Gets the value of the specified field as a long.

This queries the date-time for the value for the specified field. The returned value may be outside the valid range of values for the field. If the date-time cannot return the value, because the field is unsupported or for some other reason, an exception will be thrown.

Specification for implementors

Implementations must check and handle all fields defined in ChronoField. If the field is supported, then the value of the field must be returned. If unsupported, then a DateTimeException must be thrown.

If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.getFrom(TemporalAccessor) passing this as the argument.

Implementations must not alter either this object.

Checks if the specified unit is supported.

This checks if the date-time can be queried for the specified unit. If false, then calling the plus and minus methods will throw an exception.

Specification for implementors

Implementations must check and handle all fields defined in ChronoUnit. If the field is supported, then true is returned, otherwise false

If the field is not a ChronoUnit, then the result of this method is obtained by invoking TemporalUnit.isSupportedBy(Temporal) passing this as the argument.

Implementations must not alter this object.

Checks if the specified field is supported.

This checks if the date-time can be queried for the specified field. If false, then calling the range and get methods will throw an exception.

Specification for implementors

Implementations must check and handle all fields defined in ChronoField. If the field is supported, then true is returned, otherwise false

If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.isSupportedBy(TemporalAccessor) passing this as the argument.

Implementations must not alter this object.

Returns an object of the same type as this object with the specified period added.

This method returns a new object based on this one with the specified period added. For example, on a LocalDate, this could be used to add a number of years, months or days. The returned object will have the same observable type as this 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 adding one month would be unclear. In cases like this, the field 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.

If the implementation represents a date-time that has boundaries, such as LocalTime, then the permitted units must include the boundary unit, but no multiples of the boundary unit. For example, LocalTime must accept DAYS but not WEEKS or MONTHS.

Specification for implementors

Implementations must check and handle all units defined in ChronoUnit. If the unit is supported, then the addition must be performed. If unsupported, then a DateTimeException must be thrown.

If the unit is not a ChronoUnit, then the result of this method is obtained by invoking TemporalUnit.addTo(Temporal, long) passing this as the first argument.

Implementations must not alter either this object or the specified temporal object. Instead, an adjusted copy of the original must be returned. This provides equivalent, safe behavior for immutable and mutable implementations.

Calculates the period between this temporal and another temporal in terms of the specified unit.

This calculates the period between two temporals in terms of a single unit. The start and end points are this and the specified temporal. The result will be negative if the end is before the start. For example, the period in hours between two temporal objects can be calculated using startTime.until(endTime, HOURS).

The calculation returns a whole number, representing the number of complete units between the two temporals. For example, the period in hours between the times 11:30 and 13:29 will only be one hour as it is one minute short of two hours.

There are two equivalent ways of using this method. The first is to invoke this method directly. The second is to use Temporal):

 // these
two lines are equivalent between = thisUnit.between(start, end); between = start.until(end,
thisUnit); 

For example, this method allows the number of days between two dates to be calculated:

val daysBetween: Long = DAYS.between(start, end); // or alternatively val daysBetween: Long =
start.until(end, DAYS); 

Specification for implementors

Implementations must begin by checking to ensure that the input temporal object is of the same observable type as the implementation. They must then perform the calculation for all instances of ChronoUnit. A DateTimeException must be thrown for ChronoUnit instances that are unsupported.

If the unit is not a ChronoUnit, then the result of this method is obtained by invoking TemporalUnit.between(Temporal, Temporal) passing this as the first argument and the input temporal as the second argument.

In summary, implementations must behave in a manner equivalent to this code:

 // check
input temporal is the same type as this class if (unit instanceof ChronoUnit) { // if unit is
supported, then calculate and return result // else throw DateTimeException for unsupported
units } return unit.between(this, endTemporal); 

The target object must not be altered by this method.

thisUnit);

For example, this method allows the number of days between two dates to be calculated:

val daysBetween: Long = DAYS.between(start, end); // or alternatively val daysBetween: Long =
start.until(end, DAYS); 

Specification for implementors

Implementations must begin by checking to ensure that the input temporal object is of the same observable type as the implementation. They must then perform the calculation for all instances of ChronoUnit. A DateTimeException must be thrown for ChronoUnit instances that are unsupported.

If the unit is not a ChronoUnit, then the result of this method is obtained by invoking TemporalUnit.between(Temporal, Temporal) passing this as the first argument and the input temporal as the second argument.

In summary, implementations must behave in a manner equivalent to this code:

 // check
input temporal is the same type as this class if (unit instanceof ChronoUnit) { // if unit is
supported, then calculate and return result // else throw DateTimeException for unsupported
units } return unit.between(this, endTemporal); 

The target object must not be altered by this method.

Returns an object of the same type as this object with the specified field altered.

This returns a new object based on this one with the value for the specified field changed. For example, on a LocalDate, this could be used to set the year, month or day-of-month. The returned object will have the same observable type as this 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 field 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.

Specification for implementors

Implementations must check and handle all fields defined in ChronoField. If the field is supported, then the adjustment must be performed. If unsupported, then a DateTimeException must be thrown.

If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.adjustInto(Temporal, long) passing this as the first argument.

