• RELEVANCY SCORE 4.89

    DB:4.89:Abstract Class 13




    Difference between abstract class and interface
    use of abstract class

    DB:4.89:Abstract Class 13

    This question has been asked here about a billion times:

    http://search.java.sun.com/search/java/index.jsp?qt=interfacenh=10qp=st=11rf=0since=country=language=charset=variant=col=javaforums

  • RELEVANCY SCORE 4.78

    DB:4.78:Interface, Abstract Class E Sealed Class 1d




    Bom dia a todos,
    O conceito de quando utilizar cada tipo de classe(Interface, Abstract class e Sealed Class ) pode parecer um pouco confuso as vezes!
    Algum pode me dar umas dicas e quando usar cada tipo de classe?
    Obrigado!David Ramires

    DB:4.78:Interface, Abstract Class E Sealed Class 1d

    Obrigado! pena que ninguem mais quer participar!David Ramires

  • RELEVANCY SCORE 4.45

    DB:4.45:Abstract Class Vs Interface 9d




    Hi

    I was just wondering what is the advantage of using an abstract class over interface. In what situation, using an abstract class is more suitable than using interface? and vice versa?

    DB:4.45:Abstract Class Vs Interface 9d

    This question has been asked and answered a million times. For instance, see this thread: http://forum.java.sun.com/thread.jsp?forum=31thread=352322

  • RELEVANCY SCORE 4.35

    DB:4.35:Difference Between Abstract Class And Interface ca


    Hi everyone,

    CAn anyone explain why the following happen????

    --------------------------------------------------------------------------------
    Abstract class can have a constructor, Interface cannot.
    Abstract class can have static methods, Interface cannot.
    --------------------------------------------------------------------------------

  • RELEVANCY SCORE 4.31

    DB:4.31:Abstract Class And Interface x7


    Hi,
    Can anyone explain why we use abstract class and interface
    and when we use abstract class and interface
    and which one is best to use
    please explain in simple words
    waiting for reply.....

    DB:4.31:Abstract Class And Interface x7

    Abstract classes and interfaces are very similar. In languages that support Multiple Inheritance (like native C) abstract classes are what is used for/instead Interfaces.
    Allas, Multiple Inheritance is a ugly thematic (for the guy who writes Compilers and for the programmer that writes the code). And hence the developers of .NET decided:
    A class can only inherit from on base class. For everything else, use interfaces. (they propably took that directly from Java) It is not the worst decision by the way, Polymorphy with Multiple Inheritances really is a headache (1-2 chapters in each C
    book).

    The differences are:
    A abstract class has to be in the Inheritance Chain.
    A abstract class can code out any functions and methods it defines. This includes (even if that may sound contra-intuitive) the Constructor (it is to be called using base()). It does not have too.
    A abstract class can define public Varriables. But with the advent of properties (wich are short syntaxes for Functions), this became mostly irrellevant.

    A Interface can't be part of the Inheritance Chain (but in a way Interfaces can inherit other interfaces, creating Interface chains).
    A interface can't code out any functions. It can only provide the signature (name, parameter types, return type).
    As properties are little more then a neat way to write get- and set-functions, a Interface
    can contain properties.
    What they have in similar:
    Neither can be instantiated.
    Both can be used as Varriable types (so it does not matter wich implementation of this Interface/A-Class you have). Indeed downcasting to the Abstract or Interface type is what you most often see them used for.
    Both force class that Inherit/Implement them to provide code for the Functions. You don't need to know how a IComparable figures out wich Instance is higher then the other. Nor how exactly a SQLConnection opens the Connection. You only need to know is has
    a Compare() and Open() Function respectively.
    When to use Abstract classes:
    You want thsi thing to be part of the Inheritance Chain.
    You want this Functionality to be the main job of whatever inherits from it. Example:
    DBConnection. The abstract baseclass of things like SQLConnection. The designers decided that a DBConnection should not also be a Window/Form. A DBConnection should be
    created for it's specific task (connecting to a DB), be used and then be thrown away (or in this case Diposing would be even better). Allowing it to be also a Window would only risk keeping it in memory to long wich can be uggly as it uses unmanaged resources.
    A similar example is
    Stream, the baseclass of FileStreams, memoryStreams and the like. You will find this often whenever dealing with input/umnaged resources.

    When to use Interfaces:
    Everytime you don't need an Abstract class. Or even the other way: Only use abstract classes is you really need them/want them.

    Interfaces are ideal for small functionality. For example,
    IComparable. When a class implements IComparable it can be sorted by the .Sort() function of a list. Yet, being sortable is not the main function of this class. It's job is propably to contain multiple data fields as a unit. Being sortable is just a small
    functionality to be added. But as long as this functionality is added by providing Code for IComparable.Compare(), it can be sorted! The writer of List did not need to know how it works. Just the return values are of interest.Let's talk about MVVM: http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/b1a8bf14-4acd-4d77-9df8-bdb95b02dbe2

  • RELEVANCY SCORE 4.23

    DB:4.23:What Is The Difference Between Abstract Class And Interface ? dd


    Hi,

    Could u plz tell me the difference between Abstract class and Interface?

    Thanks in advance.

    Gopi

    DB:4.23:What Is The Difference Between Abstract Class And Interface ? dd

    Lots.

    An abstract class can contain some method implementations, or indeed all the method implementations. It may contain methods with all the various access modifiers. It cannot be instantiated. A class may inherit from only a single abstract class.

    An interface contains only public method stubs and constants. A class may implement multiple interfaces. An interface cannot (obviously) be instantiated.

    Abstract classes are particularly useful when you need to provide a semi-complete implementation for reuse. Interfaces are used more like types.

    Look at java.util.* for some good examples of the use of both.

  • RELEVANCY SCORE 4.23

    DB:4.23:Constructor For Abstract Class 7c


    can any body tell me,
    if we cannot instantiate an abstract class, then why there is a need of constructor for abstract class.
    one more thing is that an interface not have an internal state, but abstract class can have, so any relation here for solution of my problem? explain me how?

  • RELEVANCY SCORE 4.23

    DB:4.23:Sealed Classes, Abstract Classes And Partial Classes m1


    hello,
    What is the different between a sealed class and an abstract class?.... and also iwant to know what is the purpose of a partial class?

    DB:4.23:Sealed Classes, Abstract Classes And Partial Classes m1

    I'd also like to add that an abstract class HAS TO BE inherited. You cannot directly instantiate an abstract class.~~Bonnie DeWitt [C# MVP]
    http://geek-goddess-bonnie.blogspot.com

  • RELEVANCY SCORE 4.23

    DB:4.23:Abstract Calss Vs Interface af


    hi all,

    what are the pros and cons of abstract calss and interface?
    when to use abstract class and when to use interface???

    thanks.

    DB:4.23:Abstract Calss Vs Interface af

    Well.. this is very basic question and asked many times. Googling this question may give you good results...

  • RELEVANCY SCORE 4.06

    DB:4.06:Ca1033 (Interface Methods Should Be Callable By Childtypes) - False Positive? k9


    "Make 'XYSeries' sealed (a breaking change if this class has previously shipped), implement the method non-explicitly, or implement a new method that exposes the functionality of 'IChartSeries.get_Name():String' and is visible to derived classes." public class TabularData { private string name; public string Name { get { return name; } set { name = value; } } } public interface IChartSeries{ string Name { get; set; } } public abstract class XYSeries : TabularData, IChartSeries {}

    DB:4.06:Ca1033 (Interface Methods Should Be Callable By Childtypes) - False Positive? k9

    Andrew,
    Thanks for chasing this down. I've reproduced this and filed a bug. The above code also appears to incorrectly fire ParameterNamesShouldMatchBaseDeclaration with the following message: Change parameter name 'param0' of method XYSeries.ClassLibrary3.IChartSeries.set_Name(String):Void to 'value' in order to match the identifier as it has been declared in IChartSeries.set_Name(String) :Void.
    Thanks for the feedback!
    Regards
    David

  • RELEVANCY SCORE 4.01

    DB:4.01:Abstract Class And Interface 3j


    I would covet to recognize at what situation we use abstract class
    and when to use interface?

    With Regards,
    Stalin.G

    DB:4.01:Abstract Class And Interface 3j

    http://www.google.com/search?q=abstract+class+interface+site:forum.java.sun.com

  • RELEVANCY SCORE 4.00

    DB:4.00:Question About Abstract Class mm


    2 questions
    1, can an abstract class implement an interface?
    2, i know an abstract class can extend other abstract classes, but can it extend a non-abstract class?
    Thank you for your time
    ~Gabor

    DB:4.00:Question About Abstract Class mm

    tjacobs01 wrote:
    BTW I suppose the final thing is also true of private classes, since they can't be extended.Y'know, if you're concerned about extending your privates, there are certain products on the market nowadays. I can forward you a slew of emails if you want.

