• RELEVANCY SCORE 6.05

    DB:6.05:Abstract Class 13




    Difference between abstract class and interface
    use of abstract class

    DB:6.05: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 5.48

    DB:5.48: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:5.48: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 5.37

    DB:5.37:Abstract Classes m9




    can all classes inherit Abstract class....or is there any restriction that only one class can inherit abstract class

    DB:5.37:Abstract Classes m9

    An interface says what an object has to do.

    A class says how to do it. The class might be abstract, which means that it only says how to do some of it -- a subclass then has to say how to do the rest.

  • RELEVANCY SCORE 5.29

    DB:5.29:Abstract Classes a7


    Is it possible for an abstract class to have both abstract methods and non-abstract methods?

    public abstract class Person
    {
    private String name;

    public Person(String n)
    { name = n;}

    public String getName()
    {return name;}

    public abstract String getAddress();

    }And can a non-abstract class have abstract methods?

    DB:5.29:Abstract Classes a7

    An abstract class can have both abstract methods and non abstract method i,e the regular methods , but a non abstract class cannot have abstract methods. from this what we get is that its a must to have the class as abstract whenever you have a abstract method in it.

    if u add an abstract method in a simple class it will throw a error saying that u can only define an abstract metod in an abstract class.

  • RELEVANCY SCORE 5.29

    DB:5.29:Abstract Class 71


    Hi,
    can u tell me the exact difference between abstract class and interface.under which situations we should use this.

    DB:5.29:Abstract Class 71

    AmitChalwade123456 wrote:
    Anumanick wrote:
    Hi,
    can u tell me the exact difference between abstract class and interface.under which situations we should use this.A class implementing an interface must implement all of the methods defined in the interfacepublic abstract class ImNotImplementingThat implements Runnable {

    // public void run() {} I was going to implement this, but I can't be bothered

    }while a class extending an abstract class need not implement any of the methods defined in the abstract class. public class WhyAreYouMoaningAboutRead extends java.io.InputStream {

    // I won't compile, because I'm not implementing the abstract void method 'read'

    }Additionally, a class extending an abstract class can implement an infinite number of it's own methods.Erm

    An abstract class can contain non-abstract methods which do not have to be overridden in the subclass.Indeed

  • RELEVANCY SCORE 5.29

    DB:5.29:Access Overriden Method Of An Abstract Class za


    class Abstract
    {
    abstract void abstractMethod(); //Abstract Method
    void get()
    {
    System.out.print("Hello");
    }
    }

    class Subclass extends Abstract
    {
    void abstractMethod()
    {
    System.out.print("Abstract Method implementation");
    }
    void get()
    {
    System.out.print("Hiiii");
    }
    }

    In the above code, i have an abstract class called "Abstract", which has an abstract method named "abstractMethod()" and another method called "get()".
    Now, this class is extended by "Subclass", it provides implementation for "abstractMethod()", and also overrides the "get()" method.
    Now my problem is that i want to access the "get()" method of "Abstract" class. Since it is an abstract class, i cant create an object of it directly, and if i create an object like this:
    Abstract obj = new Subclass();

    then, obj.get() will call the get() method of Subclass, but how do i call the get() method of Abstract class.
    Thanks in advance

    DB:5.29:Access Overriden Method Of An Abstract Class za

    hey thanks a lot,, i have another doubt regarding Abstract classes.
    i was just trying something, in the process, i noticed that i created an abstract class which does not have any abstract method, it gave no compilation errors. was wondering how come this is possible, and what purpose does it solve?

  • RELEVANCY SCORE 5.29

    DB:5.29: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 5.25

    DB:5.25:Non-Abstract Methods In A Abstract Class fj


    Abstract Class can contain Non-abstract methods.
    and Abstract Classes are not instantiable as well
    So,
    What is the purpose of Non-abstract methods in a Abstract class.
    since we can't create objects and use it

    so these non-abstract methods are only available to subclasses.
    (if the subclass is not marked as abstract)
    is that the advantage that has.(availability in subclass)

    ??

    DB:5.25:Non-Abstract Methods In A Abstract Class fj

    so these non-abstract methods are only available to
    subclasses.If they're public, they're available to any user of the class or of its concrete subclass. Same as the abstract metods. Same as interface methods. Same as public methods in a concrete class.

  • RELEVANCY SCORE 5.24

    DB:5.24: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:5.24: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 5.12

    DB:5.12:C#, Default Implementation Of Abstract Class Abstract Method 1d


     
    Hi!
     
    How do you provide default implementation of an abstract class' abstract method in the derived class? Please explain.
     
    Thank you.

    DB:5.12:C#, Default Implementation Of Abstract Class Abstract Method 1d

    You want to use 'virtual', not 'abstract' for the method declaration.  Abstract means virtual with no definition in that class.

  • RELEVANCY SCORE 5.05

    DB:5.05:Abstract Class And Interfaces jf


    Hi,

    In which senarios, we can choose abstract class and interfaces

    Thanks

    DB:5.05:Abstract Class And Interfaces jf

    Hi,

    The most important scenario of deciding when to use Abstract Class or an Interface comes by trying to establish an IS-A relationship (abstract class) or CAN-DO relationship (Interface) is found between the related objects.

    1. e.g.
    A "Manager" IS AN "Employee" and a "SoftwareEngineer" IS ALSO AN "Employee"
    so for this relationship we can create an "Employee" Abstract class and the other classes "Manager" and "SoftwareEngineer" should derive from it and may provide their own implementations...........

    2. e.g.
    There will an annual appraisal for all types of Employees in an Organization. so, all employees must establish a certain kind of contract to fulfill for Appraisal which is done by an "IAppraisal" interface which has 2 methods - viz. a). public void IncreaseGrade();
    b). public void IncreaseSalary(double percentage);

    Hope this clarifies the scenario.

    Other aspects to decide are Versioning and Ease of Use between the 2.

    For more: pl. refer Applied .Net Framework book by Jeffry Richter

  • RELEVANCY SCORE 5.01

    DB:5.01: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:5.01: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 5.01

    DB:5.01:Create Object For Abstract Class? ps


    Is any way to create object for an abstract class?

    DB:5.01:Create Object For Abstract Class? ps

    anonymous class means that a class is created and
    instantiated in a single line.. but how come abstract
    class allows this instantiation when there should be
    no way to create a object.. ?..

    is this a flaw or something ?..it's not the abstract class that's being instantiated, it's an anonymous concrete subclass that's being instantiated. don't be misled into confusing the reference type (AbstractClass) and the object itself, which is anonymous. consider the following

    Object a = new JFrame();we have a reference to an object, but the reference points to an instance of JFrame. same in my example, it's a reference to AbstractClass, but an instance of a subclass of AbstractClass. you need to understand the difference between references and objects

  • RELEVANCY SCORE 5.01

    DB:5.01:Constructor In An Abstract Class 8a


    Can a constructor be provided for an abstract class?