Implementations must not alter either this object or the specified temporal object. Instead, an adjusted copy of the original must be returned. This provides equivalent, safe behavior for immutable and mutable implementations.

Gets the value of the specified field as an int.

This queries the date-time for the value for the specified field. The returned value will always be within the valid range of values for the field. If the date-time cannot return the value, because the field is unsupported or for some other reason, an exception will be thrown.

Specification for implementors

Implementations must check and handle all fields defined in ChronoField. If the field is supported and has an int range, then the value of the field must be returned. If unsupported, then a DateTimeException must be thrown.

If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.getFrom(TemporalAccessor) passing this as the argument.

Implementations must not alter either this object.

Returns an object of the same type as this object with the specified period subtracted.

This method returns a new object based on this one with the specified period subtracted. For example, on a LocalDate, this could be used to subtract a number of years, months or days. The returned object will have the same observable type as this object.

In some cases, changing a field is not fully defined. For example, if the target object is a date representing the 31st March, then subtracting one month would be unclear. In cases like this, the field 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.

If the implementation represents a date-time that has boundaries, such as LocalTime, then the permitted units must include the boundary unit, but no multiples of the boundary unit. For example, LocalTime must accept DAYS but not WEEKS or MONTHS.

Specification for implementors

Implementations must behave in a manor equivalent to the default method behavior.

Implementations must not alter either this object or the specified temporal object. Instead, an adjusted copy of the original must be returned. This provides equivalent, safe behavior for immutable and mutable implementations.

Returns an object of the same type as this object with an amount subtracted.

This adjusts this temporal, subtracting according to the rules of the specified amount. The amount is typically a Period but may be any other type implementing the TemporalAmount interface, such as Duration.

Some example code indicating how and why this method is used:

 date = date.minus(period);
// subtract a Period instance date = date.minus(duration); // subtract a Duration instance date
\= date.minus(workingDays(6)); // example user-written workingDays method 

Note that calling plus followed by minus is not guaranteed to return the same date-time.

Specification for implementors

Implementations must not alter either this object. Instead, an adjusted copy of the original must be returned. This provides equivalent, safe behavior for immutable and mutable implementations.

Returns an object of the same type as this object with an amount added.

This adjusts this temporal, adding according to the rules of the specified amount. The amount is typically a Period but may be any other type implementing the TemporalAmount interface, such as Duration.

Some example code indicating how and why this method is used:

 date = date.plus(period);
// add a Period instance date = date.plus(duration); // add a Duration instance date =
date.plus(workingDays(6)); // example user-written workingDays method 

Note that calling plus followed by minus is not guaranteed to return the same date-time.

Specification for implementors

Implementations must not alter either this object. Instead, an adjusted copy of the original must be returned. This provides equivalent, safe behavior for immutable and mutable implementations.

Queries this date-time.

This queries this date-time using the specified query strategy object.

Queries are a key tool for extracting information from date-times. They exists to externalize the process of querying, permitting different approaches, as per the strategy design pattern. Examples might be a query that checks if the date is the day before February 29th in a leap year, or calculates the number of days to your next birthday.

The most common query implementations are method references, such as LocalDate::from and ZoneId::from. Further implementations are on TemporalQueries. Queries may also be defined by applications.

Specification for implementors

Implementations of this method must behave as follows:

 public <R> R query(TemporalQuery<R> type) { // only include an if statement
if the implementation can return it if (query == TemporalQueries.zoneId()) return // the ZoneId
if (query == TemporalQueries.chronology()) return // the Chrono if (query ==
TemporalQueries.precision()) return // the precision // call default method return
super.query(query); } 

Gets the range of valid values for the specified field.

All fields can be expressed as a long integer. This method returns an object that describes the valid range for that value. The value of this temporal object is used to enhance the accuracy of the returned range. If the date-time cannot return the range, because the field is unsupported or for some other reason, an exception will be thrown.

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.

Specification for implementors

Implementations must check and handle all fields defined in ChronoField. If the field is supported, then the range of the field must be returned. If unsupported, then a DateTimeException must be thrown.

If the field is not a ChronoField, then the result of this method is obtained by invoking TemporalField.rangeRefinedBy(TemporalAccessorl) passing this as the argument.

Implementations must not alter either this object.

Returns an adjusted object of the same type as this object with the adjustment made.

This adjusts this date-time according to the rules of the specified adjuster. A simple adjuster might simply set the one of the fields, such as the year field. A more complex adjuster might set the date to the last day of the month. A selection of common adjustments is provided in TemporalAdjusters. These include finding the "last day of the month" and "next Wednesday". The adjuster is responsible for handling special cases, such as the varying lengths of month and leap years.

Some example code indicating how and why this method is used:

 date =
date.with(Month.JULY); // most key classes implement TemporalAdjuster date =
date.with(lastDayOfMonth()); // static import from TemporalAdjusters date =
date.with(next(WEDNESDAY)); // static import from TemporalAdjusters and DayOfWeek 

Specification for implementors

Implementations must not alter either this object. Instead, an adjusted copy of the original must be returned. This provides equivalent, safe behavior for immutable and mutable implementations.