How can I create a SIP connecton using Liblinphone interface class?

I'm new to Java and want to develop a SIP client for Android using Liblinphone library.
There is a LinphoneAuthInfo class that accepts authentication.
And a LinphoneCore.addAuthInfo() That adds authentication info to the core.

**The problem is that I cannot initialize LinphoneAuthInfo and LinphoneCore classes because they are interface classes and I don't know how to use theme.**

If they was not interface classes I would do this:

Code:

---

// Create Authentication object
LinphoneAuthInfo authInfos;
authInfos.setDomain(id);
authInfos.setUserId(username);
authInfos.setPassword(password);

// Config Core
LinphoneCore linCore;
linCore.addAuthInfo(authInfos);

---

And finaly, this is the Liblinphone reference page:

http://www.linphone.org/docs/liblinp...phoneCore.html
http://www.linphone.org/docs/liblinp...eAuthInfo.html

And thanks for your help