• RELEVANCY SCORE 4.37

    DB:4.37:Abstract Class 13




    Difference between abstract class and interface
    use of abstract class

    DB:4.37: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 4.11

    DB:4.11:Difference Between Inheritance And Abstract Class 9s




    difference between inheritance and abstract class

    DB:4.11: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 4.01

    DB:4.01: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:4.01:Differance Between Abstract Class And Interface 7s

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

  • RELEVANCY SCORE 3.89

    DB:3.89: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:3.89: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 3.89

    DB:3.89:Abstraction 3p


    if a class extends an abstract class does the subclass have to implement all abstract methods in the abstract class?
    e.g
    abstract class Shape
    {
    public abstract double area();
    public abstract double perimeter();
    }
    class Rec Extends Shape
    {
    }
    --- Does class Rec have to implement both area() and perimeter() methods or can it choose to implement area only? Please help

  • RELEVANCY SCORE 3.74

    DB:3.74: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:3.74: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 3.72

    DB:3.72: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:3.72: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 3.69

    DB:3.69:Re: Abstract Class kx


    Please help me

    DB:3.69:Re: Abstract Class kx

    I think the abstract superclass should look like this,
    public abstract class Shape {
    abstract double getArea();
    abstract double getPerimeter();
    abstract void draw();
    }It defines in an abstract way some aspects of a Shape. It's got an area, a perimeter and a physical outline which can be drawn.

    Then you can define many different concrete subclasses. What they all have in common is that they abide to the concept of a shape as beeing defined by the Shape class. For example a Rectangle,
    public class Rectangle extends Shapes{
    private double length;
    private double width;

    public Rectangle(double l, double w) { // constructor
    length = l;
    width = w;
    }
    public double getArea( ) { // area of a Rectangle
    return length*width;
    }
    public double getPerimeter() { // perimeter of a Rectangle
    return 2.0*(length + width)
    }

    public void draw() { // shape of a rectangle
    }
    } // RectangleNow you define e few more Shape subclasses like for example a Circle and a Triangle. Finally you let the user pick one and depending on which one got selected you ask follow up questions like width and height if it's a Square. When you have that information you can create the appropriate object assign it to a Shape variable and call the draw method.

    The whole purpose of this excecise is to see that you can treat any subclass (Circle, Triangle or Rectangle) as beeing of the superclass type namely Shape, like
    Shape s = Rectangle(1.0,2.0);
    s.draw(); // correct draw method is called
    s = Circle(3.0);
    s.draw(); // still the correct draw method is called

  • RELEVANCY SCORE 3.62

    DB:3.62: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:3.62: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 3.62

    DB:3.62:Re: Abstract Class And Class x7


    Thanks for ur answer. Where can i get language spec?

    DB:3.62:Re: Abstract Class And Class x7

    realhero wrote:
    Thanks for ur answer. Where can i get language spec?You don't want the JLS for this. Buy an introductory Java textbook or study some online tutorial like this,

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

  • RELEVANCY SCORE 3.57

    DB:3.57: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 3.56

    DB:3.56:Difference Between Abstract Class And Interface 71


    Here is a fresher in Java. Could any body tell me the difference between Abstract Class and Interface. And suppose Abstract class has three methods, in those, two of them are Abstract and one is normal method, and it has been implemented in that class itself. If we extend the Abstract class to our class, do we need to over ride or implement all the methods that are there in the Abstract class or we need to implement only those methods that have been declared as abstract. If it is so, then what is the purpose of implementing non abstract method in the Abstract class.

    Sravan

    DB:3.56:Difference Between Abstract Class And Interface 71

    public abstract class TestAbstract {
    public abstract void method1();
    public abstract void method2();
    public static void method3() {
    // non-abstract method must have a body
    }
    }

    public class TestAbstract2 extends TestAbstract {
    public void method1() {
    // Does not work:
    // Object test = new TestAbstract();
    TestAbstract.method3();
    }
    public void method2() {
    }
    }- you will have to implement all method which are declared as abstract. you do not need to implement method3 in this example., only method1 and method2.
    - an abstract class cannot be instantiated (doesn't work: Object test=new MyAbstractClass())
    - a non-abstract method in an abstract class can be used, if it's a static member.
    - with "extends" you can only have one class, and your class will inherit the members of the superclass
    - with "implements" you can use multiple interfaces, which are only a description of what you have to write yourself...

  • RELEVANCY SCORE 3.56

    DB:3.56:Difference ???? xz


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

    DB:3.56: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 3.54

    DB:3.54:Java Programming 33


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

    DB:3.54: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 3.54

    DB:3.54: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 3.54

    DB:3.54:Re: Casting To An Abstract Class From A Different Classloader ak


    ...and my custom class loader loads Special, and that is why
    I can't then cast Special to it's abstract base class. So there is no way that Base gets loaded by your class loader?

    So your example should look like this:

    Class.forName("Base"); // To make sure it is loaded.

    URLClassLoader loader = new URLClassLoader(codebase, null);
    Class childClass = loader.loadClass(className); // Not base but child
    Base baseObj = (Base)childClass.newInstance();

    DB:3.54:Re: Casting To An Abstract Class From A Different Classloader ak

    I did read that there could be performance problems using reflection but for the sake of simplicity I think I will go down that route.