    DB:5.01:Constructor In An Abstract Class 8a

    Note: you can make a constructor for an abstract class public, but this is equivlenet to making it protected as the constructor can only be called by a derived class.

  • RELEVANCY SCORE 5.01

    DB:5.01:Abstract Class-Interface - Usage 71


    hai
    Give me details regarding the suituation of using
    1. Abstract class
    2. Interface

    DB:5.01:Abstract Class-Interface - Usage 71

    Basically an interface is a set of methods a class can promise to implement. An interface often expresses some aspect of a class that isn't related to the class hierarchy itself (that Dog, Duck and Cat extends Animal kind of stuff). It's often a common way to access stored objects like for example the Enumeration and Iterator interfaces.

    If a class has promised to implement an interface but doesn't, it becomes abstract. A class also becomes abstract if some methods are declared abstract. In both cases the class must be declared abstract and the actual implementation of the abstract methods is left over to subclasses.

    The reason for declaring a method abstract is one of design. The abstract class is often made to contain general information about something, and its subclasses are expected to fill in specific details by implementing the abstract methods. For example Animal can leave noise() abstract and let Dog, Duck and Cat provide the actual sounds.

  • RELEVANCY SCORE 5.01

    DB:5.01:Abstract Class s8


    for this example,
    public class xx {
    public abstract method1(){}
    ..
    }
    If the code is correct,a class not defined as an abstract class but contains abstract methods, does that make the class an abstract class. Can this class still have instantiate objects of its own? Thanks

    DB:5.01:Abstract Class s8

    Say you have a class that models something that is abstract, but you know what features it will have. You can use an abstract method to indicate this.

    For example, lets say I have an abstract class called Polygon. This is abstract, when you draw a polygon, you are actually drawing a specific type of polygon. However, you know you'd like to know some specific details about this polygon, say the number of sides. So we can define a polygon class:
    public abstract class Polygon
    {
    public abstract int numSides();

    // other methods, data, etc.
    }Polygon is an abstract idea; we don't know how many sides it has, so we can't provide the body of the method.

    So you have concrete subclasses that actually implement it:
    public class Triangle extends Polygon
    {
    public int numSides()
    {
    return(3);
    }
    }

    public class Rectangle extends Polygon
    {
    public int numSides()
    {
    return(4);
    }
    }Then when you use a Polygon reference:
    Polygon p;

    // more code ...
    // p is set to something that is a Polygon.
    // maybe more code still ...

    // p can refer to anything that is a Polygon.
    // For this example, p can really be a Triangle or a Rectangle
    // We don't know what it is, but we know we can find out how many sides it has.
    System.out.println("p has " + p.numSides() + " sides");

  • RELEVANCY SCORE 4.97

    DB:4.97:Constructor In Abstract Class 38


    What is the use of constructor in abstract class?

    DB:4.97:Constructor In Abstract Class 38

    An abstract class has fields etc. of it's own, which will require intialization. In fact the constructor in the super class may require arguments passed from the concrete class constructor.

    Constructors in abstract classes should generally be declared as protected and are always called from the concrete classes constructor, either through super() or implicitly.

  • RELEVANCY SCORE 4.89

    DB:4.89:Abstract Classes kc


    what is the main purpose of abstract classes. why abstract class do not throw exceptions.

    DB:4.89:Abstract Classes kc

    Hi,

    Why are classes implementing EntityBeans defined as Local declared as abstact classes.

    Seetesh

  • RELEVANCY SCORE 4.88

    DB:4.88:All The Methods Inside An Abstract Class Should Be Abstract Or Both Abstract And Non Abstaract? ck


    All the Methods inside an abstract class should be abstract or both abstract and non abstaract?

    T prabhakara Rao

    DB:4.88:All The Methods Inside An Abstract Class Should Be Abstract Or Both Abstract And Non Abstaract? ck

    Hi Prabhakara,
    Concrete class is nothing but normal class, we can use as a base class or may not.Not compulsory, it can't contain abstract methods.we can create object and work with this class.

    class Sample
    {
    public void MyMethod()
    {..............
    }
    }

    Abstract class:- Abstract class is class which declared with a keyword Abstract,
    Must be used as a base class.Only intension to declare a abstract class is to use as a base class,that is we can't create object of this class like concrete class.It can contain abstract methods as well as concrete(normal) methods.

    public abstract class MyClass
    {
    public void MyMethod()
    {..............}

    public abstract TestMethod()
    {
    . ........
    }
    }PS.Shakeer Hussain

  • RELEVANCY SCORE 4.88

    DB:4.88:Abstract Class &Amp; Interface jp


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

    DB:4.88: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 4.87

    DB:4.87:Abstract Method And Class x3


    I'm a beginner in Java and just learn about abstract method and class.
    However, i am wondering what is the point of using abstract method/class?
    Because when I delete the abstract method and change the class name to public class XXXX( changed from "abstract class XXXX), my program still runs well, nothing goes different.
    Is it because I haven't encountered any situation that abstract method is necessary or ?

    Thanks!

    DB:4.87:Abstract Method And Class x3

    excellent explanation jverd....I was struggling with this issue too- the way my book explains it was not clear....thanks!!!!

  • RELEVANCY SCORE 4.87

    DB:4.87:Abstract And Interface? cm


    why do we need abstract class?
    why do we need interface in java?

    DB:4.87:Abstract And Interface? cm

    Oh please, do some research of your own.

  • RELEVANCY SCORE 4.87

    DB:4.87:Abstract Class cp


    What is the definition of abstract class

    DB:4.87:Abstract Class cp

    Hi Gopi,
    The following is quoted from MSDN library.
    Abstract classes are closely related to interfaces.
    They are classes that cannot be instantiated, and are frequently either partially implemented, or not at all implemented.
    One key difference between abstract classes and interfaces is that a class may implement an unlimited number of interfaces, but may inherit from only one abstract (or any other kind of) class.
    A class that is derived from an abstract class may still implement interfaces.
    Abstract classes are useful when creating components because they allow you specify an invariant level of functionality in some methods, but leave the implementation of other methods until a specific implementation of that class is needed.
    They also version well, because if additional functionality is needed in derived classes, it can be added to the base class without breaking code

    Please see Abstact Classes for details.
    Best regards,
    Min Zhu [MSFT]
    MSDN Community Support | Feedback to us
    Get or Request Code Sample from Microsoft
    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

  • RELEVANCY SCORE 4.87

    DB:4.87:Concept Of Abstract Class &Amp; Interface fc


    Hi friends,

    My question is what is the main difference between Abstract class Interface?

  • RELEVANCY SCORE 4.87

    DB:4.87:Query On Abstract Class jj


    is it possible to extend an abstract class?

