org.threeten.bp

Class ZoneId

java.lang.Object

org.threeten.bp.ZoneId

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

ZoneOffset

public abstract class ZoneId
extends Object
implements 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:

• Fixed offsets - a fully resolved offset from UTC/Greenwich, that uses the same offset for all local date-times
• Geographical regions - an area where a specific set of rules for finding the offset from UTC/Greenwich apply

Most fixed offsets are represented by 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 code supports loading a ZoneId on a JVM which does not have available rules for that ID. This allows the date-time object, such as ZonedDateTime, to still be queried.

Time-zone IDs

The ID is unique within the system. The formats for offset and region IDs differ.

An ID is parsed as an offset ID if it starts with 'UTC', 'GMT', '+' or '-', or is a single letter. For example, 'Z', '+02:00', '-05:00', 'UTC+05' and 'GMT-6' are all valid offset IDs. Note that some IDs, such as 'D' or '+ABC' meet the criteria, but are invalid.

All other IDs are considered to be region IDs.

Region IDs are defined by configuration, which can be thought of as a Map from region ID to ZoneRules, see ZoneRulesProvider.

Time-zones 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 region ID. 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'.

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.

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static Map<String,String>	OLD_IDS_POST_2005 A map of zone overrides to enable the older US time-zone names to be used.
static Map<String,String>	OLD_IDS_PRE_2005 A map of zone overrides to enable the older US time-zone names to be used.

Method Summary

Methods

Modifier and Type	Method and Description
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.
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.
String	getText(TextStyle style, Locale locale) Gets the textual representation of the zone, such as 'British Time' or '+02:00'.
int	hashCode() A hash code for this time-zone ID.
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	systemDefault() Gets the system default time-zone.
String	toString() Outputs this zone as a String, using the ID.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

OLD_IDS_PRE_2005

public static final Map<String,String> OLD_IDS_PRE_2005

A map of zone overrides to enable the older US time-zone names to be used.

This maps as follows:

• EST - America/Indianapolis
• MST - America/Phoenix
• HST - Pacific/Honolulu
• ACT - Australia/Darwin
• AET - Australia/Sydney
• AGT - America/Argentina/Buenos_Aires
• ART - Africa/Cairo
• AST - America/Anchorage
• BET - America/Sao_Paulo
• BST - Asia/Dhaka
• CAT - Africa/Harare
• CNT - America/St_Johns
• CST - America/Chicago
• CTT - Asia/Shanghai
• EAT - Africa/Addis_Ababa
• ECT - Europe/Paris
• IET - America/Indiana/Indianapolis
• IST - Asia/Kolkata
• JST - Asia/Tokyo
• MIT - Pacific/Apia
• NET - Asia/Yerevan
• NST - Pacific/Auckland
• PLT - Asia/Karachi
• PNT - America/Phoenix
• PRT - America/Puerto_Rico
• PST - America/Los_Angeles
• SST - Pacific/Guadalcanal
• VST - Asia/Ho_Chi_Minh

The map is unmodifiable.

OLD_IDS_POST_2005

public static final Map<String,String> OLD_IDS_POST_2005

A map of zone overrides to enable the older US time-zone names to be used.

This maps as follows:

• EST - -05:00
• HST - -10:00
• MST - -07:00
• ACT - Australia/Darwin
• AET - Australia/Sydney
• AGT - America/Argentina/Buenos_Aires
• ART - Africa/Cairo
• AST - America/Anchorage
• BET - America/Sao_Paulo
• BST - Asia/Dhaka
• CAT - Africa/Harare
• CNT - America/St_Johns
• CST - America/Chicago
• CTT - Asia/Shanghai
• EAT - Africa/Addis_Ababa
• ECT - Europe/Paris
• IET - America/Indiana/Indianapolis
• IST - Asia/Kolkata
• JST - Asia/Tokyo
• MIT - Pacific/Apia
• NET - Asia/Yerevan
• NST - Pacific/Auckland
• PLT - Asia/Karachi
• PNT - America/Phoenix
• PRT - America/Puerto_Rico
• PST - America/Los_Angeles
• SST - Pacific/Guadalcanal
• VST - Asia/Ho_Chi_Minh

The map is unmodifiable.

Method Detail

systemDefault

public static ZoneId systemDefault()

Gets the system default time-zone.

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.

Returns:

the zone ID, not null

Throws:

DateTimeException - if the converted zone ID has an invalid format

ZoneRulesException - if the converted zone region ID cannot be found

of

public 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.

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.

Parameters:

zoneId - the time-zone ID, not null

aliasMap - a map of alias zone IDs (typically abbreviations) to real zone IDs, not null

Returns:

the zone ID, not null

Throws:

DateTimeException - if the zone ID has an invalid format

ZoneRulesException - if the zone region ID cannot be found

of

public static ZoneId of(String zoneId)

Obtains an instance of ZoneId from an ID ensuring that the ID is valid and available for use.

This method parses the ID, applies any appropriate normalization, and validates it against the known set of IDs for which rules are available.

An ID is parsed as though it is an offset ID if it starts with 'UTC', 'GMT', '+' or '-', or if it has less then two letters. The offset of zero may be represented in multiple ways, including 'Z', 'UTC', 'GMT', 'UTC0' 'GMT0', '+00:00', '-00:00' and 'UTC+00:00'.

Eight forms of ID are recognized, where '{offset}' means to parse using ZoneOffset.of(String):

• {offset} - a ZoneOffset ID, such as 'Z' or '+02:00'
• UTC - alternate form of a ZoneOffset ID equal to 'Z'
• UTC0 - alternate form of a ZoneOffset ID equal to 'Z'
• UTC{offset} - alternate form of a ZoneOffset ID equal to '{offset}'
• GMT - alternate form of a ZoneOffset ID equal to 'Z'
• GMT0 - alternate form of a ZoneOffset ID equal to 'Z'
• GMT{offset} - alternate form of a ZoneOffset ID equal to '{offset}'r
• {regionID} - full region ID, loaded from configuration

Region IDs must match the regular expression [A-Za-z][A-Za-z0-9~/._+-]+.

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.

Parameters:

zoneId - the time-zone ID, not null

Returns:

the zone ID, not null

Throws:

DateTimeException - if the zone ID has an invalid format

ZoneRulesException - if the zone region ID cannot be found

from

public static ZoneId from(TemporalAccessor temporal)

Obtains an instance of ZoneId from a temporal object.

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 in queries via method reference, ZoneId::from.

Parameters:

temporal - the temporal object to convert, not null

Returns:

the zone ID, not null

Throws:

DateTimeException - if unable to convert to a ZoneId

getId

public abstract String getId()

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

getRules

public abstract ZoneRules getRules()

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 JVM which does not have the same rules loaded as the JVM that stored it. In this case, calling this method will throw an exception.

The rules are supplied by ZoneRulesProvider. An advanced provider may support dynamic updates to the rules without restarting the JVM. 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

Throws:

DateTimeException - if no rules are available for this ID

getText

public String getText(TextStyle style,
             Locale locale)

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

This returns a textual description for the time-zone ID.

If no textual mapping is found then the full ID is returned.

Parameters:

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

equals

public boolean equals(Object obj)

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

The comparison is based on the ID.

Overrides:

equals in class Object

Parameters:

obj - the object to check, null returns false

Returns:

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

hashCode

public int hashCode()

A hash code for this time-zone ID.

Overrides:

hashCode in class Object

Returns:

a suitable hash code

toString

public String toString()

Outputs this zone as a String, using the ID.

Overrides:

toString in class Object

Returns:

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