    Thanks for all your help.

    Jim

  • RELEVANCY SCORE 3.53

    DB:3.53:Difference j9


    difference between abstract class and interface

    DB:3.53:Difference j9

    @OP You can see by the blatant obviousness and boring repetitiveness of these answers that this is a frequently asked question.

  • RELEVANCY SCORE 3.47

    DB:3.47:Difference Between Interface And Abstract Class zm


    What is the differrence between an abstract class and an interace? and when would you use one over the other?

    DB:3.47:Difference Between Interface And Abstract Class zm

    What is the differrence between an abstract class and
    an interace? and when would you use one over the
    other?To (over-)summarise:
    An interface defines what you want to do, but doesn't tell you how to do any of it.
    An abstract class may define some of how to do it, but not necessarily all.

    RObin

  • RELEVANCY SCORE 3.47

    DB:3.47:Inter Face And Abstract Class c3


    hi
    can u please tell me the difference between interface and an abstract class? In which situations they will be usefull.
    thank u
    shyam

  • RELEVANCY SCORE 3.47

    DB:3.47: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:3.47: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 3.47

    DB:3.47:What Is The Difference Between Abstract And Normal Class k1


    What will be the difference if I replaced :
    public abstract MyWork {
    ....
    }
    [/code]

    by public MyWork { ........
    }

    THanks in Advance

    Tleis

    DB:3.47:What Is The Difference Between Abstract And Normal Class k1

    To clear all that up for those guys:

    An abstract class must be subclassed or instantiated as an anonymous class. It can have any of the same members as a regular class and in addition it can define abstract methods. Any abstract methods must be implemented by the subclass or else that class too must be declared abstract.

    An abstract class is different from an interface. Java gives you only a single ancester in your class hierarchy. You will force an implementation to become a descendant of your abstract class -- and therefore no other. In "object oriented programming", the term "an 'is-a' relationship" is used to describe that relationship between any subclass and its superclass. However you like to put it: this is the relationship you will be defining when you write your abstract class.

    - Steev.

  • RELEVANCY SCORE 3.46

    DB:3.46: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:3.46: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 3.46

    DB:3.46: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:3.46: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 3.46

    DB:3.46:What Is The Difference Between An Abstract And An Interface Class? pk


    can anyone enlighten me on this, what is the difference between an interface and an abstract class? When should i use an interface instead of a class and vice-versa? thanks!

    DB:3.46:What Is The Difference Between An Abstract And An Interface Class? pk

    public class Test extends MyClass implements MyInterface {
    public Test() {
    someAbstractMethod();
    someInterface();
    someMethodInAbstractClass();
    super.someMethodInAbstractClass();
    }
    public static void main(String[] args) {
    Test foo = new Test();
    }
    public void someAbstractMethod() {
    System.out.println("someAbstractMethod() in Test");
    }
    public void someInterface() {
    System.out.println("someInterFace() in Test");
    }
    // public void someMethodInAbstractClass() {
    // System.out.println("someMethodInAbstractClass() in Test");
    // }
    }

    abstract class MyClass {
    public void someMethodInAbstractClass() {
    System.out.println("someMethodInAbstractClass() in MyClass");
    }
    public abstract void someAbstractMethod();
    }
    interface MyInterface {
    public void someInterface();
    }Run once, uncomment code, run again, compare output

  • RELEVANCY SCORE 3.46

    DB:3.46: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:3.46: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 3.46

    DB:3.46: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:3.46:Interface Vs Abstract Class 81

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

  • RELEVANCY SCORE 3.46

    DB:3.46: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:3.46: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 3.46

    DB:3.46:Re: Abstract Class And Interface 81


    You should never, ever, ever, ever use abstract classes. NEVER!

    You should always program to interfaces.

    So sayeth the uj.

    Like OMG, HTH, TTYL.

    DB:3.46:Re: Abstract Class And Interface 81

    georgemc wrote:
    filestream wrote:
    You should never, ever, ever, ever use abstract classes. NEVER!

    You should always program to interfaces.

    So sayeth the uj.

    Like OMG, HTH, TTYL.Apart from when I say that, in which case she seems obliged to take the opposite stance. Seriously, recently she was both arguing for and against preferring composition over inheritance in two threads simultaneously, simply in order to gainsay my points. Quite bizarre behaviour, albeit quite revealingRight. That's what I was referring to.

  • RELEVANCY SCORE 3.45

    DB:3.45: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 3.44

    DB:3.44: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:3.44: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 3.44

    DB:3.44:Help Pls! 87


    Hi, can someone pls tell me what the difference between a normal class and an 'abstract class' is.

    Thanx!

    DB:3.44:Help Pls! 87

    Chris Evans just rang to call it off, apparentley he'd rather be seen with someone cool like Danny Baker and that my wife was too old for him.
    So I'll knock up a quick batch of proper nosh and meet yer all there. Hope you all like Pie and Mash Suchi, beautiful.

    Jamie

  • RELEVANCY SCORE 3.42

    DB:3.42:Re: Different Between Abstract Class And Interface 77


    any one can please tell me Difference between
    abstract class and interface. From a typing perspecitive there's no difference (you can declare variables of both). The only difference in principle is that an abstract class also can have concrete methods so it allows you ti inherit implementation along with the type. You can only inherit from one class but from as many interfaces you whish.