    DB:4.87:Query On Abstract Class jj

    All you need for a utility class all you need is a private constructor. e.g. the Math class
    You can have utility class which is abstract or final class as well.
    It just that abstract is usually meant for classes with abstract methods so it could be more confusing than useful.

  • RELEVANCY SCORE 4.87

    DB:4.87:Difference Between Inheritance And Abstract Class 9s


    difference between inheritance and abstract class

    DB:4.87:Difference Between Inheritance And Abstract Class 9s

    There was never an episode of Blackadder where he tried to con his aunt out of an abstract class

  • RELEVANCY SCORE 4.87

    DB:4.87:Interface Vs Abstract Class sa


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

    DB:4.87: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 4.87

    DB:4.87:Diffrence Between Abstract Class And Stack ca


    Can any one tell me the keydifferencebetween Abstract Class Stack ??

    Thanks.
    Rhythm

    DB:4.87:Diffrence Between Abstract Class And Stack ca

    They are entirely different concepts, so there isn'ta key difference I can think of. Maybe I'm missing something, care to elaborate?
    Thanks
    --mc

  • RELEVANCY SCORE 4.87

    DB:4.87:Test If Class Is Abstract By Reflection 3a


    Hi, may I find out if a some class is declared as abstract using class reflection??
    Radim

    DB:4.87:Test If Class Is Abstract By Reflection 3a

    thanks
    Class.GetModifiers() is the right method.

    Class.isInterface() is not for this test because
    relation between class and interface is defined in jvm as interface is naturally abstract (abstract class is not interface)...

  • RELEVANCY SCORE 4.87

    DB:4.87:Abstract Class 8k


    hiii,
    can u give an practical(program) example for abstract class

    DB:4.87:Abstract Class 8k

    CRKC wrote:
    hiii,
    can u give an practical(program) example for abstract classThe java.util.AbstractList class is a good example. It supplies almost a full ArrayList implementation. If you extend it you only need to impelement two methods and you got your very own MyArrayList.

  • RELEVANCY SCORE 4.87

    DB:4.87:Abstract Classes And Methods m3


    Is it legal or possible to implement a partial abstract class?

    For example:

    abstract class abclass{

    abstract void abmethod1(){}

    abstract void abmethod2(){}

    }

    final class ficlass extends abclass{

    //providing implementation for method abmethod1

    void abmethod1(){ //....

    return;
    }
    }
    // abmethod2 is not implemented in the class.

    Please provide some explantion if it can or cann't be done

    Thank you

    DB:4.87:Abstract Classes And Methods m3

    Thanks for the advice thomas.behr, but have no access to JDK right now, Hence decided to get some ideas from the forum.

  • RELEVANCY SCORE 4.87

    DB:4.87:Can An Abstract Class Extend Another Abstract Class? p1


    Is it possible for an abstract class to extend another abstract class?

    Say
    public abstract class AComponent extends JComponent {
    }

    Thanks.

  • RELEVANCY SCORE 4.87

    DB:4.87:Inner Classes ks


    Inner classes can contain abstract methods. So that inner class will become abstract class. Now my doubt
    is , will the outer class become abstract too?

    DB:4.87:Inner Classes ks

    You can define an abstract class inside another class, an interface, or inside a method (private to that method)
    Where you define it changes its scope, the file it is defined in and the name of the class fie. I don't think there is anything else to it.

  • RELEVANCY SCORE 4.87

    DB:4.87:Abstract Class And A Static Method a1


    Can i call a static method within an abstract class ?

    DB:4.87:Abstract Class And A Static Method a1

    Simply test this.
    abstract public class Abstract{
    public static void main(String[] args){
    System.out.println("main in an abstract class");
    }
    }

  • RELEVANCY SCORE 4.80

    DB:4.80:Need Help With Abstract Method ? 7p


    **************************************************
    public abstract void sleep()
    {
    ..........
    }
    **************************************************
    Could someone please tell me what is the difference of an abstract method in comparing to an instance or a class method? How should I do the invocation to an abstract method by other methods of its own class and of another class? Must I define abstract methods within abstract classes? Do I need to redefine abstract methods before using them? Thanx!

  • RELEVANCY SCORE 4.80

    DB:4.80:Re: Abstract Classes mp


    Delete constructor from your person abstract class, 'cause abstract class cann't be instantiated. Or better alternative to delete abstract keyword.

  • RELEVANCY SCORE 4.73

    DB:4.73:Why Are We Using Abstract Class? pp


    Why are we using Abstract class? What is specify use of Abstract class?

    DB:4.73:Why Are We Using Abstract Class? pp

    Thx for the lessons....that may help with an upcoming homework assignment.

  • RELEVANCY SCORE 4.72

    DB:4.72:Abstract Class sc


    What is the use of Abstract class with no abstract methods? Please let me a scnerio where this is used instead of a Normal class

    DB:4.72:Abstract Class sc

    There really isn't much point in such a class at all. But let me turn the question around: what would be the point of requiring an abstract class to have at least one abstract method?

  • RELEVANCY SCORE 4.72

    DB:4.72:Benefits Of Abstract Class Over A Extend Simple Calss 1a


    Hi friends,

    I would like to know the benifits of an Abstract class.
    Abstract class can't be instantiate. and we must provide implemention when you extend an abstract class or else we have make that class as abstract.

    other than this is ther any other benefits.

    Thanks
    Dora Babu,

    DB:4.72:Benefits Of Abstract Class Over A Extend Simple Calss 1a

    An abstract class is useful if you have some core implemented methods/helper methods for the sub classes to use. For example you might want some very basic immutable rules for all your classes that you could implement in an abstract base class.

    If, however, all methods are abstract then I strongly recommend that you use an interface instead as you can implement without having to use up your single inheritance. In fact, I often implement OO models that have all behaviour defined in interfaces but with a few abstract classes as well that just provide default behaviour. In this way, you can get the benefits of reuse from extending the abstract classes but if you really need to extend another class (e.g. to fit in with an external API) you are still do so and you can implement all the required interface methods from scratch.

    Dom.

  • RELEVANCY SCORE 4.70

    DB:4.70:Abstract Class m3


    hi
    Can we have a constructor for an abstract class, and can we
    create an object for an abstract class?

    regards.

    DB:4.70:Abstract Class m3

    tjacobs01 wrote:
    JComponent jc = new JComponent(); //won't work
    JComponent jc2 = new JComponent() {}; //this works

    See the difference?(You may need glasses to see the difference ;-)

  • RELEVANCY SCORE 4.70

    DB:4.70:Differance Between Abstract Class And Interface 7s


    Whats the main differance between abstract class and Interface and where I can use abstract class and where I can use Interface

    DB:4.70:Differance Between Abstract Class And Interface 7s

    Refer to
    http://www.javaworld.com/javaworld/jw-09-2001/jw-0921-interface.html

  • RELEVANCY SCORE 4.70

    DB:4.70:Abstract Class ad


    can we inherit more classes from an abstract class?

