Home Reference Source
import {TemporalQueries} from 'js-joda/src/temporal/TemporalQueries.js'
public class | source

TemporalQueries

Common implementations of TemporalQuery.

This class provides common implementations of TemporalQuery. These queries are primarily used as optimizations, allowing the internals of other objects to be extracted effectively. Note that application code can also use the from method on most temporal objects as a method reference matching the query interface, such as LocalDate::from and ZoneId::from.

There are two equivalent ways of using a TemporalQuery. The first is to invoke the method on the interface directly. The second is to use TemporalAccessor#query:

  // these two lines are equivalent, but the second approach is recommended
  dateTime = query.queryFrom(dateTime);
  dateTime = dateTime.query(query);
It is recommended to use the second approach, query, as it is a lot clearer to read in code.

Static Method Summary

Static Public Methods
public static

A query for the Chronology.

public static

localDate(): *

A query for LocalDate returning null if not found.

public static

localTime(): *

A query for LocalTime returning null if not found.

public static

offset(): *

A query for ZoneOffset returning null if not found.

public static

precision(): *

A query for the smallest supported unit.

public static

zone(): *

A lenient query for the ZoneId, falling back to the ZoneOffset.

public static

zoneId(): *

A strict query for the ZoneId.

Static Public Methods

public static chronology(): TemporalQuery source

A query for the Chronology.

This queries a TemporalAccessor for the chronology. If the target TemporalAccessor represents a date, or part of a date, then it should return the chronology that the date is expressed in. As a result of this definition, objects only representing time, such as LocalTime, will return null.

The result from js-joda classes implementing TemporalAccessor is as follows:

  • LocalDate returns * IsoChronology.INSTANCE
  • LocalTime returns null (does not represent a date)
  • LocalDateTime returns * IsoChronology.INSTANCE
  • ZonedDateTime returns * IsoChronology.INSTANCE
  • OffsetTime returns null (does not represent a date)
  • OffsetDateTime returns * IsoChronology.INSTANCE
  • ChronoLocalDate returns the associated chronology
  • ChronoLocalDateTime returns the associated chronology
  • ChronoZonedDateTime returns the associated chronology
  • Era returns the associated chronology
  • DayOfWeek returns null (shared across chronologies)
  • Month returns * IsoChronology.INSTANCE
  • Year returns * IsoChronology.INSTANCE
  • YearMonth returns * IsoChronology.INSTANCE
  • MonthDay returns null * IsoChronology.INSTANCE
  • ZoneOffset returns null (does not represent a date)
  • Instant returns null (does not represent a date)

The method Chronology#from can be used as a TemporalQuery That method is equivalent to this query, except that it throws an exception if a chronology cannot be obtained.

Return:

TemporalQuery

a query that can obtain the chronology of a temporal, not null

public static localDate(): * source

A query for LocalDate returning null if not found.

This returns a TemporalQuery that can be used to query a temporal object for the local date. The query will return null if the temporal object cannot supply a local date.

The query implementation examines the ChronoField#EPOCH_DAY field and uses it to create a LocalDate.

Return:

*

a query that can obtain the date of a temporal, not null

public static localTime(): * source

A query for LocalTime returning null if not found.

This returns a TemporalQuery that can be used to query a temporal object for the local time. The query will return null if the temporal object cannot supply a local time.

The query implementation examines the ChronoField#NANO_OF_DAY field and uses it to create a LocalTime.

Return:

*

a query that can obtain the time of a temporal, not null

public static offset(): * source

A query for ZoneOffset returning null if not found.

This returns a TemporalQuery that can be used to query a temporal object for the offset. The query will return null if the temporal object cannot supply an offset.

The query implementation examines the ChronoField#OFFSET_SECONDS field and uses it to create a ZoneOffset.

The method java.time.ZoneOffset#from can be used as a TemporalQuery via a method reference, ZoneOffset::from. This query and ZoneOffset::from will return the same result if the temporal object contains an offset. If the temporal object does not contain an offset, then the method reference will throw an exception, whereas this query will return null.

Return:

*

a query that can obtain the offset of a temporal, not null

public static precision(): * source

A query for the smallest supported unit.

This queries a TemporalAccessor for the time precision. If the target TemporalAccessor represents a consistent or complete date-time, date or time then this must return the smallest precision actually supported. Note that fields such as NANO_OF_DAY and NANO_OF_SECOND are defined to always return ignoring the precision, thus this is the only way to find the actual smallest supported unit. For example, were GregorianCalendar to implement TemporalAccessor it would return a precision of MILLIS.

The result from js-joda classes implementing TemporalAccessor is as follows:

LocalDate returns DAYS LocalTime returns NANOS LocalDateTime returns NANOS ZonedDateTime returns NANOS OffsetTime returns NANOS OffsetDateTime returns NANOS ChronoLocalDate returns DAYS ChronoLocalDateTime returns NANOS ChronoZonedDateTime returns NANOS Era returns ERAS DayOfWeek returns DAYS Month returns MONTHS Year returns YEARS YearMonth returns MONTHS MonthDay returns null (does not represent a complete date or time) ZoneOffset returns null (does not represent a date or time) Instant returns NANOS

Return:

*

a query that can obtain the precision of a temporal, not null

public static zone(): * source

A lenient query for the ZoneId, falling back to the ZoneOffset.

This queries a TemporalAccessor for the zone. It first tries to obtain the zone, using zoneId. If that is not found it tries to obtain the offset.

In most cases, applications should use this query rather than zoneId.

This query examines the ChronoField#OFFSET_SECONDS field and uses it to create a ZoneOffset.

The method ZoneId#from can be used as a TemporalQuery via a method reference, ZoneId::from. That method is equivalent to this query, except that it throws an exception if a zone cannot be obtained.

Return:

*

a query that can obtain the zone ID or offset of a temporal, not null

public static zoneId(): * source

A strict query for the ZoneId.

This queries a TemporalAccessor for the zone. The zone is only returned if the date-time conceptually contains a ZoneId. It will not be returned if the date-time only conceptually has an ZoneOffset. Thus a ZonedDateTime will return the result of getZone, but an OffsetDateTime will return null.

In most cases, applications should use ZONE as this query is too strict.

The result from JDK classes implementing TemporalAccessor is as follows:

Return:

*

a query that can obtain the zone ID of a temporal, not null