    Which one is best ?The short answer is that interface is best.

    DB:3.42:Re: Different Between Abstract Class And Interface 77

    Hi,please kindly help meWell, maybe if you'd post an actual question...

  • RELEVANCY SCORE 3.42

    DB:3.42:Re: Generic Class jp


    user12032283 wrote:
    in this line this.label = new LabelV(value); i get Cannot instantiate the type LabelBecause Label is abstract. You can only instantiate concrete classes. So either make Label non-abstract, or subclass it, implement any abstract methods, and instantiate that.

    Why did you declare it abstract in the first place?

    DB:3.42:Re: Generic Class jp

    So, exactly what problem are you having? I already told you the answer. Are you still confused about something?

  • RELEVANCY SCORE 3.38

    DB:3.38: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:3.38: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 3.35

    DB:3.35:Interfaces And Abstract Classes ck


    Hello,

    I am confused between an Interface and an abstract class. I would cite an example:

    I consider various shape objects esp. square, rectangle etc. and consider a common behavior area which I need to determine for each of these shapes. Should I consider an Interface or an abstract class and why?

    DB:3.35:Interfaces And Abstract Classes ck

    Hint: Interfaces say what objects must do; abstract classes say (partially) how to do them (i.e., it can provide implementations).

    Two shapes are circles and squares.

    To what extent do you think you'll reuse an area() calculation between them?

  • RELEVANCY SCORE 3.35

    DB:3.35:Java Interfaces And Abstract Classed fc


    what is the difference between interface and abstract class?

    DB:3.35:Java Interfaces And Abstract Classed fc

    I suggest you try writing some code and see.

  • RELEVANCY SCORE 3.31

    DB:3.31: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:3.31: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.

  • RELEVANCY SCORE 3.31

    DB:3.31:Re: Abstract Data Type a3


    A class that itself can't be instatiated, but provides properties and behaviors to classes that inhereit from it. Basically, by declaring a class as abstract you are simply stating that the class in question should never be instantiated and by using "abstract" you are guaranteeing it.

    DB:3.31:Re: Abstract Data Type a3

    That means -if i understand right, that an ADT in java is a class, that doesn't however has to be declared "abstract" necessarily. Is that right?

  • RELEVANCY SCORE 3.31

    DB:3.31:Interfaces And Abstract Classes fk


    hi,

    Can anyone help me regarding the difference between interfaces and abstract classes. What is the advantage of interface over abstract classes and viceversa. Obout the possibities of multple inheritance I know. I found allmost all people are talking some external answers.
    Why an abstract class cant we do it with concrete class.
    regards,

    Jayaprasad Viswanathan

    DB:3.31:Interfaces And Abstract Classes fk

    Abstarct class can never be instantiated. Same as interfaces.

    Can be
    subclassed.Same as interfaces.

  • RELEVANCY SCORE 3.29

    DB:3.29:What Is Difference Between Abstraction And Abstract Class ? j3


    What is difference between abstraction and abstract class ?

  • RELEVANCY SCORE 3.29

    DB:3.29:Abstract Classes And Interfaces kp


    I am kinda new to Java but have been studying frequently. I have a question that is probably very simple: What is the difference/advantage between an abstract Class and an Interface?

    DB:3.29:Abstract Classes And Interfaces kp

    Search the forum. Here's a topic that addresses it:
    http://forum.java.sun.com/thread.jsp?forum=31thread=273324

  • RELEVANCY SCORE 3.28

    DB:3.28:Re: Method Local Abstract Inner Classes cf


    I forgot to mention that the above code compiles and you can declare a method local inner class as abstract or final.

    DB:3.28:Re: Method Local Abstract Inner Classes cf

    Usages of this kind, I definitely find useful.
    Still, it's not quite the same as the original example: You are extending a top level abstract class locally while the example shows a local definition of an abstract class. Because of the scope restrictions this would only make sense if you intended to define at least two different concrete derived classes within the same local scope (method body) and use them polymorphically. Which - IMHO - would probably compromise much of the intended readability.
    Anyway, it's a nice language feature.

    C U
    Martin

    I personally prefer the local class to anonymous class definitions anyway. I find it more readable. But as you say: Love it or leave it.

  • RELEVANCY SCORE 3.28

    DB:3.28:Difference B/W Abstract Class And Interface mf


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

    Thanks in advance!

    DB:3.28: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 3.28

    DB:3.28:Re: Difference Between Abstract Class And Interface 7k


    See reply #44 and then please find something more useful to do.

    DB:3.28:Re: Difference Between Abstract Class And Interface 7k

    Passionate_Java_Lover_Vijay wrote:
    hi tigers,
    i am very new to java.
    i have a doublt iin collection.
    at wht situation what interface wil be best than other.

    where should i use List Set, Map and all.
    Advance thanks 2 guys who help me.

    Thanks
    ThinkGodJebus. Are you for real? Get a grip will you

  • RELEVANCY SCORE 3.28

    DB:3.28: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:3.28: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 3.28

    DB:3.28:Best Situation That Describe Difference Between Interface And Abstract c7


    Hi, Please tell me the best example or situation where we should choose interface or abstract class?

