Period (ThreeTen backport for java.time package 1.0.0 API)

java.lang.Object
- java.time.chrono.ChronoPeriod
- - java.time.Period

All Implemented Interfaces:

java.io.Serializable, TemporalAmount
```
public final class Period
extends ChronoPeriod
implements java.io.Serializable
```
A date-based amount of time, such as '2 years, 3 months and 4 days'.
This class models a quantity or amount of time in terms of years, months and days. See Duration for the time-based equivalent to this class.
Durations and period 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 period may be used with any calendar system. The meaning of a "year" or "month" is only applied when the object is added to a date.
The period is modeled as a directed amount of time, meaning that individual parts of the period may be negative.
The months and years fields may be normalized. The normalization assumes a 12 month year, so is not appropriate for all calendar systems.
Specification for implementors
This class is immutable and thread-safe.

See Also:
Serialized Form

Field Summary

Fields
Modifier and Type Field and Description

static Period ZERO
A constant for a period of zero.

Fields
Modifier and Type	Field and Description
`static Period`	`ZERO` A constant for a period of zero.

Method Summary

Methods
Modifier and Type	Method and Description
`Temporal`	`addTo(Temporal temporal)` Adds this period to the specified temporal object.
`static Period`	`between(LocalDate startDate, LocalDate endDate)` Obtains a `Period` consisting of the number of years, months, and days between two dates.
`boolean`	`equals(java.lang.Object obj)` Checks if this period is equal to another period.
`static Period`	`from(TemporalAmount amount)` Obtains an instance of `Period` from a temporal amount.
`long`	`get(TemporalUnit unit)` Gets the value of the requested unit.
`Chronology`	`getChronology()` Gets the chronology that defines the meaning of the supported units.
`int`	`getDays()` Gets the amount of days of this period.
`int`	`getMonths()` Gets the amount of months of this period.
`java.util.List<TemporalUnit>`	`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`	`isNegative()` Checks if any of the three units of this period are negative.
`boolean`	`isZero()` Checks if all three units of this period are zero.
`Period`	`minus(TemporalAmount amountToSubtract)` Returns a copy of this period with the specified amount subtracted.
`Period`	`minusDays(long daysToSubtract)` Returns a copy of this period with the specified days subtracted.
`Period`	`minusMonths(long monthsToSubtract)` Returns a copy of this period with the specified months subtracted.
`Period`	`minusYears(long yearsToSubtract)` Returns a copy of this period with the specified years subtracted.
`Period`	`multipliedBy(int scalar)` Returns a new instance with each element in this period multiplied by the specified scalar.
`Period`	`negated()` Returns a new instance with each amount in this period negated.
`Period`	`normalized()` Returns a copy of this period with the years and months normalized using a 12 month year.
`static Period`	`of(int years, int months, int days)` Obtains a `Period` representing a number of years, months and days.
`static Period`	`ofDays(int days)` Obtains a `Period` representing a number of days.
`static Period`	`ofMonths(int months)` Obtains a `Period` representing a number of months.
`static Period`	`ofWeeks(int weeks)` Obtains a `Period` representing a number of weeks.
`static Period`	`ofYears(int years)` Obtains a `Period` representing a number of years.
`static Period`	`parse(java.lang.CharSequence text)` Obtains a `Period` from a text string such as `PnYnMnD`.
`Period`	`plus(TemporalAmount amountToAdd)` Returns a copy of this period with the specified amount added.
`Period`	`plusDays(long daysToAdd)` Returns a copy of this period with the specified days added.
`Period`	`plusMonths(long monthsToAdd)` Returns a copy of this period with the specified months added.
`Period`	`plusYears(long yearsToAdd)` Returns a copy of this period with the specified years added.
`Temporal`	`subtractFrom(Temporal temporal)` Subtracts this period from the specified temporal object.
`java.lang.String`	`toString()` Outputs this period as a `String`, such as `P6Y3M1D`.
`long`	`toTotalMonths()` Gets the total number of months in this period using a 12 month year.
`Period`	`withDays(int days)` Returns a copy of this period with the specified amount of days.
`Period`	`withMonths(int months)` Returns a copy of this period with the specified amount of months.
`Period`	`withYears(int years)` Returns a copy of this period with the specified amount of years.

Methods inherited from class java.time.chrono.ChronoPeriod
between

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - ZERO
```
public static final Period ZERO
```
    A constant for a period of zero.
- Method Detail
  - ofYears
```
public static Period ofYears(int years)
```
    Obtains a Period 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
```
public static Period ofMonths(int months)
```
    Obtains a Period 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
```
public static Period ofWeeks(int weeks)
```
    Obtains a Period representing a number of weeks.
    The resulting period will have days equal to the weeks multiplied by seven. The years and months units will be zero.
    