    DB:4.70:Abstract Class ad

    Hi
    Kommanaboyina,
    Welcome to MSDN Forums!

    If your question has been solved, please dont forget mark/vote the replies which helped you, and this will encourage the other community members to join in
    discussion and help each one.

    Have a nice day!
    Mike
    *****************************************************
    [All-In-One Code Framework]
    Sample world! You will get more from this world!
    Welcome to the new world!

  • RELEVANCY SCORE 4.69

    DB:4.69: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:4.69: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 4.66

    DB:4.66:Abstract Class Doubt ?? 7k


    what's the difference between the first abstract class and second abstract class .. when and where to use the first type and second type .. Please give me some info on it ...

    First Abstract Class
    public abstract class TestT where T : class
    {

    }

    Second Abstract Class

    public abstract class Test
    {

    }Regards, Gullu.

    DB:4.66:Abstract Class Doubt ?? 7k

    The second class is just a general abstract class - class that cannot be instantiated and is meant to provide common definition of a base class that multiple derived classes can share.
    More about abstract classes on MSDN.
    The first one is a generic abstract class that uses constraints to place requirements on the generic parameter (T). In your case the generic parameter can only be a type that match or inherit from specific base (you call this type 'class').
    e.g.

    public class Testable
    {

    public void Test()
    {
    //some logic here
    }

    }

    public abstract class TestT where T : Testable
    {
    public T t1;

    public void DoWork()
    {
    t1.Test(); //this will work because T must be of type Testable
    }
    }

    More about constraints on MSDN.

  • RELEVANCY SCORE 4.66

    DB:4.66:About Abstract Class df


    Hi All,

    I m inherting from abstract class . So is it mandatory for me to provide implemenation for all methods that r defined in abstract class

    i m getting error like this:

    subclass class is not abstract ,does not override abstract method "methodname" in superclass

    Thanks in advance

    Waiting for replies

    Amar

    DB:4.66:About Abstract Class df

    - you need to override all methods from your abstract
    superclass.....You don't have to override anything unless you want to, but you have to supply implementation for all abstract classes. If you don't you will have to declare the subclass abstract and let another subclass down the hierarchy finish the job. Eventually all abstract classes must be implemented otherwise objects cannot be instantiated. For that a class must be fully concrete.

  • RELEVANCY SCORE 4.66

    DB:4.66:Abstract Class Extends Other Class? cs


    What happens when a abstract class extends other class?
    How can we use the abstract class late in other class?
    Why do we need an abstract class that extends other class?
    for example:-
    public abstract class ABC extends EFG {
    }

    public class EFG{
    private String name="";
    private int rollno="";
    private void setName(int name)
    {
    this.name=name;
    }
    private String getName()
    {
    return this.name;
    }
    }

    DB:4.66:Abstract Class Extends Other Class? cs

    shafiur wrote:
    Why do we need an abstract class that extends other class?Addiction to inheritance?

  • RELEVANCY SCORE 4.66

    DB:4.66:Abstract Class,No Constructor Usage Problems????-- pd


    can an abstract class without any constructor be used?

    please guide

    DB:4.66:Abstract Class,No Constructor Usage Problems????-- pd

    Come on... Please do some research before you start asking questions... A simple search will give you more then enough information!

    Here for example: http://java.sun.com/docs/books/tutorial/java/javaOO/abstract.html

  • RELEVANCY SCORE 4.66

    DB:4.66:Abstract Class fd


    why we can not create object of an abstract class.

    DB:4.66:Abstract Class fd

    How many dodos were born last year?too many to count

  • RELEVANCY SCORE 4.59

    DB:4.59:When To Use Abstract Class And Interface 3z


    What is the scenario to use abstract class and interface

    DB:4.59: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 4.59

    DB:4.59: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:4.59: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 4.59

    DB:4.59: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:4.59: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 4.58

    DB:4.58:Abstract Class 8s


    What does it mean to declare a class as abstract?

    DB:4.58:Abstract Class 8s

    If you have at least one abstract method in your
    class, that class must be abstract.

    If you implement any interface and you dont override
    all methods of that interface, your class must be
    declared abstract.

    If you extend an abstract class and you dont override
    all abstract methods of the parent class, your class
    must be declared abstract.

    Abstract generally is used to create an specific
    behavior available to all subclasses. And each
    subclass must override that abstract method in such a
    specific behavior.

    I think thats it.There's one more situation. It's when you declare a fully concrete class to be abstract. It's useful when you want a class to act as superclass but you want to supply a default implementation to all methods. Subclasses only have to override what they want to change.

  • RELEVANCY SCORE 4.58

    DB:4.58:Abstract Class cp


    under what kinda of program development.. we will code abstract class and use them in java?

    DB:4.58:Abstract Class cp

    or...
    java.philosophy.AbstractThought
    java.art.AbstractPainting
    java.statistics.Abstract

  • RELEVANCY SCORE 4.58

    DB:4.58:Constructor In An Abstract Class xj



    Can we have a constructor in an Abstract class??

    DB:4.58:Constructor In An Abstract Class xj


    You can't instantiate an abstract class but you can have a constructor. It is only ever called, however, when instantiating an object of a subclass. ( Indeed, it MUST be called in the most recent releases ).

  • RELEVANCY SCORE 4.57

    DB:4.57: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:4.57: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 4.57

    DB:4.57:Abstract Class And Interface z1


    What is most important thing about abstract class and interface.

    When to use abstract class and interface.

    DB:4.57: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 4.54

    DB:4.54: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:4.54: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 4.54

    DB:4.54:Problems With Abstract Class ca


    I have abstract class i also have another class that extends from the abstract class.
    Question, can i create and array of the type abstract class and if i can isn't that contradicting the rules of Java where it say you can not instantiate an instant of an abstract class.

    here is the abstract class
    pawnItemClass[] array = new pawnItemClass[100];

    DB:4.54:Problems With Abstract Class ca

    I have abstract class i also have another class that
    extends from the abstract class.
    Question, can i create and array of the type abstract
    class and if i can isn't that contradicting the rules
    of Java where it say you can not instantiate an
    instant of an abstract class.

    here is the abstract class
    pawnItemClass[] array = new pawnItemClass[100];You are correct. You cannot instantiate the abstract class. However, your pawnItemClass array will NOT actually contain pawnItemClass objects. It will contain the derived class objects that have been casted up to pawnItemClasses.

    So, for example:

    public abstract class A {
    }

    public class B extends A {
    }

    You COULD do this:

    A[] array = new A[5]; (you haven't instantiated anythign other than an array - it's what the array is holding that you are worried about)

    But you could NOT do this:

    array[0] = new A();

    You COULD do this:

    array[0] = new B();

  • RELEVANCY SCORE 4.54

    DB:4.54:Regarding Java.Lang.Object Class pj


    Is java.lang.Object class an abstract class ?

