Add @Stable to LocaleProviderAdapter

[wenshao]

I read @minberg 's PR #25727 (JDK-8359119: Change Charset to use StableValue ) and found that LocaleProviderAdapter can also be optimized.

1. We can provide the adapter field in LocaleProviderAdapter$Type and replace the original ConcurrentMap.putIfAbsent with LazyInit + Stable

public abstract class LocaleProviderAdapter {
    public enum Type {
        @Stable
        private volatile LocaleProviderAdapter adapter;
    }
}

2. In LocaleProviderAdapter$Type::getAdapter, switch + new is used instead of the original reflection, which can improve startup performance and maintainability.

        private synchronized LocaleProviderAdapter getAdapter0() {
            if (adapter == null) {
                // lazily load adapters here
                adapter = switch (this) {
                    case JRE -> new JRELocaleProviderAdapter();
                    case CLDR -> new CLDRLocaleProviderAdapter();
                    case SPI -> new SPILocaleProviderAdapter();
                    case HOST -> new HostLocaleProviderAdapter();
                    case FALLBACK -> new FallbackLocaleProviderAdapter();
                    default -> throw new ServiceConfigurationError("Locale provider adapter \"" +
                            this + "\"cannot be instantiated.");
                };
            }
            return adapter;
        }

3. Using multiple ifs in LocaleProviderAdapter instead of ConcurrentHashMap.putIfAbsent allows C2 Inline to optimize unnecessary code branches

    private static ConcurrentMap<Locale, LocaleProviderAdapter> getAdapterMap(Class<? extends LocaleServiceProvider> providerClass) {
        if (providerClass == BreakIteratorProvider.class)           return breakIteratorProviderAdapterMap;
        if (providerClass == CollatorProvider.class)                return collatorProviderAdapterMap;
        if (providerClass == DateFormatProvider.class)              return dateFormatProviderAdapterMap;
        if (providerClass == DateFormatSymbolsProvider.class)       return dateFormatSymbolsProviderAdapterMap;
        if (providerClass == DecimalFormatSymbolsProvider.class)    return decimalFormatSymbolsProviderAdapterMap;
        if (providerClass == NumberFormatProvider.class)            return numberFormatProviderAdapterMap;
        if (providerClass == CurrencyNameProvider.class)            return currencyNameProviderAdapterMap;
        if (providerClass == LocaleNameProvider.class)              return localeNameProviderAdapterMap;
        if (providerClass == TimeZoneNameProvider.class)            return timeZoneNameProviderAdapterMap;
        if (providerClass == CalendarDataProvider.class)            return calendarDataProviderAdapterMap;
        if (providerClass == CalendarNameProvider.class)            return calendarNameProviderAdapterMap;
        if (providerClass == CalendarProvider.class)                return calendarProviderAdapterMap;
        if (providerClass == JavaTimeDateTimePatternProvider.class) return javaTimeDateTimePatternProviderAdapterMap;
        throw new InternalError("should not come down here");
    }

In this way, calls like the following can fold away unnecessary branches

  adapter = LocaleProviderAdapter.getAdapter(NumberFormatProvider.class,
                desiredLocale);

4. In the JRELocaleProviderAdapter::getLocaleServiceProvider method, use multiple ifs instead of switch(String) so that CodeSize < 325 can be inlined

5. Add @stable to the immutable fields of FallbackLocaleProviderAdapter/JRELocaleProviderAdapter/CLDRLocaleProviderAdapter

---

Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/26354/head:pull/26354
$ git checkout pull/26354

Update a local copy of the PR:
$ git checkout pull/26354
$ git pull https://git.openjdk.org/jdk.git pull/26354/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 26354

View PR using the GUI difftool:
$ git pr show -t 26354

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk/pull/26354.diff

[bridgekeeper]

👋 Welcome back swen! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

@wenshao The following labels will be automatically applied to this pull request:

• core-libs
• i18n

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing lists. If you would like to change these labels, use the /label pull request command.