org.threeten.bp

ZoneId

abstract class ZoneId extends Serializable

A time-zone ID, such as Europe/Paris.

A ZoneId is used to identify the rules used to convert between an Instant and a LocalDateTime. There are two distinct types of ID:

Most fixed offsets are represented by ZoneOffset. Calling #normalized() on any ZoneId will ensure that a fixed offset ID will be represented as a ZoneOffset.

The actual rules, describing when and how the offset changes, are defined by ZoneRules. This class is simply an ID used to obtain the underlying rules. This approach is taken because rules are defined by governments and change frequently, whereas the ID is stable.

The distinction has other effects. Serializing the ZoneId will only send the ID, whereas serializing the rules sends the entire data set. Similarly, a comparison of two IDs only examines the ID, whereas a comparison of two rules examines the entire data set.

Time-zone IDs

The ID is unique within the system. There are three types of ID.

The simplest type of ID is that from ZoneOffset. This consists of 'Z' and IDs starting with '+' or '-'.

The next type of ID are offset-style IDs with some form of prefix, such as 'GMT+2' or 'UTC+01:00'. The recognised prefixes are 'UTC', 'GMT' and 'UT'. The offset is the suffix and will be normalized during creation. These IDs can be normalized to a ZoneOffset using normalized().

The third type of ID are region-based IDs. A region-based ID must be of two or more characters, and not start with 'UTC', 'GMT', 'UT' '+' or '-'. Region-based IDs are defined by configuration, see ZoneRulesProvider. The configuration focuses on providing the lookup from the ID to the underlying ZoneRules.

Time-zone rules are defined by governments and change frequently. There are a number of organizations, known here as groups, that monitor time-zone changes and collate them. The default group is the IANA Time Zone Database (TZDB). Other organizations include IATA (the airline industry body) and Microsoft.

Each group defines its own format for the region ID it provides. The TZDB group defines IDs such as 'Europe/London' or 'America/New_York'. TZDB IDs take precedence over other groups.

It is strongly recommended that the group name is included in all IDs supplied by groups other than TZDB to avoid conflicts. For example, IATA airline time-zone region IDs are typically the same as the three letter airport code. However, the airport of Utrecht has the code 'UTC', which is obviously a conflict. The recommended format for region IDs from groups other than TZDB is 'group~region'. Thus if IATA data were defined, Utrecht airport would be 'IATA~UTC'.

Serialization

This class can be serialized and stores the string zone ID in the external form. The ZoneOffset subclass uses a dedicated format that only stores the offset from UTC/Greenwich.

A ZoneId can be deserialized in a Java Runtime where the ID is unknown. For example, if a server-side Java Runtime has been updated with a new zone ID, but the client-side Java Runtime has not been updated. In this case, the ZoneId object will exist, and can be queried using getId, equals, hashCode, toString, getDisplayName and normalized. However, any call to getRules will fail with ZoneRulesException. This approach is designed to allow a ZonedDateTime to be loaded and queried, but not modified, on a Java Runtime with incomplete time-zone information.

Specification for implementors

This abstract class has two implementations, both of which are immutable and thread-safe. One implementation models region-based IDs, the other is ZoneOffset modelling offset-based IDs. This difference is visible in serialization.

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Abstract Value Members

  1. abstract def getId: String

    Gets the unique time-zone ID.

    Gets the unique time-zone ID.

    This ID uniquely defines this object. The format of an offset based ID is defined by ZoneOffset#getId().

    returns

    the time-zone unique ID, not null

  2. abstract def getRules: ZoneRules

    Gets the time-zone rules for this ID allowing calculations to be performed.

    Gets the time-zone rules for this ID allowing calculations to be performed.

    The rules provide the functionality associated with a time-zone, such as finding the offset for a given instant or local date-time.

    A time-zone can be invalid if it is deserialized in a Java Runtime which does not have the same rules loaded as the Java Runtime that stored it. In this case, calling this method will throw a ZoneRulesException.

    The rules are supplied by ZoneRulesProvider. An advanced provider may support dynamic updates to the rules without restarting the Java Runtime. If so, then the result of this method may change over time. Each individual call will be still remain thread-safe.

    ZoneOffset will always return a set of rules where the offset never changes.

    returns

    the rules, not null

    Exceptions thrown
    ZoneRulesException

    if no rules are available for this ID

Concrete Value Members

  1. final def !=(arg0: AnyRef): Boolean

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  2. final def !=(arg0: Any): Boolean

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  3. final def ##(): Int

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  4. final def ==(arg0: AnyRef): Boolean

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  5. final def ==(arg0: Any): Boolean

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  6. final def asInstanceOf[T0]: T0

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  7. def clone(): AnyRef

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    @throws( ... )
  8. final def eq(arg0: AnyRef): Boolean

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  9. def equals(obj: Any): Boolean

    Checks if this time-zone ID is equal to another time-zone ID.

    Checks if this time-zone ID is equal to another time-zone ID.

    The comparison is based on the ID.

    obj

    the object to check, null returns false

    returns

    true if this is equal to the other time-zone ID

    Definition Classes
    ZoneId → AnyRef → Any
  10. def finalize(): Unit

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  11. final def getClass(): Class[_]

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  12. def getDisplayName(style: TextStyle, locale: Locale): String

    Gets the textual representation of the zone, such as 'British Time' or '+02:00'.

    Gets the textual representation of the zone, such as 'British Time' or '+02:00'.

    This returns the textual name used to identify the time-zone ID, suitable for presentation to the user. The parameters control the style of the returned text and the locale.

    If no textual mapping is found then the #getId() full ID is returned.

    style

    the length of the text required, not null

    locale

    the locale to use, not null

    returns

    the text value of the zone, not null

  13. def hashCode(): Int

    A hash code for this time-zone ID.

    A hash code for this time-zone ID.

    returns

    a suitable hash code

    Definition Classes
    ZoneId → AnyRef → Any
  14. final def isInstanceOf[T0]: Boolean

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  15. final def ne(arg0: AnyRef): Boolean

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  16. def normalized: ZoneId

    Normalizes the time-zone ID, returning a ZoneOffset where possible.

    Normalizes the time-zone ID, returning a ZoneOffset where possible.

    The returns a normalized ZoneId that can be used in place of this ID. The result will have ZoneRules equivalent to those returned by this object, however the ID returned by getId() may be different.

    The normalization checks if the rules of this ZoneId have a fixed offset. If they do, then the ZoneOffset equal to that offset is returned. Otherwise this is returned.

    returns

    the time-zone unique ID, not null

  17. final def notify(): Unit

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  18. final def notifyAll(): Unit

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  19. final def synchronized[T0](arg0: ⇒ T0): T0

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  20. def toString(): String

    Outputs this zone as a String, using the ID.

    Outputs this zone as a String, using the ID.

    returns

    a string representation of this time-zone ID, not null

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    ZoneId → AnyRef → Any
  21. final def wait(): Unit

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  22. final def wait(arg0: Long, arg1: Int): Unit

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  23. final def wait(arg0: Long): Unit

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