateTime = dateTime.minus(thisPeriod);
The calculation operates as follows. First, the chronology of the temporal is checked to ensure it is ISO chronology or null. Second, if the months are zero, the years are subtracted if nonzero, otherwise the combination of years and months is subtracted if nonzero. Finally, any days are subtracted.
This approach ensures that a partial period can be subtracted from a partial date. For example, a period of years and/or months can be subtracted from a
YearMonth
, but a period including days cannot. The approach also subtracts years and months together when necessary, which ensures correct behaviour at the end of the month.This instance is immutable and unaffected by this method call.
 Specified by:
subtractFrom
in interfaceChronoPeriod
 Specified by:
subtractFrom
in interfaceTemporalAmount
 Parameters:
temporal
 the temporal object to adjust, not null Returns:
 an object of the same type with the adjustment made, not null
 Throws:
DateTimeException
 if unable to subtractArithmeticException
 if numeric overflow occurs

equals
Checks if this period is equal to another period.The comparison is based on the type
Period
and each of the three amounts. To be equal, the years, months and days units must be individually equal. Note that this means that a period of "15 Months" is not equal to a period of "1 Year and 3 Months". Specified by:
equals
in interfaceChronoPeriod
 Overrides:
equals
in classObject
 Parameters:
obj
 the object to check, null returns false Returns:
 true if this is equal to the other period
 See Also:

hashCode
public int hashCode()A hash code for this period. Specified by:
hashCode
in interfaceChronoPeriod
 Overrides:
hashCode
in classObject
 Returns:
 a suitable hash code
 See Also:

toString
Outputs this period as aString
, such asP6Y3M1D
.The output will be in the ISO8601 period format. A zero period will be represented as zero days, 'P0D'.
 Specified by:
toString
in interfaceChronoPeriod
 Overrides:
toString
in classObject
 Returns:
 a string representation of this period, not null
