use a method from class after factory class

I have a question.

I want use a method from a class, using its interface ( for istantiate it) after i have used a factory class.

Example:

public class UserBusiness{

    DAO_Interface DAO = DAO_Factory.getDAO("USER");

    public User Login(User user){
        User userx = DAO.LoginDAO(user);
        return userx;
        }

}

public class DAO_Factory {

    public static DAO_Interface getDAO(String type) {
        switch(type){

        case "USER" : {

            return new DAO_User();  

        }

public class DAO_User implements DAO_Interface{

    User userx;

    public DAO_User() { }


    public User LoginDAO(User user){
       // find data from Database 

        return userx;
    }

        @Override
    public Connection getConnetion() {
        // TODO Auto-generated method stub
        return null;
    }


}


public interface DataAccessObject {

    Connection getConnetion();

}

why don't work? i want use Interface only for method to connect every DAO(concrete) with database. Because i'm using many Entity class (as like as User), and only UserDao use a EntityClass User.

thanks a lot.