URL stream handler service-provider class.
A URL stream handler provider is a concrete subclass of this class that
has a zero-argument constructor. URL stream handler providers may be
installed in an instance of the Java platform by adding them to the
application class path.
A URL stream handler provider identifies itself with a
provider-configuration file named java.net.spi.URLStreamHandlerProvider in
the resource directory META-INF/services. The file should contain a list of
fully-qualified concrete URL stream handler provider class names, one per
line.
URL stream handler providers are located at runtime, as specified in the
URL constructor.
