TemporalField

A field of date-time, such as month-of-year or hour-of-minute. !(p) Date and time is expressed using fields which partition the time-line into something meaningful for humans. Implementations of this interface represent those fields. !(p) The most commonly used units are defined _in {@link ChronoField}. Further fields are supplied _in {@link IsoFields}, {@link WeekFields} and {@link JulianFields}. Fields can also be written by application code by implementing this interface. !(p) The field works using double dispatch. Client code calls methods on a date-time like {@code LocalDateTime} which check if the field is a {@code ChronoField}. If it is, then the date-time must handle it. Otherwise, the method call is re-dispatched to the matching method _in this interface.

@implSpec 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 be {@code Serializable} where possible. An enum is as effective implementation choice.

@since 1.8

Members

Functions

adjustInto
Temporal adjustInto(Temporal temporal, long newValue)

Returns a copy of the specified temporal object with the value of this field set. !(p) This returns a new temporal object based on the specified one with the value for this field changed. For example, on a {@code 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. !(p) 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. !(p) There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use {@link Temporal#_with(TemporalField, long)}: !(pre) // these two lines are equivalent, but the second approach is recommended temporal = thisField.adjustInto(temporal); temporal = temporal._with(thisField); </pre> It is recommended to use the second approach, {@code _with(TemporalField)}, as it is a lot clearer to read _in code. !(p) Implementations should perform any queries or calculations using the fields available _in {@link ChronoField}. If the field is not supported an {@code UnsupportedTemporalTypeException} must be thrown. !(p) 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.

getBaseUnit
TemporalUnit getBaseUnit()

Gets the unit that the field is measured _in. !(p) 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 {@link #getRangeUnit()}.

getDisplayName
string getDisplayName(Locale locale)

Gets the display name for the field _in the requested locale. !(p) If there is no display name for the locale then a suitable must be returned. !(p) The implementation must check the locale is not null and return {@code toString()}.

getFrom
long getFrom(TemporalAccessor temporal)

Gets the value of this field from the specified temporal object. !(p) This queries the temporal object for the value of this field. !(p) There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use {@link TemporalAccessor#getLong(TemporalField)} (or {@link TemporalAccessor#get(TemporalField)}): !(pre) // these two lines are equivalent, but the second approach is recommended temporal = thisField.getFrom(temporal); temporal = temporal.getLong(thisField); </pre> It is recommended to use the second approach, {@code getLong(TemporalField)}, as it is a lot clearer to read _in code. !(p) Implementations should perform any queries or calculations using the fields available _in {@link ChronoField}. If the field is not supported an {@code UnsupportedTemporalTypeException} must be thrown.

getRangeUnit
TemporalUnit getRangeUnit()

Gets the range that the field is bound by. !(p) 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 {@link #getBaseUnit()}. !(p) 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'.

isDateBased
bool isDateBased()

Checks if this field represents a component of a date. !(p) A field is date-based if it can be derived from {@link ChronoField#EPOCH_DAY EPOCH_DAY}. Note that it is valid for both {@code isDateBased()} and {@code isTimeBased()} to return false, such as when representing a field like minute-of-week.

isSupportedBy
bool isSupportedBy(TemporalAccessor temporal)

Checks if this field is supported by the temporal object. !(p) This determines whether the temporal accessor supports this field. If this returns false, then the temporal cannot be queried for this field. !(p) There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use {@link TemporalAccessor#isSupported(TemporalField)}: !(pre) // these two lines are equivalent, but the second approach is recommended temporal = thisField.isSupportedBy(temporal); temporal = temporal.isSupported(thisField); </pre> It is recommended to use the second approach, {@code isSupported(TemporalField)}, as it is a lot clearer to read _in code. !(p) Implementations should determine whether they are supported using the fields available _in {@link ChronoField}.

isTimeBased
bool isTimeBased()

Checks if this field represents a component of a time. !(p) A field is time-based if it can be derived from {@link ChronoField#NANO_OF_DAY NANO_OF_DAY}. Note that it is valid for both {@code isDateBased()} and {@code isTimeBased()} to return false, such as when representing a field like minute-of-week.

opCmp
int opCmp(TemporalField o)
Undocumented in source.
range
ValueRange range()

Gets the range of valid values for the field. !(p) All fields can be expressed as a {@code 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. !(p) 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.

rangeRefinedBy
ValueRange rangeRefinedBy(TemporalAccessor temporal)

Get the range of valid values for this field using the temporal object to refine the result. !(p) This uses the temporal object to find the range of valid values for the field. This is similar to {@link #range()}, however this method refines the result using the temporal. For example, if the field is {@code DAY_OF_MONTH} the {@code range} 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. !(p) There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use {@link TemporalAccessor#range(TemporalField)}: !(pre) // these two lines are equivalent, but the second approach is recommended temporal = thisField.rangeRefinedBy(temporal); temporal = temporal.range(thisField); </pre> It is recommended to use the second approach, {@code range(TemporalField)}, as it is a lot clearer to read _in code. !(p) Implementations should perform any queries or calculations using the fields available _in {@link ChronoField}. If the field is not supported an {@code UnsupportedTemporalTypeException} must be thrown.

resolve
TemporalAccessor resolve(Map!(TemporalField, Long) fieldValues, TemporalAccessor partialTemporal, ResolverStyle resolverStyle)

Resolves this field to provide a simpler alternative or a date. !(p) This method is invoked during the resolve phase of parsing. It is designed to allow application defined fields to be simplified into more standard fields, such as those on {@code ChronoField}, or into a date. !(p) Applications should not normally invoke this method directly.

toString
string toString()

Gets a descriptive name for the field. !(p) The should be of the format 'BaseOfRange', such as 'MonthOfYear', unless the field has a range of {@code FOREVER}, when only the base unit is mentioned, such as 'Year' or 'Era'.

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