SerializableZoneOffsetpublic abstract class ZoneId extends Object implements Serializable
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:
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.
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'.
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.
This is a value-based class; use of identity-sensitive operations (including reference equality
(==), identity hash code, or synchronization) on instances of
ZoneId may have unpredictable results and should be avoided.
The equals method should be used for comparisons.
| 限定符和类型 | 字段 | 说明 |
|---|---|---|
static Map<String,String> |
SHORT_IDS |
A map of zone overrides to enable the short time-zone names to be used.
|
| 限定符和类型 | 方法 | 说明 |
|---|---|---|
boolean |
equals(Object obj) |
Checks if this time-zone ID is equal to another time-zone ID.
|
static ZoneId |
from(TemporalAccessor temporal) |
Obtains an instance of
ZoneId from a temporal object. |
static Set<String> |
getAvailableZoneIds() |
Gets the set of available zone IDs.
|
String |
getDisplayName(TextStyle style,
Locale locale) |
Gets the textual representation of the zone, such as 'British Time' or
'+02:00'.
|
abstract String |
getId() |
Gets the unique time-zone ID.
|
abstract ZoneRules |
getRules() |
Gets the time-zone rules for this ID allowing calculations to be performed.
|
int |
hashCode() |
A hash code for this time-zone ID.
|
ZoneId |
normalized() |
Normalizes the time-zone ID, returning a
ZoneOffset where possible. |
static ZoneId |
of(String zoneId) |
Obtains an instance of
ZoneId from an ID ensuring that the
ID is valid and available for use. |
static ZoneId |
of(String zoneId,
Map<String,String> aliasMap) |
Obtains an instance of
ZoneId using its ID using a map
of aliases to supplement the standard zone IDs. |
static ZoneId |
ofOffset(String prefix,
ZoneOffset offset) |
Obtains an instance of
ZoneId wrapping an offset. |
static ZoneId |
systemDefault() |
Gets the system default time-zone.
|
String |
toString() |
Outputs this zone as a
String, using the ID. |
public static final Map<String,String> SHORT_IDS
Use of short zone IDs has been deprecated in java.util.TimeZone.
This map allows the IDs to continue to be used via the
of(java.lang.String,java.util.Map) factory method.
This map contains a mapping of the IDs that is in line with TZDB 2005r and later, where 'EST', 'MST' and 'HST' map to IDs which do not include daylight savings.
This maps as follows:
public static ZoneId systemDefault()
This queries TimeZone#getDefault() to find the default time-zone
and converts it to a ZoneId. If the system default time-zone is changed,
then the result of this method will also change.
DateTimeException - if the converted zone ID has an invalid formatZoneRulesException - if the converted zone region ID cannot be foundpublic static Set<String> getAvailableZoneIds()
This set includes the string form of all available region-based IDs.
Offset-based zone IDs are not included in the returned set.
The ID can be passed to of(java.lang.String) to create a ZoneId.
The set of zone IDs can increase over time, although in a typical application the set of IDs is fixed. Each call to this method is thread-safe.
public static ZoneId of(String zoneId, Map<String,String> aliasMap)
ZoneId using its ID using a map
of aliases to supplement the standard zone IDs.
Many users of time-zones use short abbreviations, such as PST for 'Pacific Standard Time' and PDT for 'Pacific Daylight Time'. These abbreviations are not unique, and so cannot be used as IDs. This method allows a map of string to time-zone to be setup and reused within an application.
zoneId - the time-zone ID, not nullaliasMap - a map of alias zone IDs (typically abbreviations) to real zone IDs, not nullDateTimeException - if the zone ID has an invalid formatZoneRulesException - if the zone ID is a region ID that cannot be foundpublic static ZoneId of(String zoneId)
ZoneId from an ID ensuring that the
ID is valid and available for use.
This method parses the ID producing a ZoneId or ZoneOffset.
A ZoneOffset is returned if the ID is 'Z', or starts with '+' or '-'.
The result will always be a valid ID for which ZoneRules can be obtained.
Parsing matches the zone ID step by step as follows.
ZoneOffset.UTC.
DateTimeException is thrown.
ZoneOffset using ZoneOffset#of(String).
ZoneId
with the same ID and rules equivalent to ZoneOffset.UTC.
ZoneOffset#of(String).
The result will be a ZoneId with the specified UTC/GMT/UT prefix
and the normalized offset ID as per ZoneOffset#getId().
The rules of the returned ZoneId will be equivalent to the
parsed ZoneOffset.
[A-Za-z][A-Za-z0-9~/._+-]+
otherwise a DateTimeException is thrown. If the zone ID is not
in the configured set of IDs, ZoneRulesException is thrown.
The detailed format of the region ID depends on the group supplying the data.
The default set of data is supplied by the IANA Time Zone Database (TZDB).
This has region IDs of the form '{area}/{city}', such as 'Europe/Paris' or 'America/New_York'.
This is compatible with most IDs from TimeZone.
zoneId - the time-zone ID, not nullDateTimeException - if the zone ID has an invalid formatZoneRulesException - if the zone ID is a region ID that cannot be foundpublic static ZoneId ofOffset(String prefix, ZoneOffset offset)
ZoneId wrapping an offset.
If the prefix is "GMT", "UTC", or "UT" a ZoneId
with the prefix and the non-zero offset is returned.
If the prefix is empty "" the ZoneOffset is returned.
prefix - the time-zone ID, not nulloffset - the offset, not nullIllegalArgumentException - if the prefix is not one of
"GMT", "UTC", or "UT", or ""public static ZoneId from(TemporalAccessor temporal)
ZoneId from a temporal object.
This obtains a zone based on the specified temporal.
A TemporalAccessor represents an arbitrary set of date and time information,
which this factory converts to an instance of ZoneId.
A TemporalAccessor represents some form of date and time information.
This factory converts the arbitrary temporal object to an instance of ZoneId.
The conversion will try to obtain the zone in a way that favours region-based
zones over offset-based zones using TemporalQueries#zone().
This method matches the signature of the functional interface TemporalQuery
allowing it to be used as a query via method reference, ZoneId::from.
temporal - the temporal object to convert, not nullDateTimeException - if unable to convert to a ZoneIdpublic abstract String getId()
This ID uniquely defines this object.
The format of an offset based ID is defined by ZoneOffset#getId().
public String getDisplayName(TextStyle style, Locale locale)
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 full ID is returned.
style - the length of the text required, not nulllocale - the locale to use, not nullpublic abstract ZoneRules getRules()
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.
ZoneRulesException - if no rules are available for this IDpublic ZoneId normalized()
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.
public boolean equals(Object obj)
The comparison is based on the ID.
equals 在类中 Objectobj - the object to check, null returns falseObject.hashCode(),
HashMappublic int hashCode()
hashCode 在类中 ObjectObject.equals(java.lang.Object),
System.identityHashCode(java.lang.Object)