  • RELEVANCY SCORE 3.94

    DB:3.94:When To Use Abstract Class And Interface 3z


    What is the scenario to use abstract class and interface

    DB:3.94:When To Use Abstract Class And Interface 3z

    Read this too, if you have time. :)
    http://java.sun.com/developer/JDCTechTips/2001/tt1106.html#tip2

  • RELEVANCY SCORE 3.94

    DB:3.94:How To Know When To Use Interface/Abstract Class dm


    Hi All

    Can someone please tell me the design time usage of Interface / Abstract class.

    DB:3.94:How To Know When To Use Interface/Abstract Class dm

    The best answer for this question I heard so far was: A class represents what an object IS and an interface what it CAN DO.

  • RELEVANCY SCORE 3.94

    DB:3.94:Abstract Class Inheriting Another Abstract Class ck


    If I have an "Abstract" class that has the following methods:

    Abstract A
    getX();
    abstract getY();
    abstract getXY();And, another "Abstract" class that "INHERITS" A:

    Abstract B extends AWill the "Abstract" methods in class A be ALSO "Abstract" in class B?

    Thanks.

    DB:3.94:Abstract Class Inheriting Another Abstract Class ck

    Think about it: the alternative would be they are no longer abstract methods -- so where did their mystery bodies come from?

  • RELEVANCY SCORE 3.94

    DB:3.94:Re: Oo Design Decision - Interface, Subclass Or Override d8


    just musing,

    abstract class Animal;
    abstract class Plant;
    class Cat extends Animal;
    class Dog extends Animal implements Tradable;
    class Wheat extends Plant implements Tradable;

    interface Tradable {
    public Object buy( Object obj );
    public Object sell( Object obj );
    }

    abstract class TradingSystem;
    class FreeMarket extends TradingSystem;
    class Barter extends TradingSystem;

    have not thought any further! :)

    DB:3.94:Re: Oo Design Decision - Interface, Subclass Or Override d8

    yes, but then for us, it is just for fun. it might not be for you :)

    d) Buy a book on patterns and read it before posting stupid questions on this forum I guess you have to
    have a really clear picture of what you want to have
    happen before you dive into a problem.

  • RELEVANCY SCORE 3.94

    DB:3.94:Abstract Class &Amp; Interface jp


    In which situation we use Abstract Class and in which situation we use Interface?

    DB:3.94:Abstract Class &Amp; Interface jp

    In which situation we use Abstract Class and in which
    situation we use Interface?It's a frequently asked question so search the forums.

    One answer is that from a pure typing perspective it doesn't matter because they're equal. The difference is that an abstract class can carry implementation, something an interface cannot. So pick the abstract class when you consider that beneficial.

  • RELEVANCY SCORE 3.90

    DB:3.90:Interface Abstract Class jc


    Hello,

    DB:3.90:Interface Abstract Class jc

    The example sited, as many, could be done with an abstract Account class, or with an Account interface. Given only the information in what you copied, An interface is resonable.

  • RELEVANCY SCORE 3.90

    DB:3.90:Abstract And Interface fa


    Dear Sir/Madam,

    Please let me know the difference between Abstract class and Interface.

    DB:3.90:Abstract And Interface fa

    I disappeared as i was checking the forums in javaworld.com, but now i will keep this site as main.

  • RELEVANCY SCORE 3.90

    DB:3.90:When To Use Abstract Class And Interface In Project Of Student Management 3j


    Can anyone explain me briefly Abstract Class and Interface
    In Project Of Student Management which class use as a Abstract class .

    DB:3.90:When To Use Abstract Class And Interface In Project Of Student Management 3j

    If it's a program you use you should post this question on the support forums of the program.

    Eyal (http://shilony.net), Regards.

  • RELEVANCY SCORE 3.90

    DB:3.90:Abstract Class Vs Interface 1x


    Hi I have a small doubt regarding this.
    When can i go for Abstract Class and When can i go for Interface.
    Anybody can help me?

    DB:3.90:Abstract Class Vs Interface 1x

    Hi I have a small doubt regarding this.
    When can i go for Abstract Class and When can i go for Interface.
    Anybody can help me?

  • RELEVANCY SCORE 3.90

    DB:3.90:Java Programming 33


    what is the difference between 'abstract' class and 'interface'

    DB:3.90:Java Programming 33

    Hey, get back in line. Don't jump the queue :)Well I guess I haven't qualified myself for this
    year's hunt. Maybe I could get a free-card because I
    was always on the Most Arrogant List a few years ago.Ok. I'll be nice. You'll get a free pass.

    Kaj

  • RELEVANCY SCORE 3.90

    DB:3.90:Abstract Class And Interface???? 39


    hi all, i would like to know the difference between abstract class and interface....could anybody enlighten me on this....

    DB:3.90:Abstract Class And Interface???? 39

    P.S. don't be a loser an put up multiple posts, especially on something so easy to do a search on.

  • RELEVANCY SCORE 3.90

    DB:3.90:Re: What Is The Difference Between An Interface And An Abstract Class? 1a


    8000 views already wow.

    DB:3.90:Re: What Is The Difference Between An Interface And An Abstract Class? 1a

    filestream wrote:
    As the two famous politicians, Jonathan Curry and Larry Craig are wont to say, "Glad I could serve you."

    Of course, each says it in entirely different situations but we're not here to discuss that. The members of the forums are happy just knowing that we've cleared 1 doubt.Now that you mention it, I take a wide stance in the interface/abstract class issue.

  • RELEVANCY SCORE 3.90

    DB:3.90:Abstract Class And Interface 97


    is it any differences between abstract class and interface?

    DB:3.90:Abstract Class And Interface 97

    And of course you [url http://onesearch.sun.com/search/developers/index.jsp?col=devforumsqp_name=Java+Programmingqp=forum%3A31qt=%22+differences+between+abstract+class+and+interface%22] searched first....

    Mike

  • RELEVANCY SCORE 3.90

    DB:3.90:Interface Vs Abstract Class sa


    when would you create an interface as opposed to an abstract class?

    DB:3.90:Interface Vs Abstract Class sa

    An interface solves the problem of multiple inheritance in Java. A class can only extend from one other class, but can implement multiple interfaces. I link to think of extending in a vertical fashion ( among a class hierarchy ), and interfaces in a horizontal fashion ( across classes that may have nothing in common ).

  • RELEVANCY SCORE 3.90

    DB:3.90:Difference Between Interface And Abstract Class mj


    hello friends give me the difference between interface and abstract class
    and link to find java material

    Thanx

  • RELEVANCY SCORE 3.90

    DB:3.90:Interface Vs Abstract Class 81


    hello
    what to use when between interface vs abstract class?
    and which one is better for decoupling and different version on software.
    regardsIt's Me

    DB:3.90:Interface Vs Abstract Class 81

    For a detailed discussion on this see:
    Abstract Class vs InterfaceJohn Grove - DSS, Senior Software Engineer

  • RELEVANCY SCORE 3.90

    DB:3.90:Interface Vs Abstract Class sz


    Let say that an abstract class has all abstract functions and someone use it instead of interface.
    What are the disadvantage and advantages?
    I know one that he cannot do multiple inheritance, hence he cannot extends abstract class and use any other parent Class. However, I wish to know more disadvantage/advantages.

    Looking forward for your input.

    --
    PS: I know interface cannot have code and abstract class could have code (non-abstract) methods.

    .

    DB:3.90:Interface Vs Abstract Class sz

    HowToDoIt wrote:
    Let say that an abstract class has all abstract functions and someone use it instead of interface.
    What are the disadvantage and advantages?
    I know one that he cannot do multiple inheritance, hence he cannot extends abstract class and use any other parent Class. However, I wish to know more disadvantage/advantages.

    Looking forward for your input.

    --
    PS: I know interface cannot have code and abstract class could have code (non-abstract) methods.

    .An Interface expresses a contract.
    A class implementing an interface is saying "I will supply implementations of all methods described in the interface, i.e. methods with those particular signatures"

    A class can of course implement multiple interfaces, i.e. it is capable of fulfilling multiple contracts.

    An Abstract class is used to provide a 'base' implementation of some specific functionality (whether it is described in an Interface or not).

    I cannot think of a useful purpose for an abstract class that contains only abstract methods (perhaps it inherits some behavior from its base class)

    Usually some methods in an abstract class WILL be implemented, either because they are unlikely to change in child classes, or they provide a guide/example of implementation, or the implemented methods may be defined in terms of some of the abstract methods, this allows classes which extend the abstract class to 'mix in' their behavior with that of the base abstract class.

    So Interface and Abstract Class have two distinct and separate purposes.

    I hope that is clear?

    Just to help with the details, you can put more than just method signatures in an interface, your could for example have in your interface

    public interface Face1
    {
    public static final int x = 3;
    }which you would access as:

    int fred = Face1.x;And you can place a public static class inside of your interface, the methods of which you would access in a similar way, but you should avoid this unless you really know what you are doing.

  • RELEVANCY SCORE 3.90

    DB:3.90:Abstact Class Or Interface d3


    why would one use an abstract class versus an interface?