    DB:4.54:Regarding Java.Lang.Object Class pj

    easy way to find out is to look in API. quicker than ask here.
    http://java.sun.com/j2se/1.3/docs/api/

  • RELEVANCY SCORE 4.52

    DB:4.52:About Abstract Class cd


    What are the advantages of using Abstract class and method while using Inheritance or Polymorphism?

    DB:4.52:About Abstract Class cd

    What are the advantages of using Abstract class and
    method while using Inheritance or Polymorphism?Advatantageous in relation to what. A concrete method? The advantage is that the compiler will enforce that the abstract class of the superclass is implemented in the subclass. If it's a concrete class the subclasses may override it but doesn't have to.

    So using abstract methods ENFORCES that they get overridden.

  • RELEVANCY SCORE 4.51

    DB:4.51:Abstract Methods... j9


    Hi i was going over abstract Classes and methods , I understood the abstract classes pretty well (they are basically used as parent super classes) but i still am not sure about abstract methods.. I know that if a class has an abstract method then that class must also be declared as an abstract class ... I know that abstract methods dont have a body ? Could anyone please give me why abstract methods are used and explain them thanks ....

    DB:4.51:Abstract Methods... j9

    SilverChips wrote:
    Thanks for the help man ... that what i needed to know. Glad you're moving forward. :)

  • RELEVANCY SCORE 4.51

    DB:4.51:Re: Interface m8


    Java Glossary : interface vs abstract class
    Abstract classes vs. interfaces: When does it make sense to choose an abstract class over an interface?
    Abstract classes and interfaces practicum: Move from theory to practice on when to employ abstract classes vs. interfaces
    Tech Tips: ABSTRACT CLASSES VS. INTERFACES

    DB:4.51:Re: Interface m8

    I'm still entertained by the fact that some folks will
    spell out words like "multiple", "inheritance",
    "interface", and "implement", but not "because".

    :o)LOL!

    This kills me - just bcuz.

    %

  • RELEVANCY SCORE 4.51

    DB:4.51:Public Abstract Interface Filterconfig pf


    public abstract interface FilterConfig

    what is this class actually . is it abstract class or interface?

    DB:4.51:Public Abstract Interface Filterconfig pf

    interfaces are abstract because you cannot
    instantiate them.

    like you cant instantiate a abstract class.It's the other way around. You cannot instantiate them because they're abstract. Only what's fully concrete can be instantiated.

  • RELEVANCY SCORE 4.51

    DB:4.51:Regarding Java.Lang.Object Class kj


    Is java.lang.Object class a abstract class ?

    DB:4.51:Regarding Java.Lang.Object Class kj

    In fact you can instanciate it, though about the only use I know for it is as a semaphore for synchronize.

  • RELEVANCY SCORE 4.51

    DB:4.51: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:4.51: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 4.50

    DB:4.50:Can We Write Constructor For Abstract Class? 83


    Can we write Constructor for Abstract class?

    DB:4.50:Can We Write Constructor For Abstract Class? 83

    Somebody's knee-deep in Grolsch.Who? Who is? Whowhowho? Tellmetellmetellme!

    kind regards,

    Jos (the liquor store guy still didn't refill my stock ... thirsty ;-)

  • RELEVANCY SCORE 4.50

    DB:4.50:Httpservlet Class In Abstract Class 8z


    HttpServlet class is an abstract class. but we dont override all the methods why?

    DB:4.50:Httpservlet Class In Abstract Class 8z

    Perhaps it was designed so that vendors can inherit and add additional functionality but of course, Sun implemented the fundamental logic to support the HTTP standards

  • RELEVANCY SCORE 4.50

    DB:4.50:Abstract Classes And Jaxb Context In Jbossws mm



    Hi All,Suppose there is an abstract class A with a derived concrete class B:

    public abstract class A {
    ...
    }

    public class B extends A{
    }

    DB:4.50:Abstract Classes And Jaxb Context In Jbossws mm


    I found a solution to add @XmlSeeAlso in abstract classes.Is there any other solution?Bests,Soheil

  • RELEVANCY SCORE 4.50

    DB:4.50:Abstract Class And Interface 18


    what is the difference between abstract class and interface

  • RELEVANCY SCORE 4.50

    DB:4.50:Re: Public Abstract Static... In Abstract Class? 39


    And have you ever heard about instanceof or getClass()?

    DB:4.50:Re: Public Abstract Static... In Abstract Class? 39

    I second rene's opinion that the design stinks. If you need to do something like this, then generally it means you are trying to do something outside the Ping or Pong class that should be done inside the class. For example:
    if (packet.getPacketType() == Packet.PING)
    doSomething();
    else if (packet.getPacketType() == Packet.PONG)
    doSomethingElse(); Should probably be handled like:
    public abstract class Pacaket {
    public abstract void doThing();
    }
    public class Ping extends Packet {
    public void doThing() { doSomething(); }
    public void soSomeThing() { ... }
    }
    public class Pong extends Packet {
    public void doThing() { doSomethingElse(); }
    public void doSomethingElse() { ... }
    }

    //...
    packet.doThing();

  • RELEVANCY SCORE 4.50

    DB:4.50:Abstract Class Or Interface ? 11


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

    DB:4.50: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 4.50

    DB:4.50:Abstract Class zx


    Hi,
    When to prefer abstract class without any method as abstract?

    Regards
    SamyMohan

    DB:4.50:Abstract Class zx

    wait grr.. I think I got it backward :-p.
    You need to implement abstract methods, and you do not need to implement non-abstract methods (but you can).
    ~sorry, I just woke up

  • RELEVANCY SCORE 4.50

    DB:4.50:Interface Vs Abstract Class d8


    when do we need interface and when abstract class?

    DB:4.50:Interface Vs Abstract Class d8

    2.All the abstract methods must be overrided and
    implemented by the child class.by definition, you can't override a method that has no implementation

    3.Real Examples:

    when we implement the ActionListener interface for
    Button click event then we have to override the
    actionPerformed method, we dont have any other
    chices, so it is a way of forcing the inherited class
    to override certain methods.as before, we implement an abstract method. you're not forcing an override, this can't be done, nor would it be a good idea. as discussed at length recently :-)

    n java you can see all the classes that starts with
    Abstract is abstract.not so. there's nothing at all to stop you writing a concrete class named AbstractClass

  • RELEVANCY SCORE 4.50

    DB:4.50: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:4.50: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 4.48

    DB:4.48:Abstract Class z3


    hi
    why we are declaraing a class as abstract.. Instead of declaring abstract , we can write the method inside the class and override it when neccessary by extending it.
    thanks

    DB:4.48:Abstract Class z3

    I think what you are trying to express is "why have abstract methods, methods without
    implementations, when you can always provide a 'dummy' implementation and then
    override that in concrete subclasses."

    I believe the main problem with that is that it's easy to forget to override this method,
    and this mistake can be discovered at compile-time, thanks to abstract methods.

