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package java.util.spi;
import java.util.Locale;
/**
* <p>
* This is the super class of all the locale sensitive service provider
* interfaces (SPIs).
* <p>
* Locale sensitive service provider interfaces are interfaces that
* correspond to locale sensitive classes in the <code>java.text</code>
* and <code>java.util</code> packages. The interfaces enable the
* construction of locale sensitive objects and the retrieval of
* localized names for these packages. Locale sensitive factory methods
* and methods for name retrieval in the <code>java.text</code> and
* <code>java.util</code> packages use implementations of the provider
* interfaces to offer support for locales beyond the set of locales
* supported by the Java runtime environment itself.
* <p>
* <h4>Packaging of Locale Sensitive Service Provider Implementations</h4>
* Implementations of these locale sensitive services are packaged using the
* <a href="../../../../technotes/guides/extensions/index.html">Java Extension Mechanism</a>
* as installed extensions. A provider identifies itself with a
* provider-configuration file in the resource directory META-INF/services,
* using the fully qualified provider interface class name as the file name.
* The file should contain a list of fully-qualified concrete provider class names,
* one per line. A line is terminated by any one of a line feed ('\n'), a carriage
* return ('\r'), or a carriage return followed immediately by a line feed. Space
* and tab characters surrounding each name, as well as blank lines, are ignored.
* The comment character is '#' ('\u0023'); on each line all characters following
* the first comment character are ignored. The file must be encoded in UTF-8.
* <p>
* If a particular concrete provider class is named in more than one configuration
* file, or is named in the same configuration file more than once, then the
* duplicates will be ignored. The configuration file naming a particular provider
* need not be in the same jar file or other distribution unit as the provider itself.
* The provider must be accessible from the same class loader that was initially
* queried to locate the configuration file; this is not necessarily the class loader
* that loaded the file.
* <p>
* For example, an implementation of the
* {@link java.text.spi.DateFormatProvider DateFormatProvider} class should
* take the form of a jar file which contains the file:
* <pre>
* META-INF/services/java.text.spi.DateFormatProvider
* </pre>
* And the file <code>java.text.spi.DateFormatProvider</code> should have
* a line such as:
* <pre>
* <code>com.foo.DateFormatProviderImpl</code>
* </pre>
* which is the fully qualified class name of the class implementing
* <code>DateFormatProvider</code>.
* <h4>Invocation of Locale Sensitive Services</h4>
* <p>
* Locale sensitive factory methods and methods for name retrieval in the
* <code>java.text</code> and <code>java.util</code> packages invoke
* service provider methods when needed to support the requested locale.
* The methods first check whether the Java runtime environment itself
* supports the requested locale, and use its support if available.
* Otherwise, they call the <code>getAvailableLocales()</code> methods of
* installed providers for the appropriate interface to find one that
* supports the requested locale. If such a provider is found, its other
* methods are called to obtain the requested object or name. If neither
* the Java runtime environment itself nor an installed provider supports
* the requested locale, a fallback locale is constructed by replacing the
* first of the variant, country, or language strings of the locale that's
* not an empty string with an empty string, and the lookup process is
* restarted. In the case that the variant contains one or more '_'s, the
* fallback locale is constructed by replacing the variant with a new variant
* which eliminates the last '_' and the part following it. Even if a
* fallback occurs, methods that return requested objects or name are
* invoked with the original locale before the fallback.The Java runtime
* environment must support the root locale for all locale sensitive services
* in order to guarantee that this process terminates.
* <p>
* Providers of names (but not providers of other objects) are allowed to
* return null for some name requests even for locales that they claim to
* support by including them in their return value for
* <code>getAvailableLocales</code>. Similarly, the Java runtime
* environment itself may not have all names for all locales that it
* supports. This is because the sets of objects for which names are
* requested can be large and vary over time, so that it's not always
* feasible to cover them completely. If the Java runtime environment or a
* provider returns null instead of a name, the lookup will proceed as
* described above as if the locale was not supported.
*
* @since 1.6
*/
public abstract class LocaleServiceProvider {
/**
* Sole constructor. (For invocation by subclass constructors, typically
* implicit.)
*/
protected LocaleServiceProvider() {
}
/**
* Returns an array of all locales for which this locale service provider
* can provide localized objects or names.
*
* @return An array of all locales for which this locale service provider
* can provide localized objects or names.
*/
public abstract Locale[] getAvailableLocales();
}