    DB:3.28:Best Situation That Describe Difference Between Interface And Abstract c7

    Smiley,
    It is the same as about apples and computers.
    An Interface is a contract, it describes what a class should contain to implement it (and can than be used to to get those members of a class whichfulfillthe contract) but an interface contains no actual implementation.
    An Abstract Class is a class itself which can be (only) inherited used as base for another class, the members and properties of a base class can be used likewise the inheriting class.
    Because of above can an Abstract Class implement an Interface, however an Interface cannot implement an Abstract class.

    Success
    Cor

  • RELEVANCY SCORE 3.28

    DB:3.28:Complete Differences 1d


    Hi,
    Please provide me all possible differences between...

    1). Prepared Statement and Callable Statement
    2). Abstract Class and Interface

    Thanks,
    R S

    DB:3.28:Complete Differences 1d

    See this

    http://www.javaworld.com/javaworld/javaqa/2001-04/03-qa-0420-abstract.html

  • RELEVANCY SCORE 3.28

    DB:3.28:Re: Difference Between Abstract Class And Interface. f3


    Thanks, jverd. I have got it.

    George

  • RELEVANCY SCORE 3.26

    DB:3.26:What's The Difference Between Abstract Class And Interface? 1z


    Dear all,
    Can anyone give me some hints about this topic?

    Thanks.

    Leo

    DB:3.26:What's The Difference Between Abstract Class And Interface? 1z

    Also, you can only extend one class, but can implement many interfaces. I extend a class for true is-a relationships, I use implements like mixins.

  • RELEVANCY SCORE 3.26

    DB:3.26:Abstract Class And Constructors s7


    Why is it that Constructors are permitted within an abstract class?

    DB:3.26:Abstract Class And Constructors s7

    Thanks jverd!!You're welcome. But I just added a little detail to the answers that Rene provided.

  • RELEVANCY SCORE 3.24

    DB:3.24:Abstract Class And Interface z1


    What is most important thing about abstract class and interface.

    When to use abstract class and interface.

    DB:3.24: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 3.23

    DB:3.23:Re: What Is The Difference Between An Interface And An Abstract Class? 1a


    8000 views already wow.

    DB:3.23: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 3.21

    DB:3.21:What Is The Main Difference Between Interface And Abstract Class 37


    Hi ,

    Please help on this ..

    Regards,
    vij

    DB:3.21:What Is The Main Difference Between Interface And Abstract Class 37

    All the methods declared inside interface should be abstract

    All the methods declared for an interface are abstract, by definition.

    but in case of abstract class at least one method should be abstract

    No. An abstract class is not required to have any abstract methods. It's not even a "should".

    Abstract class must be extended abstract ()
    methods generally contain only declaration part
    without definition part.
    No "generally" about it, as there are no exceptions. Abstract methods do not have a declared body, by definition.

    ~

  • RELEVANCY SCORE 3.21

    DB:3.21:Core Java 83


    what is differernce between abstract class and interface?

    DB:3.21: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 3.21

    DB:3.21:Re: A Small Doubt Regarding Abstract Classes... 7f



    HOWEVER, i was trying to figure out the possibility,
    /or the ramifications of
    allowing a class to EXTEND an
    interface,
    thereby, "inheriting" all the Contract...but since,
    we're NOT implementing...why NOT just mark the class
    as ABSTRACT..so that
    the first CONCRETE class down-the-family-tree...that
    extends this abstract class, will ALSO fulfill the
    CONTRACT which was ..."sort-of-signed by the
    ABSTRACT class....?!?"This is not what I would call an explicit contract fulfillment. By forwarding it to the next class, you basically don't enforce anything. You don't have this problem with inheritance, because inheritance always follows a tree structure, which forces every class in a very strong defined context.

    I have thought now for a couple of different scenarios. Technically, they would all work, although they get nasty here and there. I guess, in the end it's really a language decision to enforce interface fulfillment.

    DB:3.21:Re: A Small Doubt Regarding Abstract Classes... 7f

    Hi ppl..

    Why can't an Abstract class extend an
    Interface It can implement an interface, which is the same thing. Implements and extends both specify type inheritance in Java, and they're simply used in mutually exclusive cases. The rules of the language simply say to use one word for certain cases and the other word for the other cases. It could have just been on single word and everything would work the same way it does now. If an abstract class could extend an interface, it wouldn't mean anything different than implementing it.

  • RELEVANCY SCORE 3.21

    DB:3.21:Difference Between A Abstract Class With 4 Abstract Methods And A Interface With 4 Abstract Methods. 8c


    what is the difference between Difference between a Abstract class with 4 abstract methods and a Interface with 4 abstract methods.

    DB:3.21:Difference Between A Abstract Class With 4 Abstract Methods And A Interface With 4 Abstract Methods. 8c

    Your question is better rephrased as: What is the difference between an abstract class and a interfase?
    This has been discused here
    http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/67451957-f0bd-4b9b-a2c0-16f604ce8643
    Regards

  • RELEVANCY SCORE 3.21

    DB:3.21: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:3.21: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 3.21

    DB:3.21: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 3.20

    DB:3.20: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:3.20: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 3.18

    DB:3.18:Interface Vs Abstract Class d8


    when do we need interface and when abstract class?

