In addition to what Jack said about AccessToken.getAccessToken() returning the string value of accessToken, you can avoid instantiating DefaultFacebookClient
twice by extending DefaultFacebookClient
like this:
import com.restfb.DefaultFacebookClient;
public class LoggedInFacebookClient extends DefaultFacebookClient {
public LoggedInFacebookClient(String appId, String appSecret) {
AccessToken accessToken = this.obtainAppAccessToken(appId, appSecret);
this.accessToken = accessToken.getAccessToken();
}
}