    DB:3.90:Abstact Class Or Interface d3

    MachBork wrote:
    why would one use an abstract class versus an interface?Don't you think think that this has been asked here in this forum, oh say a gazillion times? Please learn to search the forum for all the many threads on this and other questions.

  • RELEVANCY SCORE 3.90

    DB:3.90:Abstract Class z3



    Hi to all,

    can any one tel me what are abstract classes and what hapens if i check the ABSTRACT ckeck box while creating a interface in se24(class builder)?

    Thanks Regards

    Priya

    DB:3.90:Abstract Class z3


    Thanks Matthew .

    Thanks Regards

    Priya

    Edited by: priya latha on Dec 19, 2007 11:43 AM

  • RELEVANCY SCORE 3.90

    DB:3.90:Interface And Abstract Class dc


    why we have constructor for abstract class and not for interface,

    DB:3.90:Interface And Abstract Class dc

    Simpler reason: interfaces have no implementation. Period.

  • RELEVANCY SCORE 3.90

    DB:3.90:Abstract Class &Amp; Interface 17


    What is the difference between Abstract Class and Interface Class? What I understood is both has to be defined in the subclass i.e methods. Apart from that Interface supports multiple inheritance whereas Abstract class doesn't. When both has to be defined in the subclass and interface supports multiple inheritance why we still need Abstract Class.

    Thanks in Advance,
    R.Ravindhran

    DB:3.90:Abstract Class &Amp; Interface 17

    A class can only extend one other class (Abstract or not) but it can implement any number of interfaces.

  • RELEVANCY SCORE 3.88

    DB:3.88:Re: Abstract Class-Interface kk


    why abstract class is faster than interface?

    Because mauve has the most RAM.

    ~

    DB:3.88:Re: Abstract Class-Interface kk

    Do you know any documentation about this of Sun's current JVM?No, sorry. If there are docs about this, [http://research.sun.com/techrep/] is probably a start. I believe that the Self Project [http://research.sun.com/self/] was also pretty influential and has some papers available.

    If you need a definite answer on how it is implemented in the current JVM and are fluent in C, you could take a look at HotSpot's source code. I browsed a bit (out of curiosity) and admittedly it's, well, complex (surprise! ;-) -- but given some time (and interest, of course) I guess one should be able to at least get an idea of how it works (fortunately there are some comments, too). I used OpenGrok here [http://opengrok.neojava.org/hotspot], and found some entry points for further investigation; maybe they're helpful:

    [http://12.101.252.19/hotspot/xref/src/share/vm/interpreter/cInterpretMethod.hpp], search for "CASE(_invokeinterface)"
    [http://12.101.252.19/hotspot/xref/src/share/vm/runtime/javaCalls.cpp#call_virtual]
    [http://12.101.252.19/hotspot/xref/src/share/vm/opto/doCall.cpp#do_call]

    [http://12.101.252.19/hotspot/xref/src/share/vm/oops/klassVtable.hpp]
    [http://12.101.252.19/hotspot/xref/src/share/vm/oops/klassVtable.cpp], "miranda methods"

    [http://12.101.252.19/hotspot/xref/src/share/vm/interpreter/linkResolver.cpp] (?)

    Or just try your luck in the HotSpot Internals forum...

  • RELEVANCY SCORE 3.87

    DB:3.87:When To Use Abstract Class Compared To Interface zz


    hi

    can some one plase advise me when to use abstract class compared to interface?

    Example will be appreciated...

    DB:3.87:When To Use Abstract Class Compared To Interface zz

    So an abstract class can carry implementation. This can be used to formulate a rule of thumb as to when to use it over an interface.

    If you have a so called type specialization relationship between the subtypes and the supertype then they're likely to benefit from shared implementation provided by the supertype, so use class (abstract or concrete) extension in this case. Type specialization is when the supertype represents a general concept like Fruit and the subtypes are specialized forms of that like Apple and Banana.

    Another common kind of relationship is called type expansion. In this case the subtypes are unlikely to have any use of implementation provided by the supertype, so use interface implementation. Type expansion is when the supertype represents a specific character the subtypes take on. For example Apple and Bicycle ure unrelated in the type specialization sense but still can share a common character like Comparable. The subtypes have been expanded to include the supertype character, namely the ability to be compared.

  • RELEVANCY SCORE 3.87

    DB:3.87:Interface And Abstract Class c3


    why we have constructor for abstract class and not for interface,

    DB:3.87:Interface And Abstract Class c3

    http://forum.java.sun.com/thread.jspa?messageID=10174604

    Double your pleasure or not!

  • RELEVANCY SCORE 3.86

    DB:3.86:Interface And Abstract Class dd


    what is the difference between interface and Abstract class?
    What are the situations we have to go for interface and Abstract class?

    DB:3.86:Interface And Abstract Class dd

    Neither an abstract class nor an interface can be instantiated (meaning you cannot create the object directly with the "new" keyword). They are both similar in that they have abstract methods. (Technically, you can create an abstract class with no abstract methods, but I would question the utility of making that class abstract in the first place).

    The two main differences are the following:

    Implementation: An abstract class can implement methods, since it is a class. An interface can never implement any methods, it only declares their signatures.Inheritance: A given class can implement an unlimited number of interfaces. A class can only extend one class. In general, I use the following rules of thumb when deciding (other developers may have differing opinions):

    Given the choice, use an interface. Since you can implement an unlimited number of interfaces, they are not as restricted, from a class hierarchy perspective. If you have several classes with the same instance (class) variables declared and several methods that all accomlplish the same thing (normally, they will even have segments of code copy-pasted between classes), then re-factor the common variables and code into an abstract class. When using interfaces, always consider delegation. Delegation is something like the following:interface IFoo {
    abstract public void bar();
    }

    public class FooDelegate {
    final public void bar() {
    // Default implementation goes here
    }
    }

    public class FooImpl implements IFoo {

    final public void bar() {
    new FooDelegate().bar();
    }
    }

    The advantage of delegation is that you can write a "helper" that contains the implementation, and then the classes that actually implement the interface can simply use the helper (e.g., delegate the implementation to another class).

    - Saish

    "My karma ran over your dogma." - Anon

  • RELEVANCY SCORE 3.86

    DB:3.86:C# Programming-Structure pz


    why a struct cannot inherit from another struct or class, and it cannot be the base of a class?
    why abstract or sealed modifiers are not permitted in a struct declaration?
    why struct types are implicitly sealed?
    How structure is a value type?
     when to use structure?

    DB:3.86:C# Programming-Structure pz

    MJ,
     
    I think the reason you can't derive from struct is that there would be no way to pass an instance of the derived struct type to a method that expects an instance of the base struct type, which is what you'd expect to be able to do.  It works for reference types because all that is passed is a reference, and references are always the same size in terms of bytes.  This is not true fo structs, which vary in size.

  • RELEVANCY SCORE 3.85

    DB:3.85:Abstract Class sj


    hello

    why cant we create an object to Abstract class and interface ?
    And if we cant create object how can we can create reference variables to both abstract and interface?

    DB:3.85:Abstract Class sj

    kirn291 wrote:
    how can we can create reference variables to both abstract and interface?I can create a variable of type List (interface), like so

    List _myList = new LinkedList();

  • RELEVANCY SCORE 3.79

    DB:3.79:Can Interface Extend Abstract Class? k3


    Can interface extend abstract class?

    I tried to make a interface extend an abstract class but i got an error stating:
    interface expected here.

    Can anyone help me ?

    DB:3.79:Can Interface Extend Abstract Class? k3

    ok, but can an interface implement an abstract class?

    No. An interface provides no implementation whatsoever. An abstract class can implement an interface, but not the other way around.

    http://java.sun.com/docs/books/tutorial/java/concepts/interface.html

    ~

  • RELEVANCY SCORE 3.78

    DB:3.78:Abstract Class Vs Interface In Term Of Speed pd


    Hi guys,
    I read every whare abstract class are faster then interface because interface require extra in direction. i want to know about how compiler deals with interface and abstract class.
    Thanks

    DB:3.78:Abstract Class Vs Interface In Term Of Speed pd

    hi,gays i think doesn't matter for code speed, we don't live in stone era. The question is what is better solution interface or abstract class.there is my visionThanks in advice

  • RELEVANCY SCORE 3.78

    DB:3.78:What Is The Main Difference B/W Interface And Abstract Class 83


    is there any specific difference b/w interface and abstract class. if wht is tht? and how?

    DB:3.78:What Is The Main Difference B/W Interface And Abstract Class 83

    abstract class can be have methods with body

    interface cannot

    interface is 100% abstract class

  • RELEVANCY SCORE 3.78

    DB:3.78:Difference Between Interface And Abstract Class 71


    I'm confused on what is the difference of implementing n abstract class and inheriting an interface?

    DB:3.78:Difference Between Interface And Abstract Class 71

    Hi,
    i want to add a few more differences --
    1.The variable defined inside an interface is public, static and final means it's basically a constant,But in case of abstract class you can hide the variable in the implementation class means you can change the value of the variable.

