TemporalQueries

java.lang.Object
- java.time.temporal.TemporalQueries

```
public final class TemporalQueries
extends Object
```
Common implementations of TemporalQuery.
This class provides common implementations of TemporalQuery. These are defined here as they must be constants, and the definition of lambdas does not guarantee that. By assigning them once here, they become 'normal' Java constants.
Queries are a key tool for extracting information from temporal objects. They exist 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 TemporalField interface provides another mechanism for querying temporal objects. That interface is limited to returning a long. By contrast, queries can return any type.
There are two equivalent ways of using a TemporalQuery. The first is to invoke the method on this interface directly. The second is to use TemporalAccessor#query(TemporalQuery):
```
   // these two lines are equivalent, but the second approach is recommended
   temporal = thisQuery.queryFrom(temporal);
   temporal = temporal.query(thisQuery);
 
```
It is recommended to use the second approach, query(TemporalQuery), as it is a lot clearer to read in code.
The most common implementations are method references, such as LocalDate::from and ZoneId::from. Additional common queries are provided to return:
- a Chronology,
- a LocalDate,
- a LocalTime,
- a ZoneOffset,
- a precision,
- a zone, or
- a zoneId.
从以下版本开始:

1.8

方法概要

所有方法静态方法具体方法
限定符和类型	方法	说明
`static TemporalQuery<Chronology>`	`chronology()`	A query for the `Chronology`.
`static TemporalQuery<LocalDate>`	`localDate()`	A query for `LocalDate` returning null if not found.
`static TemporalQuery<LocalTime>`	`localTime()`	A query for `LocalTime` returning null if not found.
`static TemporalQuery<ZoneOffset>`	`offset()`	A query for `ZoneOffset` returning null if not found.
`static TemporalQuery<TemporalUnit>`	`precision()`	A query for the smallest supported unit.
`static TemporalQuery<ZoneId>`	`zone()`	A lenient query for the `ZoneId`, falling back to the `ZoneOffset`.
`static TemporalQuery<ZoneId>`	`zoneId()`	A strict query for the `ZoneId`.

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- 方法详细资料
  - zoneId
```
public static TemporalQuery<ZoneId> zoneId()
```
    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:
    LocalDate returns null
    LocalTime returns null
    LocalDateTime returns null
    ZonedDateTime returns the associated zone
    OffsetTime returns null
    OffsetDateTime returns null
    ChronoLocalDate returns null
    ChronoLocalDateTime returns null
    ChronoZonedDateTime returns the associated zone
    Era returns null
    DayOfWeek returns null
    Month returns null
    Year returns null
    YearMonth returns null
    MonthDay returns null
    ZoneOffset returns null
    Instant returns null
    
    返回:
    
    a query that can obtain the zone ID of a temporal, not null
  - chronology
```
public static TemporalQuery<Chronology> chronology()
```
    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 JDK 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(TemporalAccessor) can be used as a TemporalQuery via a method reference, Chronology::from. That method is equivalent to this query, except that it throws an exception if a chronology cannot be obtained.
    
    返回:
    
    a query that can obtain the chronology of a temporal, not null
  - precision
```
public static TemporalQuery<TemporalUnit> precision()
```
    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 JDK 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
    
    返回:
    
    a query that can obtain the precision of a temporal, not null
  - zone
```
public static TemporalQuery<ZoneId> zone()
```
    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(). Thus a ZonedDateTime will return the result of getZone(), while an OffsetDateTime will return the result of getOffset().
    In most cases, applications should use this query rather than #zoneId().
    The method ZoneId#from(TemporalAccessor) 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.
    
    返回:
    
    a query that can obtain the zone ID or offset of a temporal, not null
  - offset
```
public static TemporalQuery<ZoneOffset> offset()
```
    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 ZoneOffset.from(TemporalAccessor) 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.
    
    返回:
    
    a query that can obtain the offset of a temporal, not null
  - localDate
```
public static TemporalQuery<LocalDate> localDate()
```
    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.
    The method ZoneOffset#from(TemporalAccessor) can be used as a TemporalQuery via a method reference, LocalDate::from. This query and LocalDate::from will return the same result if the temporal object contains a date. If the temporal object does not contain a date, then the method reference will throw an exception, whereas this query will return null.
    
    返回:
    
    a query that can obtain the date of a temporal, not null
  - localTime
```
public static TemporalQuery<LocalTime> localTime()
```
    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.
    The method ZoneOffset#from(TemporalAccessor) can be used as a TemporalQuery via a method reference, LocalTime::from. This query and LocalTime::from will return the same result if the temporal object contains a time. If the temporal object does not contain a time, then the method reference will throw an exception, whereas this query will return null.
    
    返回:
    
    a query that can obtain the time of a temporal, not null

类 TemporalQueries

方法概要

从类继承的方法 java.lang.Object

方法详细资料

zoneId

chronology

precision

zone

offset

localDate

localTime