Hey Miga! Thanks for your response. I'll have to search the forum, as I'm still not any more clear on the subject. It seems to me that a Manager would, by definition, also be seen as a Person. If you're saying that this is more useful when you've got a class hierarchy that's more than one parent and one child, I'm starting to get it, I'm just still not 100% sure why.
Thanks! Cheers, -m On Wed, Apr 1, 2009 at 1:40 PM, miga <migat...@gmail.com> wrote: > > > > On Apr 1, 10:26 pm, "maa...@gmail.com" <maa...@gmail.com> wrote: > > Hi All, > > > > I apologize if this question has been answered, but I've read all the > > lessons and supporting material (up to "inner class," at least) and I've > > spoken to a colleague who has taken a similar intro to Java class, but I > > still can't figure this out. > > > > My question is this: I know that it's possible to do have a simple class > > hierarchy like this: > > > > Animal > > -----Dog > > > > And to create an object like this: > > > > Animal dog1 = new Dog(); > > > > But I'm curious as to why you would do that when you can just write: > > > > Dog dog1 = new Dog(); > > > > because it seems like either way the compiler would know that a Dog > object > > is a subclass of Animal, right? Is it partially for code readability? > > > > Can anyone give me an example of where you'd want to use one method over > the > > other, and what the benefits (e.g. performance) might be when using one > > method over the other? > You may search the forum, this question has been answered recently in > great details. > However, here is a reason why you may want to use the superclass to > define an instance. > Say you have a set of person, that is a Person class. Now you have a > set of managers, that is a Manager class. Obviously Manager is a > subclass of Person. Now you have a set of employees, that is an > Employee class. Employee is also obviously a subclass of Person. And > seeing from the point of view of the Entreprise (a new class), a > manager -aka an instance of the Manager class) is also an employee (an > instance of the Employee class). > But you cannot say directly Brian is a Manager and an Employee; as > with Dog dog1 = new Dog(), on the contrary you may say: Person brian = > new Manager(), that's just a way to make brian viewed as a person who > is also a manager; and as he is a person, you may thereafter view him > as an employee. > > > > -- Love is a snowmobile racing across the tundra and then suddenly it flips over, pinning you underneath. At night, the ice weasels come. - Matt Groening --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to javaprogrammingwithpassion@googlegroups.com To unsubscribe from this group, send email to javaprogrammingwithpassion-unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/javaprogrammingwithpassion?hl=en -~----------~----~----~----~------~----~------~--~---