    One very important thing about the these two feature is when to use what?
    Ans:If a group of object is having some common property such that they are not going to be changed over a period then create an Abstract class out of that property.But if only some object is having a common property but not all then create an interface out of that property and implement all that property in Subclass.

    Thanks.

  • RELEVANCY SCORE 3.78

    DB:3.78:Abstract Class And Interface 7x


    Hi,
    This is ramana, I got a doubt
    1. I have one interface
    interface Intabs {
    abstract void method1();
    abstract void method2();
    abstract void method();

    }
    2. Iam trying to convert that interface into abstract class like below
    interface Intabs {
    abstract void method1();
    abstract void method2();
    abstract void method();

    }
    3. Again iam trying to extend that abstract class into class like below
    interface Intabs {
    abstract void method1();
    abstract void method2();
    abstract void method();

    }

    Iam getting errors

    Can i do it in multiple steps: Interface------abstract class----- class

    DB:3.78:Abstract Class And Interface 7x

    Cannot reduce the visibility of the inherited method
    from IntabsDerabst1.java
    Right. As mentioned, you can't assign weaker access priveleges to inherited methods. If you define a method as "public void foo() {}", the "foo()" method must have at least public access in all subtypes. In your example, your interface methods are public, but you're trying to give them "package-private" (default) access in the abstract and concrete implementation classes.

    ~

  • RELEVANCY SCORE 3.78

    DB:3.78:Difference Between Pure Abstract Class And Interface? 89


    hi,
    i just want to know the difference between pure abstract class(as same as interface- no implementation of methods) and interface

    Thanks,

    DB:3.78:Difference Between Pure Abstract Class And Interface? 89

    A very nice and detailed article on this code project link (posted by Magnus).

  • RELEVANCY SCORE 3.78

    DB:3.78:Diffrence Between A Interface And A Abstract Class? f7



    Hi OO ABAP Gurus

    Please clear below point to me.

    Diffrence between a Interface and a abstract class?

    Many thanks

    Sandeep Sharma..

    DB:3.78:Diffrence Between A Interface And A Abstract Class? f7


    Interface:

    All the methods of the class ARE UNDEFINED. You need to implement the interface in a class and give the method definition now. In other words INTERFACES just have the declarations no definitions.

    Abstract Class:

    All the methods which are defined for the class may have the definition or may not. Say we have 3 methods defined for this particular abstract class but only 2 have the definition and 1 does not have the definition. Then it becomes the abstract class.

    So, every Interface is a abstract class but not every abstract class is interface.

  • RELEVANCY SCORE 3.78

    DB:3.78:Development Scenario For Abstract Class And Interface In .Net ? kf


    Hi,
    In which real time Development scenario we should use abstract class or interface ???Rupesh

    DB:3.78:Development Scenario For Abstract Class And Interface In .Net ? kf

    how to transfer data in multiple Update Panel using asp.net and C#.net ?

    I have 2 update panels. Grid view is there in one update panel upd1. and text box is there in another update panel. when the link button Edit is clicked in the grid view the data need 2 come to the text box for editing.

    Rupesh

    You have to ask this last question in the ASP.NET Forums at the following address
    http://forums.asp.net/37.aspx/1?C
    Bye.Luigi Bruno - Microsoft Community Contributor 2011 Award

  • RELEVANCY SCORE 3.78

    DB:3.78:Abstract Class And Interface z1


    What is most important thing about abstract class and interface.

    When to use abstract class and interface.

    DB:3.78:Abstract Class And Interface z1

    The interface is like an agreement where the class
    which implements the interface promises to write the
    implementation code for all the functions in the
    interface.Same for an abstract class, only, rather than "all the methods" it's "all the abstract methods." Of course, you could turn around and usethat wording for interfaces too, but in that case it means "all the methods" since interfaces' methods are all abstract.

  • RELEVANCY SCORE 3.77

    DB:3.77:Abstract Class 9k



    i know the concept of abstract class in java and this concept is used in interface, i.e all the methods declared in interface are abstract. i want to know how the abtract class is different from the normal class in java

    DB:3.77:Abstract Class 9k

    all the answers you need can be found thru google: "java abstract class"

    http://java.sun.com/docs/books/tutorial/java/IandI/abstract.html

  • RELEVANCY SCORE 3.77

    DB:3.77:Abstract Class Or Interface. Which One Is Better 77


    hai everybody,

    i have a confusion between choosing of abstract class or Interface.

    abstract class Abstra
    {
    public abstract void abst();
    }
    interface Inter
    {
    public abstract void inter();
    }

    looks almost same !!!
    which one of above is better to inherit for a class.
    and more importantly why ?
    Everybody says it's interface....but i dont understand what could be the reason.
    i want to know the reason if interface is better as compare to abstract class.
    why ? why ? why ? why ?

    DB:3.77:Abstract Class Or Interface. Which One Is Better 77

    a very good answer...get to know first of all whats the difference between Abstract class and Interface.

  • RELEVANCY SCORE 3.75

    DB:3.75:Interface &Amp; Abstract Class d3


    1whats the basic difference between an interface and an abstract class?
    when should one be using an interface or an abstract class?

    2whats the difference between method overriding and method overlaoding?
    does both of them has any relation with the instance of te class implementing them?

    DB:3.75:Interface &Amp; Abstract Class d3

    http://www.google.com/search?q=java+interface+%22abstract+class%22

    http://www.google.com/search?q=java+method+overloading+overriding

  • RELEVANCY SCORE 3.75

    DB:3.75:.Net 4.0 Generic Invariance Cast Concrete Type To Base Generic Type 1x


    I am faced with the following problem:

    using System;

    using System.Collections.Generic;

    using System.Collections.ObjectModel;

    public abstract class Record { }

    public abstract class TableRecord : Record { }

    public abstract class LookupTableRecord : TableRecord { }

    public sealed class UserRecord : LookupTableRecord { }

    public abstract class DataAccessLayerTRecord : IDataAccessLayerTRecord

    where TRecord : Record, new() { }

    public abstract class TableDataAccessLayerTTableRecord : DataAccessLayerTTableRecord, ITableDataAccessLayerTTableRecord

    where TTableRecord : TableRecord, new()

    {

    #region ITableDataAccessLayerTTableRecord Members

    public void Add(TTableRecord tableRecord)

    {

    }

    public TTableRecord Get(Guid id)

    {

    return null;

    }

    public void Remove(ListTTableRecord tableRecords)

    {

    }

    #endregion

    }

    public abstract class LookupTableDataAccessLayerTLookupTableRecord : TableDataAccessLayerTLookupTableRecord, ILookupTableDataAccessLayerTLookupTableRecord

    where TLookupTableRecord : LookupTableRecord, new() { }

    public sealed class UserDataAccessLayer : LookupTableDataAccessLayerUserRecord { }

    public interface IDataAccessLayerTRecord

    where TRecord : Record { }

    public interface ITableDataAccessLayerTTableRecord : IDataAccessLayerTTableRecord

    where TTableRecord : TableRecord

    {

    void Add(TTableRecord tableRecord);

    TTableRecord Get(Guid id);

    void Remove(ListTTableRecord tableRecords);

    }

    public interface ILookupTableDataAccessLayerTLookupTableRecord : ITableDataAccessLayerTLookupTableRecord

    where TLookupTableRecord : LookupTableRecord { }

    DB:3.75:.Net 4.0 Generic Invariance Cast Concrete Type To Base Generic Type 1x

    Hi CSSS,
    I'm writing to check the issue status, does Steve's suggestion help? please feel free to let us know if you have any concern.Sincerely,
    Eric
    MSDN Subscriber Support in Forum
    If you have any feedback of our support, please contact
    msdnmg@microsoft.com.
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

    Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.

  • RELEVANCY SCORE 3.75

    DB:3.75:How To Avoid Empty Implementation In Abstract Class While Implementing An Interface? 98


    public interface IMyInterface
    {
    int A {get; set; }
    string S {get; set; }
    }
    public abstract class MyAbs : IMyInterface { }
    public class ConcreteClass : MyAbs
    { /* Implementation of IMyInterface*/ }

    Is it possible to omit the empty implementation in an abstract class as above? If so, how? why?

    DB:3.75:How To Avoid Empty Implementation In Abstract Class While Implementing An Interface? 98

    No, not possible, but in an abstract class youcan have non-abstract members (which are implemented already)
    Also, when you are overriding an abstract member just type override in the derived class and iot will show you the Member names which you can override.
    Once you will pick one, it will auitomatically create the default C# implementation in this format:
    public override void f()
    {
    throw new NotImplementedException();
    }
    So the client of this class will be thrown an exception in case they call a member which is not implemented.

    Vidya Vrat Agarwal. MCPD,MCTS, MCT, MCSD .NET, MCAD .NET, MCSD. http://dotnetpassion.blogspot,com

  • RELEVANCY SCORE 3.75

    DB:3.75:When Would You Use An Abstract Class Versus Interface ? zc


    Hi guys

    When would you guys use an Abstract Class versus and Interface ?

