Consider I have classes as follows:

public class User{     private String name;     //other code     private String getName(){         return name;     } }  public class ShowUserInfo{     public void show(User user){         System.out.println(user.getName());     } } 

I’m quite sure I would not have other variations of User, and doesn’t require polymorphism for User. But it is violating the rule of “dependency inversion principle” : ShowUserInfo depends on concrete class User, instead of abstractions. My question is, should I create interface for User:

public interface User{     String getName(); }  public class UserImp implements User{     private String name;     //other code     @Override     private String getName(){         return name;     } } 

even if I don’t need polymorphism and quite sure it would have one type of User only?