Hi Tanya
Let me help you with something…
The difference is in the way the Person is used, for example you can define a
Person like this
Person John = new Person();
And if you like this Person to Play FootBall, then you can create a function
like this:
void playFootball(FootballInterface x)
{
… /* Implement playing football */
}
Then you can call the function directly as: playFootball(John)
This is possible because John is a Person which implements the FootballInterface
Or you can do the same with:
FootballInterface JohnyPlayer = new Person();
playFootball(JohnyPlayer);
CONCLUSION: If you declare an instance of Person, then it can be “used” easily
with functions that requires this kind of interface.
Hope it helps
Patricio
De: [email protected]
[mailto:[email protected]] En nombre de Tanya Dina
Ruttenberg
Enviado el: viernes, 27 de febrero de 2009 9:27
Para: [email protected]
CC: [email protected]; [email protected]
Asunto: [java programming] Re: Interfaces lesson - question
Thanks Keith. But I still don't really get it.
Suppose I have a class Person which implements several interfaces. My person
class is a Dad and a doctor and likes
to play football on weekends.
class Person implements DadInterface, DoctorProfessionalInterface,
FootballInterface {
}
In my program I set up 3 objects like these:
FootballInterface person2 = new Person();
DadInterface dad1 = new Person();
Person person3 = new Person();
What is the difference between person2, dad1, and person3? Don't they have all
the same properties and
methods as any Person()?
Feb 26, 2009 10:49:55 PM, [email protected] wrote:
Tanya,
An interface is a way to abstract. Interface is more a design than an
implementation. You can use Interfaces to handle different typed objects. In
the case below it is true that type declaring as a class works but is not
recommened. I think this is because the class Person implements the
PersonInterface. For someone to look at and maintain the code they might think
that "pc" was an abstract class and not an interface. So simply declaring an
object "pi" of type PersonInterface and object class Person makes sense.
It makes more sense once you implment more than one interface or multiple
interfaces. So think of Person implementing multiple interfaces and the type
PersonInterface declaration makes more sense. In general it seems to me that if
there are multiple interfaces for a class to inherit, that is when we use
interface and not just class. I also read somewhere that if you create an
abstract class with all the methods abstract, that is really an interface.
Keith
_____
From: Tanya Dina Ruttenberg <[email protected]>
To: [email protected]
Sent: Thursday, February 26, 2009 2:48:29 PM
Subject: [java programming] Interfaces lesson - question
In http://www.javapassion.com/javase/javainterface.pdf page 21 it says
Interfaces and classes are both types
– This means that an interface can be used in places
where a class can be used
– For example:
// Recommended practice <<----
PersonInterface pi = new Person(); <<----
// Not recommended practice <<----
Person pc = new Person(); <<----
Why would it be the recommended practice to type a new object by its interface
name?
Tanya
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