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Is it necessary for an abstract class to have at least one abstract method?
Started by java_geek on
, 6 posts
by 6 people.
Answer Snippets (Read the full thread at stackoverflow):
Note when ....
In JDK 1.0 it was indeed necessary to have at least one abstract method in an abstract class to use the destructor.
It may not make any.
No - you can declare a class abstract without having any abstract methods.
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Hi I have a doubt regarding HttpServlet class is an abstract class even though there is not any abstract method in the class , all methods are concrete. Can class be abstract even if does not have any abstract methods? If yes Whats the use?
Thanks
Answer Snippets (Read the full thread at stackoverflow):
If the class is abstract, you can't create an instance of that class sense to have an unspecialised instance of that class....
It's a matter of intent.
One cannot instantiate abstract classes so you have to subclass them in order to use work.
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Public abstract class A { public abstract void Process(); } public abstract class B : A { public abstract override void Process(); } public class C : B { public override void Process() { Console.WriteLine("abc"); } }
This code throws an Compilation Error...
Started by Alon on
, 7 posts
by 7 people.
Answer Snippets (Read the full thread at stackoverflow):
This code is equivalent:
public abstract class A { public abstract void Process(); } public ....
B inherits it anyway from A, and since B itself is abstract, you do not explicitly to have the 'override' in B.
Completely in class B.
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Please help :/
In Java you can create an abstract class that contains only abstract methods. On the other hand, you can create an interface that declares the same methods. So can you use abstract classes instead of interfaces?
Cheers!
Started by Registered User on
, 9 posts
by 9 people.
Answer Snippets (Read the full thread at stackoverflow):
The other "problem....
Abstract classes specify implementation.
In general you should use the rule:
Interfaces specify behaviour.
However, it hardly ever a good idea to do so .
In some cases you can use an abstract class instead of interface.
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Let's say I have an abstract class called ViewController, and another abstract class called FormViewController. When someone wants to create a form, he must subclass FormViewController and implement its abstract classes.
ViewController defines an abstract...
Started by openfrog on
, 3 posts
by 3 people.
Answer Snippets (Read the full thread at stackoverflow):
Yes, actually thats a widelly used design pattern on many OOP languages. .
The best way to prove it is to try it and see .
It's okay with any object-oriented language.
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In OOP, I see a lot of classes which derive from parent classes, but the parent classes are not marked as abstract. When the class IS marked as abstract, what advantage does this provide?
Thanks
Started by dotnetdev on
, 7 posts
by 7 people.
Answer Snippets (Read the full thread at stackoverflow):
Essentially, the abstract definition on a class indicates that it was not intended to be instantiated it?
The difference is really pretty pragmatic....
An abstract class cannot be instantiated by itself; it must be derived from to be instantiated.
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In past couple of days, I have read about quite a lot about dependency injection/inversion of control/inversion of dependency. I think that, now my understanding of the concept is much better. But I still don't get the following from wikipedia:
A. High...
Started by Sandbox on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
Wow, that was abstract..
Of the gap between them - that is the job of the abstraction.
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I am creating an abstract class. I want each of my derived classes to be forced to implement a specific signature of constructor. As such, I did what I would have done has I wanted to force them to implement a method, I made an abstract one.
public abstract...
Started by Anthony D on
, 5 posts
by 5 people.
Answer Snippets (Read the full thread at stackoverflow):
If the classes do not ....
You to an object of a derived class, define an abstract method which needs to be implemented by derived classes.
What exactly do you need this for? We might be able to suggest a work around for this .
Be abstract.
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An abstract base class (interface class) usually has all its member functions abstract. However, I have several cases where member functions consisting of calls to the abstract methods of the interface are used. I can implement them in a derived-but-still...
Started by andreas buykx on
, 7 posts
by 7 people.
Answer Snippets (Read the full thread at stackoverflow):
It okay for....
Now I would implementation.
If you really want an interface, it is probably best to use your second of the template method pattern - it's a concrete implementation based on calling abstract methods.
In an abstract base class.
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I've written a JavaScript application that runs off Prototype & Scriptaculous. I'm thinking of rolling it out in as an open source product & would like it to be able to run on jQuery as well — I typically use jQuery for most of my other apps, except the...
Started by zemaj on
, 4 posts
by 4 people.
Answer Snippets (Read the full thread at stackoverflow):
The key difference is that they are using a 1-to-1 model where you say which library... .
They have a concept of "adapters" which allow you to sit Ext.JS on top of any of the underlying libraries and it will just work .
I believe Ext.Js does something similar.
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