    DB:3.18: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 3.18

    DB:3.18: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:3.18: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 3.17

    DB:3.17:Difference 7x


    Hi sirs,
    Give me the main differences between abstract class and interface.Dont give me the links sir,

    when we go to use for the interface and for abstract class in developing an application

    DB:3.17:Difference 7x

    Another link:
    {color:#0000ff}http://forum.java.sun.com/thread.jspa?messageID=9961601{color}

    db

  • RELEVANCY SCORE 3.17

    DB:3.17: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:3.17:Abstract Class And Interface???? ja

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

  • RELEVANCY SCORE 3.16

    DB:3.16:Subclass Vs Concrete Class fs


    Hi,

    What is the exact difference between subclass and concrete class?

    What is the need in subclassing abstract class to again abstract class?

    Thanks in Advance,
    venu.

    DB:3.16:Subclass Vs Concrete Class fs

    Hi,

    U mean to say Concrete classes are instantiatable
    and every concrete class is a subclass of some
    super class.Plz clarify me if i am wrong.That's correct. But it's also true that every class--both concrete and abstract--is a subclass of some superclass, except Object which has no superclass.

    NOTE: The following is simply provided in the interest of completeness because I'm a ballsniffing pedant. It's not that important to what you're asking about, and may just cause more confusion. Feel free to ignore it.

    Also, it's possible to make a concrete class non-instantiable by having a single private constructor and throwing an exception from it, but that's a runtime issue--the compiler will let you insstantiate the class (only from within itself if the c'tor is private).

  • RELEVANCY SCORE 3.16

    DB:3.16: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:3.16: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 3.15

    DB:3.15: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:3.15: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 3.15

    DB:3.15:Difference Between Abstract Class And Interface ? fz


    CAN ANY BODY TELL ME THE DIFFERENCE BETWEEN THE ABSTRACT CLASS AND INTERFACE ?

    DB:3.15:Difference Between Abstract Class And Interface ? fz

    - An abstract class is a class that can not be instantiated but that can contain code, i.e. it gives you the ability to specify default implementations of methods.

    - An interface only contains methods but does not contain any code and you need to implement all the methods defined in the interface.
    - Interfaces may be multiple-inherited, abstract classes may not
    http://www.codeproject.com/Articles/11155/Abstract-Class-versus-Interface
    http://stackoverflow.com/questions/56867/interface-vs-base-class

  • RELEVANCY SCORE 3.15

    DB:3.15:Why We Use Interface? c9


    I appeared one of my interviews.The Interviewee asked me a question that

    Suppose one is abstract class and one is interface.
    All the methods of abstract class are abstract.
    Then on this level what is the difference between abstract
    and interface and why we use interface. I could not answer properly.
    Please guide me the actual difference between Abstract class and Interface.
    Thanks

    DB:3.15:Why We Use Interface? c9

    google is your friend! Dear You are also my friend ;)

  • RELEVANCY SCORE 3.14

    DB:3.14:Re: Abstract Class With All Abstract Methods Is Same As Interface ?. ff


    kogose wrote:
    this looks ambiguous to me?Have you tried it? The compiler will tell you that it's ambiguous and won't let you compile it.

    DB:3.14:Re: Abstract Class With All Abstract Methods Is Same As Interface ?. ff

    An abstract class with all abstract method is not equal to an interface.

    An abstract class is just like any other class, only that it cannot be instansiated. In order to use the methods and data, it has to be extended.
    An interface on the other hand, defines a set of prototype.

    If i knw what interface you are implementing, i dont have to know what code you have written in the function. It is more like standardising. But when you write an abstract class, and i am using it, in future you may change its contents and add things that is not necessary for my program. An interface implemented, helps the other programmer to know how to access a perticular functionality of a class.

    For example, if i want to access a functionality draw() from your class, say circle, i just have to knw its signature. If you are using an interface and implementing the function of that interface, in future you cant change the signature of the function (can change the content thou) . But when it comes to abstract class, you can overload and override, in which case you may change the signature (as you have the descrition), and my program may no longer be able to use your draw() function. Thus, consistency is questioned. Interface avoids such a problem.

  • RELEVANCY SCORE 3.14

    DB:3.14: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:3.14:Difference Between Pure Abstract Class And Interface? 89

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

  • RELEVANCY SCORE 3.14

    DB:3.14:Abstract Class And Interfaces jf


    Hi,

    In which senarios, we can choose abstract class and interfaces

    Thanks

    DB:3.14: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 3.13

    DB:3.13: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:3.13: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 3.13

    DB:3.13:Abstract Class 71


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

    DB:3.13: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 3.13

    DB:3.13:Re: Abstract Classes ja


    abstract class with 2 abstract methods

    first method is an iterative solution to a problem
    abstract void solveIter(int[] a, int first, int last);second is the recursive solution
    abstract void solveRec(int[] a, int first, int last);i have 8 derived classes representing 8 different types of problems

    each derived class can solve it using the iterative or recursive method that i complete in each class

    however say 2 of the classes will only support either the iterative or recursive method only

    in this case i want to throw an UnsupportedOperationException

    DB:3.13:Re: Abstract Classes ja

    Like this:
    import java.util.*;

    interface Sorter {
    //lo = hi. Method sorts v[lo]...v[hi-1]
    void sort(int[] v, int lo, int hi);
    }

    class QuickSort implements Sorter {
    private static final int CUTOFF_SIZE = 16;

    private Sorter smallSorter;

    public void setSmallSorter(Sorter smallSorter) {
    this.smallSorter = smallSorter;
    }

    public Sorter getSmallSorter() {
    return smallSorter;
    }

    public void sort(int[] v, int lo, int hi) {
    Sorter smallSorter = getSmallSorter();
    if (hi-lo = CUTOFF_SIZE smallSorter != null) {
    smallSorter.sort(v, lo, hi);
    } else {
    Arrays.sort(v, lo, hi);
    //cheating for the sake of example
    }
    }