    Stev

    DB:3.75:When Would You Use An Abstract Class Versus Interface ? zc

    Another important distinction: declaring functions abstract in a base class not only forces the programmer to implement the function, but also allows messages to be routed to the implemented version.

    Given the shape example from before, the getArea call only works because abstract tells the compiler "hey look for a function prototype that matches this in the derived class"

  • RELEVANCY SCORE 3.72

    DB:3.72:Abstract Class And Interface 33


    When we have got is the interface then do you need is an abstract class? ....since i can divide an abstract class to two one is interface and the other a concrete class.....So where is the exact functionality of an abstract class.
    Why is that a file name should be the same as that of the public class declared in that file?

    DB:3.72:Abstract Class And Interface 33

    Why is that a file name should be the same as that of the public class declared in that file?Because that's what is required by the JVM.

  • RELEVANCY SCORE 3.72

    DB:3.72:What Is The Difference Between Abstract And Interface? zd


    Could some one explain what is the difference between abstract class and interface class.

    Lets say I'm creating class why would I choose abstract over interface?

    THanks.

    DB:3.72:What Is The Difference Between Abstract And Interface? zd

    The difference between abstract classes and interfaces is interfaces are defined methods only. In abstract class methods are derived.

  • RELEVANCY SCORE 3.72

    DB:3.72:What Is An Interface &Amp; Abstract Class ? zm


    hi ,
    i am new to java,
    pls give the answer for this question,

    what is an interface abstract class ?
    why we go for interfaces and abstract classes?

  • RELEVANCY SCORE 3.72

    DB:3.72:Constrained Generics Method Overload Inference 8s


    Hello,Let's have this set-up:

    public abstract class MyBaseClass { }  

     

    public sealed class Class1 : MyBaseClass  

    {  

       public string PropertyA;  

    }  

     

    public sealed class Class2 : MyBaseClass  

    {  

       public string PropertyB;  

    DB:3.72:Constrained Generics Method Overload Inference 8s

    Good point =)  But you have to give the C# compiler a break here, it has long since compiled the code and done it's bit - there are no C++ templates here.  This is the runtime's 'mischief' - forming complete types - and following the ECMA for overloading with generics ;)   Cheers,Dave

  • RELEVANCY SCORE 3.71

    DB:3.71:Difference % Abstract Class And Interface? d3


    Hi,

    I am confused about abstract class and interface. For interface, the subclass has to implement all the parent class methods. But, it is no need in abstract class.

    However, in which situation should I use abstract class or interface?

    Thanks for explanation.

  • RELEVANCY SCORE 3.67

    DB:3.67:Re: Why An Interface Is Used In A Java Program pc


    These are fair comments as per as interface is concern.... we need interface to declare the methods without implementing the methods. Basically interfaces help implementing classes in a organised way.
    Now We got abstract class also, which has got more or less same features like interfaces. In abstract class also we can declare a method without implementation.
    If we use abstract class and extend that abstract class, we don't have implement all the abstract methods in that particular class,which would extend the abstract class, but if we implement an interface in a class, we have to define all the methods with their body. Now, can anyone tell me , in a generic way, when do we use interface and when do we use abstract class. I don't need the differences between abstract class and interface...that i know...thanks in advance
    take it easy
    RD
    l

    DB:3.67:Re: Why An Interface Is Used In A Java Program pc

    For Ex: 5 years down the line, .........I always wondered why it is said "down the
    line" and not up the line.
    What's so downish about the future ?People degrade as the years pass by. :P

  • RELEVANCY SCORE 3.67

    DB:3.67:Adding Preconditions In Inherited Interface jx


    I see I can add preconditions in inherited interface to methods of base interface. I think this is a bug and checker should prevents me from doing this as it prevents me from adding preconditions to implemented interface methods or overrided methods.
    [ContractClass(typeof(IFooContract))]
    public interface IFoo
    {
    void Do(string s);
    }

    [ContractClassFor(typeof(IFoo))]
    internal abstract class IFooContract : IFoo
    {
    private IFooContract()
    {
    }

    void IFoo.Do(string s)
    {
    Contract.Requires(s != null);
    }
    }

    [ContractClass(typeof(IBarContract))]
    public interface IBar : IFoo
    {
    }

    [ContractClassFor(typeof(IBar))]
    internal sealed class IBarContract : IBar
    {
    private IBarContract()
    {
    }

    void IFoo.Do(string s)
    {
    // Checker should report warning here:
    Contract.Requires(!string.IsNullOrEmpty(s));
    }
    }

    And the second question: why checker enforces ContractClass for class be abstract class while ContractClass for interface can be concrete class?

    DB:3.67:Adding Preconditions In Inherited Interface jx

    I see what you mean about the stronger postconditions, but really the Do method is still IFoo's Do method. Interface inheritance is just the union of all the interface methods, not overriding as in class inheritance. So I'm not sure that makes sense to allow.Yes, I guess we could also require the contract class for interfaces to be abstract. We just hadn't thoughtof it. I'll add that to our work list.Thanks!

  • RELEVANCY SCORE 3.65

    DB:3.65:Difference B/W Abstract &Amp; Interface dx


    Anyone tell me 4 difference b/w abstract class and interface
    plz help me

    DB:3.65:Difference B/W Abstract &Amp; Interface dx

    Asking once is enough.
    http://forum.java.sun.com/thread.jspa?threadID=734361

  • RELEVANCY SCORE 3.64

    DB:3.64:Difference B/W Abstract Class And Interface mf


    Hi,
    can anyone tell the difference between Abstract class and an Interface?

    Thanks in advance!

    DB:3.64:Difference B/W Abstract Class And Interface mf

    The majoor diiffernce is that Interface canot ber
    inherited while absract calss can be inherited
    one abract class can iheret other abstract class
    while Interface doesnot???

  • RELEVANCY SCORE 3.64

    DB:3.64:Regarding The Abstract And Interface km


    hai,
    I am new to java programming

    I want to difference between abstract interface,interface and abstract class

    public abstract interface Test{}

    public interface Test{}

    public abstract class Test{}

    which kind of situations use the above interfaces and abstract classes

    It would be helpfull if explain with example....

    Thanks

    DB:3.64:Regarding The Abstract And Interface km

    shashikumar, please don't multipost and don't use the browser's back button to edit your post. This creates multiple posts. I've removed the other thread you started a minute after this one.

    db

  • RELEVANCY SCORE 3.64

    DB:3.64:Abstract Class Vs Interface ? 9d


    hi all,

    can anybody help me.

    if i have an abstract class (full of abstract method definitions) and an interface(having same definitions).

    Now the question is in which situation we go for an ABSTRACT CLASS with full of abstract method definitions and in which situation we go for an INTERFACE.

    and other differences between ABSTRACT CLASSES and INTERFACES except Multiple Inheritence ?

    DB:3.64:Abstract Class Vs Interface ? 9d

    Hi,
    All the variable inside the interface are static and final(You can't change it).While in case of abstract class it is not so. And in abstract class you can have concrete method also while in interface all the method must be non concrete So its depends on your requirement.

    Regards,
    Alok

  • RELEVANCY SCORE 3.62

    DB:3.62:Difference Between An Interface And An Abstract Class 9f


    Hey:

    I'm curious, what's the difference between an interface and an abstract class? Thanks.

    DB:3.62:Difference Between An Interface And An Abstract Class 9f

    "You have an abstract class if you want to implement some of the methods in it, but you do not want users to make instances of the class or do not want to implement all of the methods. Take a look at some of the abstract classes in java.util. Nearly all of the methods are implemented already so that it's far easier to create new data structures than if only interfaces were provided. "

    That's what I was looking for. Thanks.

  • RELEVANCY SCORE 3.62

    DB:3.62:Simple Query ac


    Difference between Abstract class and interface with practical example

    DB:3.62:Simple Query ac

    You are right; it was a simple query. (and I don't mean "simple" as in lacking complexity.)

  • RELEVANCY SCORE 3.61

    DB:3.61:Oops Topic List kc


    Hi all,
    I want to just cover the entireoops topic list, I have prepared as per I know if any topicwhich Ihave miss please add.
    Class
    Object
    Inheritance
    Abstraction
    Encapsulation
    Polymorphism
    Association
    Aggregation
    Abstract class and methods
    Virtual class and methods
    Static class and methods
    Sealed class and methods
    Generic class and methods
    Partial class and methods
    Interface
    Delegate
    Events
    Shadowing
    Access modifiers
    Overriding
    Overloading
    Constructor(private, public, static)
    Boxing and un boxing
    Value type and reference type

    DB:3.61:Oops Topic List kc

    Hi Ravi,
    Do you have any question about C#?
    Here is an anticle about OOP in MSDN:http://msdn.microsoft.com/en-us/library/dd460654.aspxWe are trying to better understand customer views on social support experience, so your participation in this interview project would be greatly appreciated if you have time. Thanks for helping make community forums a great place.