    Parameters:
    weeks - the number of weeks, positive or negative
    
    Returns:
    the period of days, not null
  - ofDays
```
public static Period ofDays(int days)
```
    Obtains a Period 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
```
public static Period of(int years,
        int months,
        int days)
```
    Obtains a Period 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 negative
    months - the amount of months, may be negative
    days - the amount of days, may be negative
    
    Returns:
    the period of years, months and days, not null
  - from
```
public static Period from(TemporalAmount amount)
```
    Obtains an instance of Period from a temporal amount.
    This obtains a period based on the specified amount. A TemporalAmount represents an amount of time, which may be date-based or time-based, which this factory extracts to a Period.
    The conversion loops around the set of units from the amount and uses the YEARS, MONTHS and DAYS 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 a Period
    
    java.lang.ArithmeticException - if the amount of years, months or days exceeds an int
  - between
```
public static Period between(LocalDate startDate,
             LocalDate endDate)
```
    Obtains a Period 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 day-of-month is greater than or equal to the start day-of-month. For example, from 2010-01-15 to 2011-03-18 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:
    startDate - the start date, inclusive, not null
    endDate - the end date, exclusive, not null
    
    Returns:
    the period between this date and the end date, not null
    See Also:
    ChronoLocalDate.until(ChronoLocalDate)
  - parse
```
public static Period parse(java.lang.CharSequence text)
```
    Obtains a Period from a text string such as PnYnMnD.
    This will parse the string produced by toString() which is based on the ISO-8601 period formats PnYnMnD and PnW.
    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 ISO-8601 standard. In addition, ISO-8601 does not permit mixing between the PnYnMnD and PnW formats. Any week-based 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)
   "P-1Y2M"          -- 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
  - getUnits
```
public java.util.List<TemporalUnit> getUnits()
```
    Description copied from class: ChronoPeriod
    
    Gets the set of units supported by this period.
    The supported units are chronology specific. They will typically be YEARS, MONTHS and DAYS. They are returned in order from largest to smallest.
    This set can be used in conjunction with ChronoPeriod.get(TemporalUnit) to access the entire state of the period.
    
    Specified by:
    
    getUnits in interface TemporalAmount
    
    Specified by:
    
    getUnits in class ChronoPeriod
    
    Returns:
    a list containing the supported units, not null
  - getChronology
```
public Chronology getChronology()
```
    Description copied from class: ChronoPeriod
    
    Gets the chronology that defines the meaning of the supported units.
    The period is defined by the chronology. It controls the supported units and restricts addition/subtraction to ChronoLocalDate instances of the same chronology.
    
    Specified by:
    
    getChronology in class ChronoPeriod
    
    Returns:
    the chronology defining the period, not null
  - get
```
public long get(TemporalUnit unit)
```
    Description copied from class: ChronoPeriod
    
    Gets the value of the requested unit.
    The supported units are chronology specific. They will typically be YEARS, MONTHS and DAYS. Requesting an unsupported unit will throw an exception.
    
    Specified by:
    
    get in interface TemporalAmount
    
    Specified by:
    
    get in class ChronoPeriod
    
    Parameters:
    unit - the TemporalUnit for which to return the value
    
    Returns:
    the long value of the unit
  - 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.
    
    Overrides:
    
    isZero in class ChronoPeriod
    
    Returns:
    true if this period is zero-length
  - 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.
    
    Overrides:
    
    isNegative in class ChronoPeriod
    
    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 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 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
```
public Period withYears(int years)
```
    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 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
```
public Period withMonths(int months)
```
    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 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
```
public Period withDays(int days)
```
    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
```
public Period plus(TemporalAmount amountToAdd)
```
    Returns a copy of this period with the specified amount added.
    This input amount is converted to a Period using from(TemporalAmount). This operates separately on the years, months and days.
    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".
    This instance is immutable and unaffected by this method call.
    
    Specified by:
    
    plus in class ChronoPeriod
    
    Parameters:
    amountToAdd - the period to add, not null
    
    Returns:
    a Period based on this period with the requested period added, not null
    
    Throws:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - plusYears
```
public Period plusYears(long yearsToAdd)
```
    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:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - plusMonths
```
public Period plusMonths(long monthsToAdd)
```
    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:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - plusDays
```
public Period plusDays(long daysToAdd)
```
    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:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - minus
```
public Period minus(TemporalAmount amountToSubtract)
```
    Returns a copy of this period with the specified amount subtracted.
    This input amount is converted to a Period using from(TemporalAmount). This operates separately on the years, months and days.
    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".
    This instance is immutable and unaffected by this method call.
    