    //sample main
    public static void main(String[] args) {
    int[] data = ...;
    QuickSort qs = new QuickSort();
    qs.setSmallSorter(new InsertionSorter());
    qs.sort(data, 0, data.length);
    System.out.println(Arrays.toString(data));
    }
    }

  • RELEVANCY SCORE 3.12

    DB:3.12:Interface And Abstract Class c8


    Hi,

    Could you please let me know what is the exact difference between interface and abstract class.Which one is better to use .Could you please give me indepth answer.

    DB:3.12:Interface And Abstract Class c8

    Stop. Stop. Stop. I beg you...You're behaving like a Chinese gentleman with sand in his boots. Stop.

    Do we save the execution time by using interface.This is a compiler/byte code related question. Please post it in the proper place.

    What might be the behaviour inside the memory
    location by using interface and abstract class.Same answer.

    /Morten

  • RELEVANCY SCORE 3.12

    DB:3.12: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:3.12: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 3.12

    DB:3.12:Combining Inheritance And Static Methods aj


    Hello all

    I have a question regarding the combination of inheritance and static methods. My endgoal is to create a user friendly way of writing programs using code I'm writing. Therefor I wish to have static methods so that the user can write code like this:

    public static void main () {
    SearchTable.doubleClick();
    ListTable.doubleClick();
    }

    Since the way you perform a doubleClick is always the same, I wish to abstract this logic inside a parent class:
    public abstract class AbstractTableLogic{
    public static void doubleClick() {
    Table table = new Table();
    table.waitFullyLoaded();
    table.doubleClick();
    }
    }

    The only thing different between the specific table classes is the way you retrieve the table. So this logic will be put inside the specific table classes:
    public class SearchTable extends AbstractTableLogic{
    public Table getTable() {
    return new Screen().getSearchArea().getTable();
    }
    }

    public class ListTable extends AbstractTableLogic{
    public Table getTable() {
    return new Screen().getListArea().getTable();
    }
    }

    Since the screen is always changing, I want to have the latest table visible on the screen. Therefor the logic performed in the abstract class should use this specific table. I want to do something like the following, but I'm not able (access of non-static member from within a static method):
    public abstract class Table{
    public abstract Table getTable();

    public static void doubleClick() {
    Table table = getTable();
    table.waitFullyLoaded();
    table.doubleClick();
    }
    }
    This way the way the table is retrieved would remain specific to the implementation and the clicking logic could be abstracted. Unfortunately this is not possible.
    As a temporary solution I already came up with the following:
    - make all the methods non-static
    - write a wrapper class which makes the methods static:
    public class SearchTableUIClass {
    public static void doubleClick() {
    SearchTable table = new SearchTable();
    table.doubleClick();
    }
    }

    This implementation works, but I would prefer a way to not have to re-write all the methods inside a wrapper class to make them static.

    Thanks in advance!

    DB:3.12:Combining Inheritance And Static Methods aj

    You could work around this by defining a static variable in the abstract class for a Table, then creating a static method for doClick() that acts upon this variable. However you will need to implement methods in each class to set the Table to its appropriate value, then call this method prior to calling doClick(). Pretty ugly huh?

    Mel

  • RELEVANCY SCORE 3.12

    DB:3.12:Re: Interface Vs Abstract Class 1d


    Abstract classes have the significant advantage that you don't have to change each and every implementation if you add a new method with a sensible default implementation.

    DB:3.12:Re: Interface Vs Abstract Class 1d

    You cannot tighten a screw with a hammer. You break
    the threading, and it will remain loose.But it's very hard to hit broken things repeatedly in a satisfying manner with a screwdriver in such a way that the thing in question is not recognizeable as what it was to begin with. Granted, it's possible but rather hard to do with a screwdriver ;-)

  • RELEVANCY SCORE 3.11

    DB:3.11:Downcasting Abstract Class. cc


    problem goes like this. I have and abstract class A[which extends Thread ] and three another classes B,C,D extending from this Abstract class A.

    In the main class at runtime,I will be getting the class name[B or C or D] to be instantiated. Also newInstance() of Class cannot be called as the Constructors for the classes B ,C ,D are different from the default.

    Can anyone suggest a wayout.

    DB:3.11:Downcasting Abstract Class. cc

    In the main class at runtime,I will be getting the
    class name[B or C or D] to be instantiated. Also
    newInstance() of Class cannot be called as the
    Constructors for the classes B ,C ,D are different
    from the default.

    Can anyone suggest a wayout.Erm, you haven't actually asked a question - what is the problem?