    Click
    HERE to participate the survey.

  • RELEVANCY SCORE 3.61

    DB:3.61:Difference B/W Abstract Class And Interface dx


    hi friends,

    can anyone plz divulge the differences between abstract class and interface and under what situations can we use these concepts.

    thanks

    madhusudan.D

  • RELEVANCY SCORE 3.61

    DB:3.61:Abstract Class Or Inteface 89


    Pls give me some practical example of choosing among abstract class and interface.

    DB:3.61:Abstract Class Or Inteface 89

    Search these forums using the box on the left. This question is asked about 50 times a week, there are tons of answers around

  • RELEVANCY SCORE 3.60

    DB:3.60:Diff. Between Interface And Abstract Class 3s


    hi,
    Can any one tell me about diff between interface and abstract class in practical way.advanced thanks for ur response.
    -PVMVS

    DB:3.60:Diff. Between Interface And Abstract Class 3s

    This question gets asked all the time. I found lots of hits by searching this forum with the words: interface abstract class difference

    I'm sure google will return even more. Searching existing posts should always be done before posting.

  • RELEVANCY SCORE 3.60

    DB:3.60:C#.Net Difference Between Abstract Class And Sealed Class df


    Hi Experts, What is Difference Between Abstract Class And Sealed Class in C#? Thanks.

    Knowledge Shared Is Knowledge Gained

    DB:3.60:C#.Net Difference Between Abstract Class And Sealed Class df

    Hi Geert van Horrik, Thanks.Knowledge Shared Is Knowledge Gained

  • RELEVANCY SCORE 3.58

    DB:3.58:Difference Between Interface And Abstract Class? x1


    Hi,

    Can u plz explain
    at what scenarios we use interface and abstract class.?

    Thanks,
    B.Maruthi

    DB:3.58:Difference Between Interface And Abstract Class? x1

    If you had read the FAQ at the top of the forum home
    page you wouldn'y have bothered to ask this
    question.Anyways heres the link

    Read the question number 13 in this link

    http://access1.sun.com/FAQSets/newtojavatechfaq.htmlnice

  • RELEVANCY SCORE 3.58

    DB:3.58:Generic Object Structure Question x1


    Hello,
    I think I've been looking at this problem too long and have developed tunnel vision. I have the following object structure:
    public interface IPersistable
    {
    some property prop{get;set;}
    some eventsome type ErrorEvent;
    }
    public interface IEndPointT where T:IPersistable
    {
    void Write(T object);
    T Read();
    }
    public abstract class EndPointT:IEndPointT where T:IPersistable
    {
    public abstract void Write(T object);
    public abstract T Read();
    public abstract void Begin();
    public abstract void Finish();
    public abstract void Reset();
    }
    public class FileEndPointT:EndPointT where T:IPersistable
    {
    public FileEndPoint(){}
    //generic implementation of abstract class
    }
    public sealed class SpecificFileSystemEndPoint:FileEndPointIPersistable
    {
    public SpecificFileSystemEndPoint(){}
    //specialized implementation
    }

    My problem is this, when unit testing, I need to call an object with the following line:
    FileEndPointT endpoint = new SpecificFileSystemEndPoint();
    I get a compiler error telling me that the implicit conversion can not be made. I'm sure it's silly, and I'm overlooking something really obvious. If someone could help point it out for me that would be awesome.

    Thanks in advance.

    JP

    DB:3.58:Generic Object Structure Question x1

    Thank you Michael.
    Yes, I only wrote out method stubs for the sake of the example, as it was more of a structural based question; I didn't want to waste the readers time lol. I do agree with your observation on having abstracted too far, however. Thank you for
    that.
    In this snippet, the endpoint could be persisting data to the file system, to a dbserver, or giving it to a web service (given a particular type, all three instances would be receiving the same data, just through a different mechanism). But you're
    right, 'EndPoint' may have been too confusing a name for that object.
    Anyway, thank your for your attention and insights. Much appreciated.
    JP

  • RELEVANCY SCORE 3.57

    DB:3.57:Lookup Of Extension Methods - C# Compiler (Vs 2010) Reports Errrors (Partly Non-Deterministically) mp


    Hello,
    I think I stumbled over a C# compiler bug. Interestingly, partly the errors are reported on an irregular basis!
    I tried to boil down the problem to a minimum of LOC but it is stilla little bit lengthy... sorry...
    File Program.cs:

    namespace GenericInferenceError
    {
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Collections;

    using GenericInferenceError.This;
    using GenericInferenceError.That;

    public interface ICollection
    {
    }

    internal interface ICollection2 : ICollection
    {
    }

    public interface IItem
    {
    }

    public interface IPart
    {
    }

    public class Project
    {
    public C GetC()
    where C : class, ICollection, new()
    {
    return new C();
    }
    }

    public abstract class CollectionA, B : ICollection2, IEnumerableA
    where A : ItemA, B
    where B : PartA, B
    {
    private ListA list = new ListA();

    public IEnumeratorA GetEnumerator()
    {
    return this.list.GetEnumerator();
    }

    IEnumerator IEnumerable.GetEnumerator()
    {
    return this.GetEnumerator();
    }
    }

    public abstract class ItemA, B : IItem
    where A : ItemA, B
    where B : PartA, B
    {
    public IEnumerableB Parts { get; set; }
    }

    public abstract class PartA, B: IPart
    where A : ItemA, B
    where B : PartA, B
    {
    }

    public static class ItemExtension
    {
    public static IEnumerableB GetPartsA, B(this IEnumerableItemA, B items)
    where A : ItemA, B
    where B : PartA, B
    {
    return items.SelectMany(item = item.Parts);
    }
    }

    public static class Program
    {
    static void Main(string[] args)
    {
    var project = new Project();

    var thisParts = project.GetThisCollection().GetParts();
    var thatParts = project.GetThatCollection().GetParts();
    }
    }
    }

    File This.cs:
    namespace GenericInferenceError.This
    {
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;

    public sealed class ThisCollection : CollectionThisItem, ThisPart
    {
    }

    public sealed class ThisItem : ItemThisItem, ThisPart
    {
    }

    public sealed class ThisPart : PartThisItem, ThisPart
    {
    }
    }

    File That.cs:
    namespace GenericInferenceError.That
    {
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;

    public sealed class ThatCollection : CollectionThatItem, ThatPart
    {
    }

    public sealed class ThatItem : ItemThatItem, ThatPart
    {
    }

    public sealed class ThatPart : PartThatItem, ThatPart
    {
    }
    }

    From time to time, especially after switching between solution platforms (x86, x64, and AnyCPU) the compiler reports (one or both lines):
    Error1'GenericInferenceError.This.ThisCollection' does not contain a definition for 'GetParts' and no extension method 'GetParts' accepting a first argument of type 'GenericInferenceError.This.ThisCollection' could be found (are you missing a
    using directive or an assembly reference?)D:\Projects\GenericInferenceError\Program.cs8223GenericInferenceError
    Error2'GenericInferenceError.That.ThatCollection' does not contain a definition for 'GetParts' and no extension method 'GetParts' accepting a first argument of type 'GenericInferenceError.That.ThatCollection' could be found (are you missing a using
    directive or an assembly reference?)D:\Projects\GenericInferenceError\Program.cs8323GenericInferenceError
    In the real project there are lines where this error is reported always, but I cannot reproduce it in the small project.
    Remarkebly, changing ONE of the lines, e.g.
    var thisParts = (project.GetThisCollection() as IEnumerableThisItem).GetParts();
    leads to compiler-silence: the other line is not marked as error any more.

    Basically I think there is a very strange bug inthe extension lookup algorithm.
    No need to say that the extension methods are never shown by IntelliSense.

    Kind regards

    DB:3.57:Lookup Of Extension Methods - C# Compiler (Vs 2010) Reports Errrors (Partly Non-Deterministically) mp

    I would report it as bug at Microsoft Connect but it is VS 2010, so one is redirected here...!?

  • RELEVANCY SCORE 3.57

    DB:3.57:Abstract Class Or Interface ? 11


    can any one tell me the difference between an abstract class an an interface. which is more useful ?

    DB:3.57:Abstract Class Or Interface ? 11

    You could also try searching this site for your question. It has been discussed in other threads as well (I posted a simialar (how do you spell that?) question).

  • RELEVANCY SCORE 3.57

    DB:3.57:Who Can Tell The Difference Of The Abstract Interface Class? 79


    someone ask me that he had a abstarct interface class, such as :
    public abstract interface Book{
    }
    I was comfused, who can tell me why use it?

    DB:3.57:Who Can Tell The Difference Of The Abstract Interface Class? 79

    http://java.sun.com/docs/books/tutorial/java/interpack/interfaceDef.html

    Scroll down to the bottom.

    Drake

  • RELEVANCY SCORE 3.57

    DB:3.57:Dificult To Understand Interface And Abstract Class 98


    - I need explain what is better to use, interface or abstract class to inherit of square/rectangle.
    Example included is appreciated. Thanks.

