Summary

Enhance java.util.Locale and related APIs to implement additional Unicode extensions of BCP 47 language tags.

Goals

Support for BCP 47 language tags was was initially added in Java SE 7, with support for the Unicode locale extension limited to calendars and numbers. This JEP will implement more of the extensions specified in the latest LDML specification, in the relevant JDK classes.

Non-Goals

Unicode language-tag extensions other than those described below will be ignored.

Description

As of Java SE 9, the supported BCP 47 U language-tag extensions are ca and nu. This JEP will add support for the following additional extensions:

• cu (currency type)
• fw (first day of week)
• rg (region override)
• tz (time zone)

In order to support these additional extensions, changes will be made to the following APIs:

• java.text.DateFormat::get*Instance will return instances based on the extensions ca, rg and/or tz
• java.text.DateFormatSymbols::getInstance will return instances based on the extension rg
• java.text.DecimalFormatSymbols::getInstance will return instances based on the extension rg
• java.text.NumberFormat::get*Instance will return instances based on the extensions nu and/or rg
• java.time.format.DateTimeFormatter::localizedBy will return DateTimeFormatter instances based on the extensions ca, rg, and/or tz
• java.time.format.DateTimeFormatterBuilder::getLocalizedDateTimePattern will return pattern string based on the rg extension.
• java.time.format.DecimalStyle::of will return DecimalStyle instances based on the extensions nu, and/or rg
• java.time.temporal.WeekFields::of will return WeekFields instances based on the extensions fw and/or rg
• java.util.Calendar::{getFirstDayOfWeek,getMinimalDaysInWeek} will return values based on the extensions fw and/or rg
• java.util.Currency::getInstance will return Currency instances based on the extensions cu and/or rg
• java.util.Locale::getDisplayName will return a string that includes display names for these U extensions
• java.util.spi.LocaleNameProvider will have new SPIs for the keys and types of these U extensions

Risks and Assumptions

The display names returned from Locale::getDisplayName depend on the localized data provided by each locale provider.