    Specified by:
    
    minus in class ChronoPeriod
    
    Parameters:
    amountToSubtract - the period to subtract, not null
    
    Returns:
    a Period based on this period with the requested period subtracted, not null
    
    Throws:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - minusYears
```
public Period minusYears(long yearsToSubtract)
```
    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:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - minusMonths
```
public Period minusMonths(long monthsToSubtract)
```
    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:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - minusDays
```
public Period minusDays(long daysToSubtract)
```
    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:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - multipliedBy
```
public Period multipliedBy(int scalar)
```
    Returns a new instance with each element in this period multiplied by the specified scalar.
    This simply multiplies each field, years, months, days and normalized time, by the scalar. No normalization is performed.
    
    Specified by:
    
    multipliedBy in class ChronoPeriod
    
    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:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - negated
```
public Period negated()
```
    Returns a new instance with each amount in this period negated.
    
    Overrides:
    
    negated in class ChronoPeriod
    
    Returns:
    a Period based on this period with the amounts negated, not null
    
    Throws:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - normalized
```
public Period normalized()
```
    Returns a copy of this period with the years and months normalized using a 12 month year.
    This normalizes the years and months units, leaving the days unit unchanged. The months unit is adjusted to have an absolute value less than 11, 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 normalization uses a 12 month year which is not valid for all calendar systems.
    This instance is immutable and unaffected by this method call.
    
    Specified by:
    
    normalized in class ChronoPeriod
    
    Returns:
    a Period based on this period with excess months normalized to years, not null
    
    Throws:
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - toTotalMonths
```
public long toTotalMonths()
```
    Gets the total number of months in this period using a 12 month year.
    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 uses a 12 month year which is not valid for all calendar systems.
    This instance is immutable and unaffected by this method call.
    
    Returns:
    the total number of months in the period, may be negative
  - addTo
```
public Temporal addTo(Temporal temporal)
```
    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.
    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 will add the years, then months, then days. Only non-zero amounts will be added. If the date-time has a calendar system with a fixed number of months in a year, then the years and months will be combined before being added.
    This instance is immutable and unaffected by this method call.
    Specified by:
    
    addTo in interface TemporalAmount
    
    Specified by:
    
    addTo in class ChronoPeriod
    
    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 add
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - subtractFrom
```
public Temporal subtractFrom(Temporal temporal)
```
    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.
    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 added if non-zero, otherwise the combination of years and months is added if non-zero. Finally, any days are added. The calculation will subtract the years, then months, then days. Only non-zero amounts will be subtracted. If the date-time has a calendar system with a fixed number of months in a year, then the years and months will be combined before being subtracted.
    This instance is immutable and unaffected by this method call.
    Specified by:
    
    subtractFrom in interface TemporalAmount
    
    Specified by:
    
    subtractFrom in class ChronoPeriod
    
    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 subtract
    
    java.lang.ArithmeticException - if numeric overflow occurs
  - equals
```
public boolean equals(java.lang.Object obj)
```
    Checks if this period is equal to another period.
    The comparison is based on the amounts held in the period. 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 class ChronoPeriod
    
    Parameters:
    obj - the object to check, null returns false
    
    Returns:
    true if this is equal to the other period
  - hashCode
```
public int hashCode()
```
    A hash code for this period.
    
    Specified by:
    
    hashCode in class ChronoPeriod
    
    Returns:
    a suitable hash code
  - toString
```
public java.lang.String toString()
```
    Outputs this period as a String, such as P6Y3M1D.
    The output will be in the ISO-8601 period format. A zero period will be represented as zero days, 'P0D'.
    
    Specified by:
    
    toString in class ChronoPeriod
    
    Returns:
    a string representation of this period, not null

Class Period

Specification for implementors

Field Summary

Method Summary

Methods inherited from class java.time.chrono.ChronoPeriod

Methods inherited from class java.lang.Object

Field Detail

ZERO

Method Detail

ofYears

ofMonths

ofWeeks

ofDays

of

from

between

parse

getUnits

getChronology

get

isZero

isNegative

getYears

getMonths

getDays

withYears

withMonths

withDays

plus

plusYears

plusMonths

plusDays

minus

minusYears

minusMonths

minusDays

multipliedBy

negated

normalized

toTotalMonths

addTo

subtractFrom

equals

hashCode

toString