Queries (ThreeTen Date and Time API)

java.lang.Object
- java.time.temporal.Queries

```
public final class Queries
extends java.lang.Object
```
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(TemporalAccessor) 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(TemporalQuery):
```
   // 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(TemporalQuery), as it is a lot clearer to read in code.
Specification for implementors
This is a thread-safe utility class. All returned adjusters are immutable and thread-safe.
Since:

1.8

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method and Description
`static TemporalQuery<Chrono<?>>`	`chrono()` A query for the `Chrono`.
`static TemporalQuery<ZoneOffset>`	`offset()` A query for the `ZoneOffset`.
`static TemporalQuery<ChronoUnit>`	`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`.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Method Detail
  - zoneId
```
public static final 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
    OffsetDate returns null
    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
    
    Returns:
    a ZoneId, may be null
  - chrono
```
public static final TemporalQuery<Chrono<?>> chrono()
```
    A query for the Chrono.
    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 ISOChrono.INSTANCE
    LocalTime returns null (does not represent a date)
    LocalDateTime returns ISOChrono.INSTANCE
    ZonedDateTime returns ISOChrono.INSTANCE
    OffsetDate returns ISOChrono.INSTANCE
    OffsetTime returns null (does not represent a date)
    OffsetDateTime returns ISOChrono.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 ISOChrono.INSTANCE
    Year returns ISOChrono.INSTANCE
    YearMonth returns ISOChrono.INSTANCE
    MonthDay returns null ISOChrono.INSTANCE
    ZoneOffset returns null (does not represent a date)
    Instant returns null (does not represent a date)
    
    The method Chrono.from(TemporalAccessor) can be used as a TemporalQuery via a method reference, Chrono::from. That method is equivalent to this query, except that it throws an exception if a chronology cannot be obtained.
    
    Returns:
    a Chrono, may be null
  - precision
```
public static final TemporalQuery<ChronoUnit> 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
    OffsetDate returns DAYS
    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
    
    Returns:
    a ChronoUnit, may be null
  - zone
```
public static final 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().
    In most cases, applications should use this query rather than #zoneId().
    This query examines the offset-seconds field and uses it to create a ZoneOffset.
    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.
    
    Returns:
    a ZoneId, may be null
  - offset
```
public static final TemporalQuery<ZoneOffset> offset()
```
    A query for the ZoneOffset.
    This queries a TemporalAccessor for the offset.
    This query examines the 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. That method is equivalent to this query, except that it throws an exception if an offset cannot be obtained.
    
    Returns:
    a ZoneOffset, may be null

Class Queries

Specification for implementors

Method Summary

Methods inherited from class java.lang.Object

Method Detail

zoneId

chrono

precision

zone

offset