Interface TemporalField
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- All Known Implementing Classes:
ChronoField
public interface TemporalField
A field of date-time, such as month-of-year or hour-of-minute.Date and time is expressed using fields which partition the time-line into something meaningful for humans. Implementations of this interface represent those fields.
The most commonly used units are defined in
ChronoField
. Further fields are supplied inIsoFields
,WeekFields
andJulianFields
. Fields can also be written by application code by implementing this interface.The field works using double dispatch. Client code calls methods on a date-time like
LocalDateTime
which check if the field is aChronoField
. If it is, then the date-time must handle it. Otherwise, the method call is re-dispatched to the matching method in this interface.Specification for implementors
This interface must be implemented with care to ensure other classes operate correctly. All implementations that can be instantiated must be final, immutable and thread-safe. Implementations should beSerializable
where possible. An enum is as effective implementation choice.
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description <R extends Temporal>
RadjustInto(R temporal, long newValue)
Returns a copy of the specified temporal object with the value of this field set.TemporalUnit
getBaseUnit()
Gets the unit that the field is measured in.String
getDisplayName(Locale locale)
Gets the display name for the field in the requested locale.long
getFrom(TemporalAccessor temporal)
Gets the value of this field from the specified temporal object.TemporalUnit
getRangeUnit()
Gets the range that the field is bound by.boolean
isDateBased()
Checks if this field is date-based.boolean
isSupportedBy(TemporalAccessor temporal)
Checks if this field is supported by the temporal object.boolean
isTimeBased()
Checks if this field is time-based.ValueRange
range()
Gets the range of valid values for the field.ValueRange
rangeRefinedBy(TemporalAccessor temporal)
Get the range of valid values for this field using the temporal object to refine the result.TemporalAccessor
resolve(Map<TemporalField,Long> fieldValues, TemporalAccessor partialTemporal, ResolverStyle resolverStyle)
Resolves the date/time information in the builder
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Method Detail
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getBaseUnit
TemporalUnit getBaseUnit()
Gets the unit that the field is measured in.The unit of the field is the period that varies within the range. For example, in the field 'MonthOfYear', the unit is 'Months'. See also
getRangeUnit()
.- Returns:
- the period unit defining the base unit of the field, not null
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getRangeUnit
TemporalUnit getRangeUnit()
Gets the range that the field is bound by.The range of the field is the period that the field varies within. For example, in the field 'MonthOfYear', the range is 'Years'. See also
getBaseUnit()
.The range is never null. For example, the 'Year' field is shorthand for 'YearOfForever'. It therefore has a unit of 'Years' and a range of 'Forever'.
- Returns:
- the period unit defining the range of the field, not null
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range
ValueRange range()
Gets the range of valid values for the field.All fields can be expressed as a
long
integer. This method returns an object that describes the valid range for that value. This method is generally only applicable to the ISO-8601 calendar system.Note that the result only describes the minimum and maximum valid values and it is important not to read too much into them. For example, there could be values within the range that are invalid for the field.
- Returns:
- the range of valid values for the field, not null
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isDateBased
boolean isDateBased()
Checks if this field is date-based.A date-based field can be derived from epoch-day
- Returns:
- true if date-based
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isTimeBased
boolean isTimeBased()
Checks if this field is time-based.A time-based field can be derived from nano-of-day
- Returns:
- true if time-based
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isSupportedBy
boolean isSupportedBy(TemporalAccessor temporal)
Checks if this field is supported by the temporal object.This determines whether the temporal accessor supports this field. If this returns false, the temporal cannot be queried for this field.