  • RELEVANCY SCORE 4.48

    DB:4.48:Abstract Class 3s


    C# Abstract- Why we use Abstract Class?
    Details:

    Pros ????????Cons ???????

    DB:4.48:Abstract Class 3s

    In thier Core both Abstract Classes and Interfaces have similiarties:
    They cannot be instantiated, but can be used as variables (so anything that inherits/implements them can be feed to a function). Both allow defining wich functions all inheritors/implementers have to code out. Both allow to define Varriables the resulting
    class will have (Interfaces via properties, AC via variables or Properties).

    The only difference is that abstract classes are classes. A class can only inherit a single class, but inherit infinite amounts of interfacces. Designers choose AC when the classes functionality are the main purpose of whatever will code it out.

    IComparable allows comparing. No mater where you implement it, Comparability is only a small, unimportant part of the class. A minor feature.
    DBConnection is an abstract class. No mater what you derive from it, being a Db Conenction is it's main purpose. It cannot also be a window, a button, or some other class. Wich is very important, as DBConnections have to be used and recycled as fast as possible
    (in case you forgot to dispose of it).

    Generally, you do not need to write abstract classes. 95% of all times you ask yourself, Interfaces are the right answer. Unless you write some class library or need to write a common baseclass for your own little class heirarchy, you will not need abstract
    classes.Let's talk about MVVM: http://social.msdn.microsoft.com/Forums/en-US/wpf/thread/b1a8bf14-4acd-4d77-9df8-bdb95b02dbe2

  • RELEVANCY SCORE 4.48

    DB:4.48:Doubt About Incomplete Keyword In Abstract Class a7


    Hai,
    I have a doubt about the usage of "incomplete" keyword in abstract class.will any body explain me the same ?
    Also is there any way not to override an abstract method defined in an abstract class, in a class extending the abstract class ?
    Thanks in advance

    DB:4.48:Doubt About Incomplete Keyword In Abstract Class a7

    I have a doubt about the usage of "incomplete"
    mplete" keyword in abstract class.will any body
    explain me the same ?There is no such keyword.

    Also is there any way not to override an
    erride an abstract method defined in an abstract
    class, in a class extending the abstract class ?Yes, by declaring the subclass as abstract.

  • RELEVANCY SCORE 4.47

    DB:4.47:What Is Abstract Class ? 3p


    What is Abstract Class ?
    What is Method Decleration
    What is Implementation

  • RELEVANCY SCORE 4.46

    DB:4.46: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:4.46: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 4.44

    DB:4.44:Geting Subclass Info From Abstract Class jc


    Does ne one know how i can retreive informtion from the subclasses of an abstract class by creatinig an instance of the abstract class.

    are Methods such as getClass used?

    DB:4.44:Geting Subclass Info From Abstract Class jc

    Cast your HorDent and HinDent objects to Dent and call
    the above method. No need to explicitly cast to a super-type.

  • RELEVANCY SCORE 4.44

    DB:4.44:Make Abstract Class With Interface. 39


    I want to make an abstract class with methods that need interfacing, but I don't want to make an entire other class for the abstract class to implement. Is there any way to make an abstract class and interface combined into one class with no implementations on that class?

    DB:4.44:Make Abstract Class With Interface. 39

    if you want a class with no implementations that what you need is an Interface

  • RELEVANCY SCORE 4.44

    DB:4.44:Abstract Class........ jd


    Dear All,
    " class that defines an abstract method can call that method as well". Please explain its real meaning.

    DB:4.44:Abstract Class........ jd

    And if you're wondering what could be the use of this, search for the "Template Method" design pattern.

    Basically, a concrete method of the superclass calls a series of abstract methods (different steps) that the subclasses are to implement.

    This way, the superclass controls the flow of execution (by defining the program skeleton) while leaving to the subclasses the freedom (or burden) to implement the list of abstract methods.

  • RELEVANCY SCORE 4.44

    DB:4.44:Interfaces And Abstract Classes 8x


    Whats the difference between an interface and an abstract class.

    DB:4.44:Interfaces And Abstract Classes 8x

    Another trait that is often overlooked is that the abstract methods and constants declared in an interface are always public; with abstract classes, you can declare them (package) and protected scope as well.

  • RELEVANCY SCORE 4.44

    DB:4.44:Abstract Class Httpurlconnection 3z


    How do we instantiate the HttpURLConnection abstract class.

    Any help would be great

    Thanks

    DB:4.44:Abstract Class Httpurlconnection 3z

    hi,
    You would first require to create a URL object and then from that you would create an object of the HttpURLConnection.. for eg..

    try
    {
    URL url = new URL("http://.....");
    HttpURLConnection httpConnection = (HttpURLConnection) url.openConnection();

    httpConnection.setDoInput(true); //default is true
    //default for output is false, so if you want to send info you would have to explicitly set this flag..
    httpConnection.setDoOutput(true);
    httpConnection.setUseCaches(false);
    //// other code to come here ////
    }
    catch(Exception ex)
    {
    System.out.println("Exception :" + ex);
    }hope that helpz

    cheerz
    ynkrish

  • RELEVANCY SCORE 4.44

    DB:4.44:Re: Abstract Class-Interface kk


    why abstract class is faster than interface?

    Because mauve has the most RAM.

    ~

    DB:4.44: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 4.44

    DB:4.44:Can We Declare A Private Method Inside The Abstract Class? xs


    Can we declare a private method inside the abstract class?

    DB:4.44:Can We Declare A Private Method Inside The Abstract Class? xs

    Too much work. He's probably asking what his boss's email id is on some forum somewhere.

  • RELEVANCY SCORE 4.44

    DB:4.44:Ejb2.0 Inheritance In Jboss kd


    hi,

    We are trying to migrate an ejb 2.0 project from Websphere Application Server 6.1 to Jboss 4.2.3.
    Our project has used Entity Bean inheritance using Websphere application server. While we are deploying it
    in jboss the inheritance entites showing sql exceptions as follows.

    Is the entity bean inheritance in ejb 2.0 is supported by jboss application server 4.2?.Please respond as soon as possible.

