Design issues

Question

Hello there,
I have 4 classes.
1. User
2. Client
3. UserManager
4. ClientManager
User is an abstract class and Client inherits from User. Therefore, a Client is a User.
UserManager is solely responsible for User objects management. It handles adding, removing, editing and getting all Users. Moreover, UserManager internally caches all Users objects using a List.
In structure sense, ClientManager works pretty much the same way as UserManager. Client objects are cached internally having the same functionalities like UserManager; adding, removing, etc.
The problem is caching Users and Clients result in duplicate data. Lets say User has the following properties:
1. String userName
2. String password
Since Client inherits from User, Client possesses these properties as well. Therefore, both caches store the same data.
What I hope to resolve:
Is there any way I can manage only set of User data? This can really be a big problem if I want to index these data.
Perhaps anyone can recommend a design pattern or something to effectively manage a set of data?
Thanks in advance.
Regards

Answer 1

Let me give an example.
Lets say if I want to add a new Client. I would use ClientManager to add this new Client.
ClientManager.register(Client newClient)Internally, UserManager does its own caching and indexing of User objects, like ClientManager, caching and indexing of Client objects.
Since I am using Decorator, UserManager shares the same interface as ClientManager.
UserManager.register(User newUser)register() from UserManager will be called first when I invoked ClientManager.register().
Invoking register() triggers the indexing and caching mechanism. Which means, I am indexing userName and password in UserManager and indexing the inherited userName and password again in ClientManager.
I can definitely change Client not to inherit from User but that will leave Client without a set of principal and credentials.