    DB:3.57:Dificult To Understand Interface And Abstract Class 98

    Thank you for help me.
    Do you have a classe de rectangle and square?

  • RELEVANCY SCORE 3.57

    DB:3.57:How To In Repository Pattern Get Insert Id 9c


    hi
    i use from repository pattern below like , this is correct and just i have a problem for get insert row id (identity id)
    in model class:
    public interface IEntityT
    {
    T Id { get; set; }
    }
    public abstract class BaseEntity
    {

    }

    public abstract class EntityT : BaseEntity, IEntityT
    {
    public virtual T Id { get; set; }
    }public class Country : Entityint { [Required] [MaxLength(100)] [Display(Name = Country Name)] public string Name { get; set; }
    in Repository class
    public interface IGenericRepositoryT where T : BaseEntity
    {
    T Add(T entity);
    void Save();
    }
    public abstract class GenericRepositoryT : IGenericRepositoryT
    where T : BaseEntity
    {
    protected DbContext _entities;
    protected readonly IDbSetT _dbset;

    public GenericRepository(DbContext context)
    {
    _entities = context;
    _dbset = context.SetT();
    }
    }
    public virtual T Add(T entity)
    {

    return _dbset.Add(entity);
    }
    public virtual void Save()
    {
    _entities.SaveChanges();
    }
    public interface IUnitOfWork : IDisposable
    { int Commit();
    }
    public sealed class UnitOfWork : IUnitOfWork
    {
    private DbContext _dbContext;
    public UnitOfWork(DbContext context)
    {
    _dbContext = context;
    }
    public int Commit()
    {
    // Save changes with the default options
    return _dbContext.SaveChanges();;
    }
    }
    public interface ICountryRepository : IGenericRepositoryCountry
    {
    Country GetById(int id);
    }
    public class CountryRepository : GenericRepositoryCountry, ICountryRepository
    {
    public CountryRepository(DbContext context)
    : base(context)
    {
    }
    public Country GetById(int id)
    {
    return FindBy(x = x.Id == id).FirstOrDefault();
    }
    }
    and in Service class:
    public interface IService
    {
    }
    public interface IEntityServiceT : IService
    where T : BaseEntity
    {
    void Create(T entity);
    }
    public abstract class EntityServiceT : IEntityServiceT where T : BaseEntity
    {
    IUnitOfWork _unitOfWork;
    IGenericRepositoryT _repository;

    public EntityService(IUnitOfWork unitOfWork, IGenericRepositoryT repository)
    {
    _unitOfWork = unitOfWork;
    _repository = repository;
    }
    public virtual void Create(T entity)
    {
    if (entity == null)
    {
    throw new ArgumentNullException(entity);
    }
    _repository.Add(entity);
    var id= _unitOfWork.Commit();
    }
    }
    public interface ICountryService : IEntityServiceCountry
    {
    Country GetById(int Id);
    }
    public class CountryService : EntityServiceCountry, ICountryService
    {
    IUnitOfWork _unitOfWork;
    ICountryRepository _countryRepository;

    public CountryService(IUnitOfWork unitOfWork, ICountryRepository countryRepository)
    : base(unitOfWork, countryRepository)
    {
    _unitOfWork = unitOfWork;
    _countryRepository = countryRepository;
    }

    public Country GetById(int Id)
    {
    return _countryRepository.GetById(Id);
    }
    }
    and in test class
    _CountryService.Create(country);
    now how to get Identity id after insert
    please help me thanks

  • RELEVANCY SCORE 3.57

    DB:3.57:Abstact Class And Interface s9


    Hi,

    Any One Can Let me know the exact diff. Between the Abstract class and Interface.

    With
    BAbu

  • RELEVANCY SCORE 3.57

    DB:3.57:Abstract Class And Interface 17



    Please tell me what is Abstract Class and Interface. Please explain with help of simple example and also tell me difference between them.

    DB:3.57:Abstract Class And Interface 17


    hi

    i will suggest u to refer some basic java book , to clear ur basic concept of OOPS , because these principal remain same for all languages that follow OOPS concept .

    and under standing these with java is easier then with ABAP .

    Abstract Class

    class which have atleast 1 method which is declared only , (no definition is given for it in this class is mentioned as Abstract Method )

    and that class is defined as Abstract class

    Interface :

    only declaration of method done here , no method will be defined here , class which will implement this interface will give definition .

    Diff. b/w Abstract Class and Interface :

    ABS Class can have method with there definition , but one method should be there with declartion only.

    Interface will have all method with out definition .

    hpoe this help u .

    reward if helpful.

  • RELEVANCY SCORE 3.57

    DB:3.57:Diference Between Abstract Class And Interface cp



     
    Hi,
     
    I had a doubt on basic concept of interface and abstract class.
     
    I had idea of wht is interface and abstract class but there is case ,can any do justification on these case is
     
    Abstract class is a clas where some methods r defined and some are abstract methods.
    Interface is where all methods are abstract .
     
    but what happen if i try to maintaince all methods in abstract class as abstract which is equivalent to interface.?
     
    We go for abstract class if want to extend functionality of class.For interface if we wanna implement a new implementation.
     
    is there any other difference apart from this and other issues if we try to have all methods abstract .
     
     
    With regards
    Mahender

    DB:3.57:Diference Between Abstract Class And Interface cp

    Hi,
     
    Thnx for giving info.Actually iam looking for projct development point of view..In whihc cases i do go 4 developing abstract classes  other interfaces

  • RELEVANCY SCORE 3.57

    DB:3.57:Mdb Abstract Base Class And Ejb3 Annotations 1k



    I have following scenario where my MDB class extends an abstract class which implements the MessageListener interface.
    public abstract class MDBBase implements MessageListener {
    public void onMessage(Message message) {
    ....
    processJob(some-params)
    }
    public abstract void processJob (some-params);
    }

    public class MyMDB extends MDBBase {
    public abstract void processJob (some-params) {

    }
    }

    DB:3.57:Mdb Abstract Base Class And Ejb3 Annotations 1k


    I have following scenario where my MDB class extends an abstract class which implements the MessageListener interface.
    public abstract class MDBBase implements MessageListener {
    public void onMessage(Message message) {
    ....
    processJob(some-params)
    }
    public abstract void processJob (some-params);
    }

    public class MyMDB extends MDBBase {
    public abstract void processJob (some-params) {

    }
    }

  • RELEVANCY SCORE 3.57

    DB:3.57:Abstract Class And Interface 7s


    Hai,

    I want to know In which suituation i want to use abstract class and Interface in My Project

    Regards,
    John Jayaraj,
    +91 9865315105

    DB:3.57:Abstract Class And Interface 7s

    Use abstract classes when you need to evolve a hierarchy from a class with some hard coded methods and parameters that must be available for all it's subclasses, and when you don't need to use polymorphism :

    abstract class Papapa() {
    public SomeType somethingI;
    public SomeType somethingII;

    abstract public void methodI(); // must be implemented at subclasses
    abstract public void methodII();
    public void methodAvaiableForAllClasses() {
    do something;
    // you can call methodI and methodII here
    }
    }

    abstract classes also lets you define global variables to be used (i heard its faster than interfaces too, but I don't know enough about it to confirm).

    Interfaces in the other way around lets you play with polymorphism.

    class XXX implements YYY, ZZZ.
    Remember that in Java you can only extends one class (abstract or not).
    class XXX extends YYY, ZZZ would result in an error.

    A good way to get the felling where to use abstract classes and interfaces is reading the Collection API source code.

  • RELEVANCY SCORE 3.57

    DB:3.57:Re: Difference Between Abstract Class And Interface. f3


    Thanks, jverd. I have got it.

    George

  • RELEVANCY SCORE 3.57

    DB:3.57:Why Interface Is More Preferable Than Abstract Class p9


    I am practicing java programming. I need your help.
    please any one tell me "Why interface is more preferable than abstract class".

    Thanks;

    skumar

    DB:3.57:Why Interface Is More Preferable Than Abstract Class p9

    Double-post
    http://forum.java.sun.com/thread.jspa?threadID=643081

  • RELEVANCY SCORE 3.57

    DB:3.57:Help With Interface And Abstract cs


    Hi all

    what is the difference between an interface and an abstract class??

  • RELEVANCY SCORE 3.57

    DB:3.57:Abstract Class Needs To Implement Interface ms


    Hello, I have an interface and base abstract class defined as follows: interface IbusinessInterface{    void DoSth1();    void DoSth2();    void DoSth3();    void DoSth4();    void DoSth5();    ...    ...    void DoSthN();}public abstract class BaseClass : IBusinessInterface{    public abstract void DoSth1();    public abstract void DoSth2();    public abstract void DoSth3();    public abstract void DoSth4();    public abstract void DoSth5();    ...    ...    public abstract void DoSthN();} what is the reason that this abstract class needs to have methods of the interface implemented  ?Thanks, Michal

    DB:3.57:Abstract Class Needs To Implement Interface ms

    Look at the other side of the coin!  Think interface contract.  The abstract base class is NOT defining any default implementation for you.  Now, when you browse the abstract class you can SEE the member methods that are or not implemented without having to look any further.  Also, when the members of the abstract class are declared as abstract the IDE can generate method stubs for you automatically!  That does not happen if they are declared as virtual.

