interface Store<T extends Base> {
    void add(T t);
    Simple<T> getStore();
    boolean delete(T t);
    boolean update(T oldObj, T newObj);
}

class UserStore implements Store<User> {
    private Simple<User> users = new SimpleArray<>();

    @Override
    public void add(User user) {
        users.add(user);
    }

    public Simple<User> getStore() {
        return users;
    }

    @Override
    public boolean delete(User user) {
        for (int i = 0; i < users.getSize(); i++) {
            if (user.getId().equals(users.get(i).getId())) {
                users.delete(i);
                return true;
            }
        }
        return false;
    }

    @Override
    public boolean update(User oldObj, User newObj) {
        for (int i = 0; i < users.getSize(); i++) {
            if (oldObj.getId().equals(users.get(i).getId())) {
                users.update(i, newObj);
                return true;
            }
        }
        return false;
    }
}

class RoleStore implements Store<Role> {
    private Simple<Role> roles = new SimpleArray<>();

    @Override
    public void add(Role role) {
        roles.add(role);
    }

    public Simple<Role> getStore() {
        return roles;
    }

    @Override
    public boolean delete(Role user) {
        for (int i = 0; i < roles.getSize(); i++) {
            if (user.getId().equals(roles.get(i).getId())) {
                roles.delete(i);
                return true;
            }
        }
        return false;
    }

    @Override
    public boolean update(Role oldObj, Role newObj) {
        for (int i = 0; i < roles.getSize(); i++) {
            if (oldObj.getId().equals(roles.get(i).getId())) {
                roles.update(i, newObj);
                return true;
            }
        }
        return false;
    }
}

И сам контент для сторов:
public abstract class Base {
    private final String id;

    Base(String id) {
        this.id = id;
    }

    public String getId() {
        return id;
    }
}

public class Role extends Base {
    public Role(String id) {
        super(id);
    }
}

public class User extends Base {
    public User(String id) {
        super(id);
    }
}

public interface Base;
public class User implements Base {};
public class Role implements Base {};

public abstract class GenericStore <T extends Base> implements Store <T>
{
    private Simple <T> items = new Simple <T> ();

    public void add(T item)
    {
        items.add(item);
    }
}

Store<User> UserStore = new GenericStore<User>():
UserStore.add(new User());