    Assuming that you want to instantiate a class whose name you don't know until runtime (though I don't see what this has to do with the title of the topic), then you can use Class.getDeclaredConstructor or Class.getDeclaredConstructors and then Constructor.newInstance

  • RELEVANCY SCORE 3.11

    DB:3.11:Diff Between Abstract Class And Final Class dk



    hi,

    I want to know diff between abstrect class and final class.

    Thanks in advance.

    Regards,

    Agalya

    Edited by: agalya devi on May 29, 2008 12:23 PM

    DB:3.11:Diff Between Abstract Class And Final Class dk


    Abstract class can have both abstract or nromal methods. These cannot be instantiated ie we cant create any instance of this class. Here we cant have implementation for abstract methods. We need to inherit this class in tonother then provide the implementation.

    As we can chain upto N levels in inheritance, ie mutlilevel, If we want to stop the further drill down of the inheritance tree. We need to stop the inhertiance from going further, we go for Final class.

    If a class is declared as Final, then i cannot be inherited further. Likewise, if a method is declared as final, then it cant be over ridden ie we cant provide any implementation or it cannt be redefined.

    Encourage me by rewarding points.

    Regards

    Chandralekha

    Edited by: Susheela Chandralekha on Jun 24, 2008 8:46 AM

  • RELEVANCY SCORE 3.11

    DB:3.11:Re: Which One Is The Best And Why cs


    But implementing interface is generally more
    difficult than extending (abstract) class, because
    (abstract) class provides more things than
    interface.For a start that is wrong, it depends on the interface/abstract class.

    Secondly implementing is not relivent at all to this.

    DB:3.11:Re: Which One Is The Best And Why cs

    I think when ,
    A obja = new B();
    is used the instance variable and methods will
    not be accessible evia obja.Correct.

    B obja = new B();
    is used the instance variable and methods can
    be accessed via obja , which may involve bit more
    memory usage than the previous case .So its betterUtter BS, sorry. The object still is an instance of B.

    to go for the last case if v dont need B instance
    members not to be accessed.That doesn exist.

    and also if A is implemented by many classes
    in the ejb for bussiness logic purpose , only the
    interface is sent back as return value hiding the
    concrete class (Encapsulation)That is generalization or abstraction, not encapsulation.

    .obviously cannot have
    the concrete class with definition in the calling
    end.Huh?

  • RELEVANCY SCORE 3.11

    DB:3.11:Re: Abstract Class 81


    georgemc wrote:
    jverd wrote:
    georgemc wrote:
    YoungWinston wrote:
    georgemc wrote:
    Scorpiongiri wrote:
    yesActually, if you want to give a simple yes/no answer to the original question, the correct answer would be "no", since, by definition, a concrete class cannot be declared using the 'abstract' keywordI'll pitch in for Scorpiongirl here. According to OP's initial question, the answer is 'yes'. Arguing about Java semantics, while important, is secondary.I'm not talking about Java semantics, and I respectfully disagree that this is secondary. Although there is a Java keyword abstract, the concepts of abstract and concrete in this context are not specific to Java, or even software engineering. The OP needs to know that something concrete cannot also be abstract. Sure, the answer to the first question is "yes", but as qualified by the second question, the OP clearly misunderstands what concrete class means. Answering one question whilst ignoring the other is misinformingSo, your definition of "abstract" is "contains at least one abstract method," rather than "is declared abstract"?Nope. Where do I imply that? " the concepts of +abstract+ and +concrete+ in this context are not specific to Java, or even software engineering. The OP needs to know that something concrete cannot also be abstract."

    I assumed your concrete/abstract definitions for this context were based on the presence or absence of unimplemented methods. If that's not it, what is it? Clearly it can't be "declared abstract", since obviously a fully implemented class can be declared abstract.

    Can I have an abstract class in which all the methods are defined. I mean can i make a concrete class (which has all it's methods well defined ) preceded by the abstract keyword.Answer: yes and no, respectivelySo, for the first one, what is your definition of "abstract class"? Above you say that it's NOT that the class contains at least one abstract method, so, what kind of class in Java is abstract, other than "one which has at least one abstract method"?

    DB:3.11:Re: Abstract Class 81

    YoungWinston wrote:
    georgemc wrote:
    Answer: yes and no, respectivelyWhich leaves the OP no better off than when s/he started. How about this:
    In answer to your question: yes; however you are misusing the word 'concrete' as understood by Java programmers.Good point. Best go tell ScorpionGirl

  • RELEVANCY SCORE 3.11

    DB:3.11: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:3.11: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 3.11

    DB:3.11:When To Use Abstract Class And Interface? jp


    hi,

    When to use Abstract class and Interface?

    DB:3.11: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 3.11

    DB:3.11:Concrete Class ff


    Hi

    Could someone tell me what the difference is between an abstract class, interface class and a concerte class. Cant figure it out.

    Thank you
    David

  • RELEVANCY SCORE 3.09

    DB:3.09:Abstract Class Vs Interface sc


    can anyone pls help me in understanding difference between an interface and an abstract class which has no function with implementation

    which is better abstract cls or interface in term of speed, features..?
    Thanksbahushekh

    DB:3.09:Abstract Class Vs Interface sc

    To Mike Feng or any other moderator,
    Can you unmark
    as answer the previous post from myself please?
    Reason: It has no relevance to the original question, I was just replying to the post preceding it from RudeDog2
    which I also feel, does not really relate to the original question.
    I will leave it to Rudy to decide if He wants that post to be unmarked.