There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use
TemporalAccessor.isSupported(TemporalField)
:// these two lines are equivalent, but the second approach is recommended temporal = thisField.isSupportedBy(temporal); temporal = temporal.isSupported(thisField);
It is recommended to use the second approach,isSupported(TemporalField)
, as it is a lot clearer to read in code.Implementations should determine whether they are supported using the fields available in
ChronoField
.- Parameters:
temporal
- the temporal object to query, not null- Returns:
- true if the date-time can be queried for this field, false if not
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rangeRefinedBy
ValueRange rangeRefinedBy(TemporalAccessor temporal)
Get the range of valid values for this field using the temporal object to refine the result.This uses the temporal object to find the range of valid values for the field. This is similar to
range()
, however this method refines the result using the temporal. For example, if the field isDAY_OF_MONTH
therange
method is not accurate as there are four possible month lengths, 28, 29, 30 and 31 days. Using this method with a date allows the range to be accurate, returning just one of those four options.There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use
TemporalAccessor.range(TemporalField)
:// these two lines are equivalent, but the second approach is recommended temporal = thisField.rangeRefinedBy(temporal); temporal = temporal.range(thisField);
It is recommended to use the second approach,range(TemporalField)
, as it is a lot clearer to read in code.Implementations should perform any queries or calculations using the fields available in
ChronoField
. If the field is not supported aDateTimeException
must be thrown.- Parameters:
temporal
- the temporal object used to refine the result, not null- Returns:
- the range of valid values for this field, not null
- Throws:
DateTimeException
- if the range for the field cannot be obtained
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getFrom
long getFrom(TemporalAccessor temporal)
Gets the value of this field from the specified temporal object.This queries the temporal object for the value of this field.
There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use
TemporalAccessor.getLong(TemporalField)
(orTemporalAccessor.get(TemporalField)
):// these two lines are equivalent, but the second approach is recommended temporal = thisField.getFrom(temporal); temporal = temporal.getLong(thisField);
It is recommended to use the second approach,getLong(TemporalField)
, as it is a lot clearer to read in code.Implementations should perform any queries or calculations using the fields available in
ChronoField
. If the field is not supported aDateTimeException
must be thrown.- Parameters:
temporal
- the temporal object to query, not null- Returns:
- the value of this field, not null
- Throws:
DateTimeException
- if a value for the field cannot be obtained
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getDisplayName
String getDisplayName(Locale locale)
Gets the display name for the field in the requested locale.If there is no display name for the locale then a suitable default must be returned.
The default implementation must check the locale is not null and return
toString()
.- Parameters:
locale
- the locale to use, not null- Returns:
- the display name for the locale or a suitable default, not null
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adjustInto
<R extends Temporal> R adjustInto(R temporal, long newValue)
Returns a copy of the specified temporal object with the value of this field set.This returns a new temporal object based on the specified one with the value for this field changed. For example, on a
LocalDate
, this could be used to set the year, month or day-of-month. The returned object has the same observable type as the specified object.In some cases, changing a field is not fully defined. For example, if the target object is a date representing the 31st January, then changing the month to February would be unclear. In cases like this, the implementation is responsible for resolving the result. Typically it will choose the previous valid date, which would be the last valid day of February in this example.
There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use
Temporal.with(TemporalField, long)
:// these two lines are equivalent, but the second approach is recommended temporal = thisField.adjustInto(temporal); temporal = temporal.with(thisField);
It is recommended to use the second approach,with(TemporalField)
, as it is a lot clearer to read in code.Implementations should perform any queries or calculations using the fields available in
ChronoField
. If the field is not supported aDateTimeException
must be thrown.Implementations must not alter the specified temporal object. Instead, an adjusted copy of the original must be returned. This provides equivalent, safe behavior for immutable and mutable implementations.
- Type Parameters:
R
- the type of the Temporal object- Parameters:
temporal
- the temporal object to adjust, not nullnewValue
- the new value of the field- Returns:
- the adjusted temporal object, not null
- Throws:
DateTimeException
- if the field cannot be set
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resolve
TemporalAccessor resolve(Map<TemporalField,Long> fieldValues, TemporalAccessor partialTemporal, ResolverStyle resolverStyle)
Resolves the date/time information in the builderThis method is invoked during the resolve of the builder. Implementations should combine the associated field with others to form objects like
LocalDate
,LocalTime
andLocalDateTime
- Parameters:
fieldValues
- the map of fields to values, which can be updated, not nullpartialTemporal
- the partially complete temporal to query for zone and chronology; querying for other things is undefined and not recommended, not nullresolverStyle
- the requested type of resolve, not null- Returns:
- the resolved temporal object; null if resolving only changed the map, or no resolve occurred
- Throws:
ArithmeticException
- if numeric overflow occursDateTimeException
- if resolving results in an error. This must not be thrown by querying a field on the temporal without first checking if it is supported
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