How to check for an internal class in another module from java.base?

[Wang Weijun]

HTTP Negotiate uses

  Class.forName("sun.net.www.protocol.http.spnego.NegotiatorImpl", true, null);

to check if the implementation in java.security.jgss module is provided. It 
looks like this call is throwing a ClassNotFoundException now. Shall I export 
the package to java.base or is there any other trick? I remember there used to 
be an addReads method but seems no one is using it now.

Or I must use a service loader?

Thanks
Max