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interfaces

4 replies on 1 page. Most recent reply: Apr 28, 2004 5:28 AM by Matthias Neumair

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Nancy

Posts: 11
Nickname: ac121107
Registered: Feb, 2004

interfaces

Posted: Apr 27, 2004 12:46 AM

how interfaces compare to abstract classes?
Nancy

Matthias Neumair

Posts: 660
Nickname: neumi
Registered: Sep, 2003

Re: interfaces

Posted: Apr 27, 2004 1:38 AM

Here are the main differences:

A abstract class normally is a complete class wich requires some additional methods.

A Interface just makes sure the implementing class offers some methods.
A Interface has no methods

You can implement multiple Interfaces
(Using a abstract class you can extend only one class with all it's super classes)

A interface has no super class, so there is no restriction how and where to use it.

twc

Posts: 129
Nickname: twc
Registered: Feb, 2004

Re: interfaces

Posted: Apr 27, 2004 7:03 AM

>A interface has no super class, so there is no restriction how and where to use it.

This isn't entirely correct. Some interfaces do have super/sub interfaces. For example, java.awt.ItemSelectable is a super-interface for javax.swing.ButtonModel. LayoutManager and LayoutManager2 are also related through inheritance (LayoutManager2 is the sub-interface).

However, MOST interfaces do not have super or sub interfaces.

Adam Duffy

Posts: 168
Nickname: adamduffy
Registered: Feb, 2003

Re: interfaces

Posted: Apr 27, 2004 3:38 PM

For information on Object-Oriented Programming Concepts see
http://java.sun.com/docs/books/tutorial/java/concepts/index.html

For information on Classes and Inheritance
http://java.sun.com/docs/books/tutorial/java/javaOO/index.html

Finally, for Abstract Classes and Methods
http://java.sun.com/docs/books/tutorial/java/javaOO/abstract.html

No sense in redoing what has already been done (or reexplaining what has already been explained, as the case may be).

HTH,
Adam

Matthias Neumair

Posts: 660
Nickname: neumi
Registered: Sep, 2003

Re: interfaces

Posted: Apr 28, 2004 5:28 AM

Ok, my choice of words was not the best.
I meant, it does not EXTEND a class, but it can IMPLEMENT other interfaces.

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