    Mark the best replies as answers. Fooling computers since 1971.

  • RELEVANCY SCORE 3.57

    DB:3.57:Core Java 83


    what is differernce between abstract class and interface?

    DB:3.57:Core Java 83

    jwenting wrote:
    maybe an attempt at counting only posts which make any kind of sense at all?Where did the '1' come from then?

  • RELEVANCY SCORE 3.57

    DB:3.57:Interface And Abstract Class ad


    Why can't we declare a static method in Interface but it's possible in abstract class?

    DB:3.57:Interface And Abstract Class ad

    Because an interface is simpler than an abstract class.
    Normally you would put a static method like this into a utility class with a private constructor. see the Math class.

  • RELEVANCY SCORE 3.55

    DB:3.55:Java Interfaces And Abstract Classed fc


    what is the difference between interface and abstract class?

    DB:3.55:Java Interfaces And Abstract Classed fc

    I suggest you try writing some code and see.

  • RELEVANCY SCORE 3.55

    DB:3.55:What Is The Different Between Abstract An Interface Class? jf


    what is the different between abstract an interface class?
    and
    What is the different between access specifier of public and friendly.

    DB:3.55:What Is The Different Between Abstract An Interface Class? jf

    what is the different between abstract an interface
    class?interfaces contain only signatures of method you'll have to implement and constant
    whereas abstract classes contains method implemented and/or method non implemented

    What is the different between access specifier of
    public and friendly.the scope of 'friendly' is the package which contains it

  • RELEVANCY SCORE 3.55

    DB:3.55:Possible Modifiers For Interface Inside Class, Interface Inside Interface 8m


    what are the possible modifiers for a interface inside interface,
    interface inside class,
    a. abstract
    b. extends
    c. final
    d. private
    e. protected
    f. public

  • RELEVANCY SCORE 3.55

    DB:3.55:Who Can Tell The Difference Of The Abstract Interface Class? xf


    someone ask me that he had a abstarct interface class, such as :
    public abstract interface Book{
    }
    I was comfused, who can tell me why use it?

    DB:3.55:Who Can Tell The Difference Of The Abstract Interface Class? xf

    Cross post - http://forum.java.sun.com/thread.jspa?threadID=694601tstart=0

  • RELEVANCY SCORE 3.55

    DB:3.55:Abstract Class And Interface???? ja


    hi all, i would like to know the difference between abstract class and interface....could anybody enlighten me on this....

    DB:3.55:Abstract Class And Interface???? ja

    search the forums, lot's of times answered this one has been.

  • RELEVANCY SCORE 3.55

    DB:3.55:Difference ???? xz


    What's the difference between an Interface and Abstract class ??????

    DB:3.55:Difference ???? xz

    Is google broken again?
    [http://www.google.co.uk/search?q=What's+the+difference+between+an+Interface+and+Abstract+class] 652,000 hits

  • RELEVANCY SCORE 3.55

    DB:3.55:Diff Between Interface And Abstract Class 9a



    Hi to all,

    I am woking on OOP in ABAP .Could any one can tell the difference between interface and abstract class.

    thanks in advance .

    DB:3.55:Diff Between Interface And Abstract Class 9a


    Hello Sagar,

    like Uwe told one basic difference is that you may provide some methods with an abstract class but not with an interface. The unique feature of interfaces is that you may implement several ones while abstract classes are limited to one inheritance hierarchy.

    Regards

    Klaus

  • RELEVANCY SCORE 3.55

    DB:3.55:Partnotdiscoverableattribute Is Not Inherited z1


    Hi everyone,
    Why isn't PartNotDiscoverableAttribute inherited?
    Was there simply no good use cases for it or is there some deeper infrastructure-related issue that prevents it?
    Is there an alternative that I'm missing? (Otherthan my current workaround for this limitation, as described below.)
    I'm in a situation where I'd really like to useInheritedExportAttribute, butunfortunately I cannot becauseI can't mark intermediate classes within my inheritance hierarchy with
    PartNotDiscoverableAttribute.
    Consider the following type hierarchy.

    [InheritedExport]
    interface IOneTimeInitialization { }

    [PartNotDiscoverable]
    interface IDevice : IOneTimeInitialization { }

    abstract class DeviceProvider : ProviderBase, IDevice { }

    abstract class ScannerProvider : DeviceProvider
    {
    [Export]
    private static readonly IOneTimeInitialization export = GetDefaultProvider();
    }

    sealed class ConcreteScannerProvider : ScannerProvider { }

    DB:3.55:Partnotdiscoverableattribute Is Not Inherited z1

    Hi,
    BTW, I'm using MEFfor .NET 3.5 downloaded from CodePlex, although it seems the same issue is present in the .NET 4.0 FCL as well.
    - Davehttp://davesexton.com/blog

  • RELEVANCY SCORE 3.55

    DB:3.55:Codetypedeclaration -- A Static Class 3m


    I've been trying to generate a static class using CodeTypeDeclaration class, however, there is no such option to set in its TypeAttributes property. A static class, as we can see in ILDASM, is basically abstract + sealed. If I replacepublic static class MyClassbypublic abstract sealed class MyClassI get an error an abstract class cannot be sealed or static. There is a workaround to generate a sealed class with a private constructor, but still, any idea how to generate a static class? Thank you in advance!!!

    DB:3.55:Codetypedeclaration -- A Static Class 3m

    Put another way, the CodeDom wont let you do this because most languages wont let you do that.  Prior to C# 2.0, you could not create an abstract sealed class.  Now you can do it with the static keyword, but you still can't with the abstract/sealed keywords.  Since the primary purpose of the Code DOM is model high-level code, it makes sense that the Code DOM would not allow this.
     

  • RELEVANCY SCORE 3.54

    DB:3.54:Abstract Class Cannot Be Override From An Interface Class sd


    Please help:(
    how to make an existing class to be abstract, so that it can override from an interface class?

    DB:3.54:Abstract Class Cannot Be Override From An Interface Class sd

    In my previous post, I implemented the isLargerThan(Relatable other) method as an example*.
    After a few searches, I've finally found out what you need : [*Implementing an Interface*|http://v1.dione.zcu.cz/java/docs/tutorial/java/IandI/usinginterface.html] .
    You don't have to include the lines of my example to the lines of the tutorial example.

    Edit : My sight is a real problem. I didn't notice you posted the tutorial example.

    Edited by: Chicon on Sep 20, 2009 10:21 AM

  • RELEVANCY SCORE 3.54

    DB:3.54:Get The Class And Methods Name Of An Abstract Sealed Class p3


    How do I get the class and methods name of an abstract sealed class? Any help will be greatly appreciated.

    DB:3.54:Get The Class And Methods Name Of An Abstract Sealed Class p3


    I disagree. It is possible to make an abstract sealed class in the c cli. Example:
    public ref class MyClass abstract sealed
    {
    ________
    __________
    };

    In most languages, this is what is typically called a static class. (For example, in C#, you can't declare abstract sealed - the compiler enforces this, but if you declare a class static, you get this in IL. Same with a VB Module. ) C/CLI
    is the only language where you can declare it like this, and you weren't saying you were using it - hence my comment.
    It's a class you can't create instances of - and will only contain static members.
    If you're working in C/CLI, an abstract sealed class will only have static method declarations, and no instance method declarations. You can still use Type.GetMethods, but you'll want to use BindingFlags.Static to retrieve them.

    You'd get this, in C/CLI, via:
    // Get the Type handle for your class
    Type^ myType = YourClass::typeid;

    // Get the public (static) methods.
    arrayMethodInfo^^methods = myType-GetMethods( static_castBindingFlags(BindingFlags::Public | BindingFlags::Static) );

    for each (MethodInfo^ mi in methods)
    Console::WriteLine(mi-Name);

    Reed Copsey, Jr. - http://reedcopsey.com
    If a post answers your question, please click Mark As Answer on that post and Mark as Helpful.

  • RELEVANCY SCORE 3.53

    DB:3.53:Difference Between Interface And Abstract Class a1


    Hi sirs,

    Give me the differences between interface and abstract class
    and when we go for interfaces and abstract class in developing an application

    DB:3.53:Difference Between Interface And Abstract Class a1

    An interface is a 100% abstract class, which means it doesn't contain any code, just method names and signatures. You use abstract classes when you want some code to be shared among the inheritors.

    The advantage with interface is that a class can implement as many interfaces as you like, while it can only extend one (abstract) class.

    So, you use interfaces when you need to extend other classes or doesn't want any code shared, and abstract classes when you don't want to extend other classes, and would like to share some code.