    Thanks in advance

    Warm Regards

    Jisson Dennis
    ------------------------------------------------------------------------------------------

    Stacktrace

    TransactionRolledbackLocalException in method: public abstract boolean com.eyi.core.persistence.ejb2.PersistentEntity.isDeleted(), causedBy:
    com.microsoft.sqlserver.jdbc.SQLServerException: Invalid column name 'name'.
    at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDatabaseError(SQLServerException.java:156)
    at com.microsoft.sqlserver.jdbc.SQLServerStatement.getNextResult(SQLServerStatement.java:1373)
    at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.doExecutePreparedStatement(SQLServerPreparedStatement.java:371)

    -------------------------------------------------------------------------------------------------

    Base entity
    -----------

    public abstract class StaffOnProbationBean extends com.eyi.hrms.staff.ejb.StaffLifeCycleStateBean {

    public abstract void setHomeJNDIName(String homeJNDIName);

    public abstract String getHomeJNDIName();

    public abstract java.sql.Date getPlannedEndDate();

    public abstract void setPlannedEndDate(java.sql.Date newPlannedEndDate);

    public abstract short getNoOfTimesExtended();

    public abstract void setNoOfTimesExtended(short newNoOfTimesExtended);

    public abstract boolean getLatest();

    public abstract void setLatest(boolean newLatest);
    }

    ----------------------------------------------------------------------------------------------
    Child Entity
    -----------

    public abstract class StaffLifeCycleStateBean extends com.eyi.oms.persistence.OrganizationalEntityBean implements javax.ejb.EntityBean {

    public void ejbStore()
    {
    preStore();
    }

    public abstract java.lang.String getUUID();

    public abstract void setUUID(java.lang.String newUUID);

    public abstract java.lang.String getName();

    public abstract void setName(java.lang.String newName);

    public abstract boolean getActive();

    public abstract void setActive(boolean newActive);

    public abstract java.lang.String getOfficeID();

    public abstract void setOfficeID(java.lang.String newOfficeID);

    public abstract java.sql.Date getCreatedDate();

    public abstract void setCreatedDate(java.sql.Date newCreatedDate);

    public abstract java.sql.Date getLastModifiedDate();

    public abstract void setLastModifiedDate(java.sql.Date newLastModifiedDate);

    public abstract long getOCA();

    public abstract void setOCA(long newOCA);

    public abstract boolean getDeleted();

    public abstract void setDeleted(boolean newDeleted);

    public abstract java.sql.Date getStartDate();

    public abstract void setStartDate(java.sql.Date newStartDate);

    public abstract java.sql.Date getEndDate();

    public abstract void setEndDate(java.sql.Date newEndDate);

    public abstract java.lang.String getHomeJNDIName();

    public abstract void setHomeJNDIName(java.lang.String newHomeJNDIName);

    public abstract java.util.Collection getRelations();

    public abstract void setRelations(java.util.Collection aRelations);

    public abstract com.eyi.hrms.staff.ejb.Staff getStaff();

    public abstract void setStaff(com.eyi.hrms.staff.ejb.Staff aStaff);

    public com.eyi.core.persistence.PersistentEntityKey ejbCreate()
    throws javax.ejb.CreateException
    {
    return null;
    }

    public void ejbPostCreate() throws javax.ejb.CreateException
    {
    }

    //public abstract java.lang.String getStaff_uUID();

    //public abstract void setStaff_uUID(java.lang.String newStaff_uUID);
    }

    DB:4.44:Ejb2.0 Inheritance In Jboss kd

    hi,

    We are trying to migrate an ejb 2.0 project from Websphere Application Server 6.1 to Jboss 4.2.3.
    Our project has used Entity Bean inheritance using Websphere application server. While we are deploying it
    in jboss the inheritance entites showing sql exceptions as follows.

    Is the entity bean inheritance in ejb 2.0 is supported by jboss application server 4.2?.Please respond as soon as possible.

    Thanks in advance

    Warm Regards

    Jisson Dennis
    ------------------------------------------------------------------------------------------

    Stacktrace

    TransactionRolledbackLocalException in method: public abstract boolean com.eyi.core.persistence.ejb2.PersistentEntity.isDeleted(), causedBy:
    com.microsoft.sqlserver.jdbc.SQLServerException: Invalid column name 'name'.
    at com.microsoft.sqlserver.jdbc.SQLServerException.makeFromDatabaseError(SQLServerException.java:156)
    at com.microsoft.sqlserver.jdbc.SQLServerStatement.getNextResult(SQLServerStatement.java:1373)
    at com.microsoft.sqlserver.jdbc.SQLServerPreparedStatement.doExecutePreparedStatement(SQLServerPreparedStatement.java:371)

    -------------------------------------------------------------------------------------------------

    Base entity
    -----------

    public abstract class StaffOnProbationBean extends com.eyi.hrms.staff.ejb.StaffLifeCycleStateBean {

    public abstract void setHomeJNDIName(String homeJNDIName);

    public abstract String getHomeJNDIName();

    public abstract java.sql.Date getPlannedEndDate();

    public abstract void setPlannedEndDate(java.sql.Date newPlannedEndDate);

    public abstract short getNoOfTimesExtended();

    public abstract void setNoOfTimesExtended(short newNoOfTimesExtended);

    public abstract boolean getLatest();

    public abstract void setLatest(boolean newLatest);
    }

    ----------------------------------------------------------------------------------------------
    Child Entity
    -----------

    public abstract class StaffLifeCycleStateBean extends com.eyi.oms.persistence.OrganizationalEntityBean implements javax.ejb.EntityBean {

    public void ejbStore()
    {
    preStore();
    }

    public abstract java.lang.String getUUID();

    public abstract void setUUID(java.lang.String newUUID);

    public abstract java.lang.String getName();

    public abstract void setName(java.lang.String newName);

    public abstract boolean getActive();

    public abstract void setActive(boolean newActive);

    public abstract java.lang.String getOfficeID();

    public abstract void setOfficeID(java.lang.String newOfficeID);

    public abstract java.sql.Date getCreatedDate();

    public abstract void setCreatedDate(java.sql.Date newCreatedDate);

    public abstract java.sql.Date getLastModifiedDate();

    public abstract void setLastModifiedDate(java.sql.Date newLastModifiedDate);

    public abstract long getOCA();

    public abstract void setOCA(long newOCA);

    public abstract boolean getDeleted();

    public abstract void setDeleted(boolean newDeleted);

    public abstract java.sql.Date getStartDate();

    public abstract void setStartDate(java.sql.Date newStartDate);

    public abstract java.sql.Date getEndDate();

    public abstract void setEndDate(java.sql.Date newEndDate);

    public abstract java.lang.String getHomeJNDIName();

    public abstract void setHomeJNDIName(java.lang.String newHomeJNDIName);

    public abstract java.util.Collection getRelations();

    public abstract void setRelations(java.util.Collection aRelations);

    public abstract com.eyi.hrms.staff.ejb.Staff getStaff();

    public abstract void setStaff(com.eyi.hrms.staff.ejb.Staff aStaff);

    public com.eyi.core.persistence.PersistentEntityKey ejbCreate()
    throws javax.ejb.CreateException
    {
    return null;
    }

    public void ejbPostCreate() throws javax.ejb.CreateException
    {
    }

    //public abstract java.lang.String getStaff_uUID();

    //public abstract void setStaff_uUID(java.lang.String newStaff_uUID);
    }

  • RELEVANCY SCORE 4.44

    DB:4.44:Can Abstract Classes Inherit Abstract Methods Without Implementing Them? dj



    Keeping with your example: Just remove the declaration of DoSomething() from the Bar class. Since the class is declared as abstract, it doesn't need to implement any abstract methods from its base class.


    public abstract class Foo : MonoBehaviour { public abstract void DoSomething (); }


    public abstract class Bar : Foo { // No declaration of DoSomething(); // Just add new methods. }

    DB:4.44:Can Abstract Classes Inherit Abstract Methods Without Implementing Them? dj


    Keeping with your example: Just remove the declaration of DoSomething() from the Bar class. Since the class is declared as abstract, it doesn't need to implement any abstract methods from its base class.


    public abstract class Foo : MonoBehaviour { public abstract void DoSomething (); }


    public abstract class Bar : Foo { // No declaration of DoSomething(); // Just add new methods. }

  • RELEVANCY SCORE 4.44

    DB:4.44:In Which Case We Need : An Abstract Class With No Abstract Methods.... 9p


    Does it make sense to have an abstract class with no abstract methods. (means any design pattern or scenario)

    DB:4.44:In Which Case We Need : An Abstract Class With No Abstract Methods.... 9p

    Most of (or maybe all) the adapter classes corresponding to AWT listeners are abstract with no abstract methods. These classes are abstract as it just doesn't make sense to use a listener that does nothing.

  • RELEVANCY SCORE 4.44

    DB:4.44:When To Use Abstract Class And Interface? jp


    hi,

    When to use Abstract class and Interface?

    DB:4.44:When To Use Abstract Class And Interface? jp

    Thanks for all, i got some clear idea about when to use interface and abstract class.

  • RELEVANCY SCORE 4.44

    DB:4.44:Interface And Abstract Class c3


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

    DB:4.44:Interface And Abstract Class c3

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

    Double your pleasure or not!

  • RELEVANCY SCORE 4.44

    DB:4.44:Abstract Class kz


    I have an abstract class that looks something like this:

    DB:4.44:Abstract Class kz

    You would need to create an instance object, since neither the class nor the class member is static. However, your posted class is declared as abstract. You cannot create instances of abstract classes, which designed to be inherited by other class. Abstract classes can be used to provide a minimum default behavior for inheriting classes. I like to use them as Object Factories for inheriting classes. You must define another class that inherits Checking, and then instantiate that class. class CheckingDerived : Checking { } Then somewhere else in your code would create an instance of the class and access Location. CheckingDerived cd = new CheckingDerived(); string homeLocation = cd.Location; Hope this helps. Rudy  =8^DMark the best replies as answers. Fooling computers since 1971.

  • RELEVANCY SCORE 4.44

    DB:4.44: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:4.44:Abstract Class And Interface???? ja

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

  • RELEVANCY SCORE 4.44

    DB:4.44:Extend Abstract Class By Another Abstract Class p3


    Hi,
    I am trying to extend an abstract class(with one abstract function) in another abstract class but its giving a nativeclassdefination error.
    Kindly guide me if it is possible to do so or not.

    DB:4.44:Extend Abstract Class By Another Abstract Class p3

    In general this should work fine. I assume you are trying to extend a system specific class if you get such an exception, perhaps you can elaborate on what you are doing.

  • RELEVANCY SCORE 4.44

    DB:4.44:Object Of An Abstract Class f3



    Can we create object of an abstract class ?

    DB:4.44:Object Of An Abstract Class f3


    As Richard Brnning mentioned in his reply, we can't instantiate the object with reference to the Abstract Class. i.e.

    DATA: O_OBJ TYPE REF TO ZCL_ABS_CLASS.
    CREATE O_OBJ. " This will give syntax error

  • RELEVANCY SCORE 4.44

    DB:4.44:Java Interfaces And Abstract Classed fc


    what is the difference between interface and abstract class?

    DB:4.44:Java Interfaces And Abstract Classed fc

    I suggest you try writing some code and see.

  • RELEVANCY SCORE 4.44

    DB:4.44:Abstract Class Implementation Dos Prompt c9


    Hello everyone,
    Good day! Anyone knows how to implement or use abstract class to another class. Pls.... help me. I'm still a novice programmer. Program like Bank Account with a abstract class named 'Account' and an another class 'Savings' extends the abstract class and also the third class named 'TimeDeposit' something like it.

    DB:4.44:Abstract Class Implementation Dos Prompt c9

    Hello everyone,
    Good day! Anyone knows how to implement or
    use abstract class to another class. Pls.... help
    me. I'm still a novice programmer. Program like Bank
    Account with a abstract class named 'Account' and an
    another class 'Savings' extends the abstract class
    and also the third class named 'TimeDeposit'
    something like it.One thing to remember is that your class has to include code for all methods that are marked abstract in the abstract class you are extending; and if you don't want anyone else extending your class, you should make it final. You should also check the abstract class's constructors to see if you need to call a particular one when you are constructing your class. If you do, you'll need to call super(...) in your class's constructor, and it should be the first statement.

  • RELEVANCY SCORE 4.44

    DB:4.44:How Abstract Class Works? 13


    hello, every!

    i can't quite understand the abstract class.

    can a abstract class be inherited by a class in different package?

    thanks!

  • RELEVANCY SCORE 4.44

    DB:4.44:Servlet x7


    if HttpServlet is abstract class then HttpServlet have an abstract methods?

    DB:4.44:Servlet x7

    if HttpServlet is abstract class then HttpServlet have an abstract methods?

  • RELEVANCY SCORE 4.44

    DB:4.44:Use Of Abstract And Interface? k3


    when i use Abstract class or Interface.Which one is better?

    DB:4.44:Use Of Abstract And Interface? k3

    Depends on what you want to do. An interface is more general (in that it doesn't define any actual behavior) and allows you to mimic multiple inheritance (a class can implement any number of interfaces whereas it can only extend one class (abstract or otherwise)). Abstract is good if you have a common base of functionality that all of the implementers will be using.

    It's also fairly common to use both (i.e. the interface TableModel and the abstract class AbstractTableModel), so that someone who wants to completely write their own implementation is free to, while someone who wants to just extend or change the standard functionality could do that as well.

  • RELEVANCY SCORE 4.44

    DB:4.44:What Is Abstract Class? zs


    Hi,
    What is abstract class?

    How can we create an abstract class?

    Pooja.

    DB:4.44:What Is Abstract Class? zs

    public abstract class ABSDemo{

    public void main(String s)
    {
    System.out.println(s);
    }
    }

    is an abstract class ?

    Pooja

  • RELEVANCY SCORE 4.44

    DB:4.44:A Problem About The Abstract Class And The Abstract Method, Coming For Help mc


    Why the abstract method getScreenSize() in the abstract class java.awt.Toolkit class can be called and return the right result?

    DB:4.44:A Problem About The Abstract Class And The Abstract Method, Coming For Help mc

    to paulcw:
    Yes, that's the very answer i'm looking for. Thanks for your reply, that really helps.