    Regards,

    John

    Click this link to see how to insert a picture into a forum post.

  • RELEVANCY SCORE 3.09

    DB:3.09:What Is The Difference Between Abstract Class And Interface jf


    Hi,
    Can you please tell me the differences between Abstract class and Interface.
    In which scenarios we have to use Abstract class and in which scenarios should use Interface.

    Thanks and Regards
    Kranthi

    DB:3.09:What Is The Difference Between Abstract Class And Interface jf

    http://stackoverflow.com/questions/761194/interface-vs-abstract-class-general-oo

  • RELEVANCY SCORE 3.09

    DB:3.09:Difference Between Abstract Class And An Interface c3


    hi all,

    what is the difference between an ABSTRACT CLASS with full of METHOD DEFINITIONS and no implemented methods. AND an interface having the same definitions.

    In which situation we use abstract class and in which situation we use interface.

    what are the benefits.

    Can anybody explain it clearly.

    bye
    -hari

    DB:3.09:Difference Between Abstract Class And An Interface c3

    http://www.google.com/search?q=java+difference+abstract+interfaceTrying to teach a man to fish, are you?

  • RELEVANCY SCORE 3.08

    DB:3.08: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:3.08: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 3.08

    DB:3.08:Re: Abstract Class Vs Interface Difference jc


    While this is by no means complete, the major
    differences between an interface and an abstract
    class with all abstract methods is that you don't
    have to create an implementation for the abstract
    methods in a class that extends the abstract class.Yes you do; unless the extending class is also abstract.

    You do have to implement all methods in an
    n interface. Also you can use access modifiers other
    than public in an abstract class, while interface
    methods must always be public. public or package-private?

    If you don't know why either of these things would be useful then you
    probably don't care, and could just use an interface.And seeings as people are answering here desipte the laziness; abstract classes can also have implemented methods, and member variables. Interfaces cannot.

    DB:3.08:Re: Abstract Class Vs Interface Difference jc

    While this is by no means complete, the major
    differences between an interface and an abstract
    class with all abstract methods is that you don't
    have to create an implementation for the abstract
    methods in a class that extends the abstract class.
    You do have to implement all methods in an
    n interface. No.

    The rules for what must be implemented are the same regardless of whether it's a class or an interface.

  • RELEVANCY SCORE 3.08

    DB:3.08:Help With Interface And Abstract cs


    Hi all

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

  • RELEVANCY SCORE 3.08

    DB:3.08:Re: What Is Abstract Class And Abstract Data Type!!! 8c


    hello kayaman,

    thanks for telling this....
    i think you should not waste your time in writing this as u seems too busy.......

    DB:3.08:Re: What Is Abstract Class And Abstract Data Type!!! 8c

    Unless you're making a point that sailed right over my
    head, dearest Uj, I must beg to differ. In java, an
    abstract class allows method implementation, while an
    interface does not.Okay, I think there's a slight conceptual difference but let me rephrase my answer to the OP. The main differences between abstract classes and interfaces are,

    1. An class can extend one abstract class only, but it can implement many interfaces.

    2. An abstract class can be partially implemented while an interface can contain no implementation at all.

    I think this view will make me better prepared for the certification exam -:)

  • RELEVANCY SCORE 3.07

    DB:3.07:Abstract Class And A Static Method a1


    Can i call a static method within an abstract class ?

    DB:3.07: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 3.07

    DB:3.07:Re: Nested Classes kx


    public abstract class pascalPlugin {
    public abstract class argsObject {
    public argsObject(ArrayListpascalType arrayOfArgs) {
    Class thisClass=this.getClass();
    //logic here
    }
    public boolean argsMatch() {
    //logic here
    }
    }
    }is the class, and i try to access it by
    pascalPlugin foundPlugin =getUnknownClassWhichExtendsPascalPlugin();
    boolean b=foundPlugin.new argsObject(null).argsMatch();CodeProcessor.java:115: processing.pascalPlugin.argsObject is abstract; cannot be instantiated

    DB:3.07:Re: Nested Classes kx

    exept, you can NOT have an implementation of an
    abstract class (which foundPlugin) is without an
    implementation of all it's subclasses (such as
    argsObject) You're mistaken in a couple of ways here.

    First, a nested class is not the same as a subclass.

    Second, a concrete class must have implementations for all its methods, but it can still have an abstract nested class.

    Third, you can have an instance of a concrete class that has abstract subclasses. Object is concrete and has many concrete subclasses. Classes don't know anything about their subclasses.

    This compiles.
    public abstract class AbOut {
    public abstract class AbIn { public abstract void bar(); }
    }

    public class ConcOut extends AbOut {
    public abstract class AbIn2 { public abstract void foo();}
    }foundPlugin MUST have an implementation
    of argsObject, according to the rules of java,And you think this because...?

    You read it in the JLS? Citation please.

    You tried to compile and it failed? My sample above demonstrates the countereample. If I'm misunderstanding what you're talking about, please post an example

    Or maybe you just thought it had to be that way because that seemed the most intuitive and when it wasn't, rather than trying to understand or adjust your thinking, you figured it would be more fun to throw a hissy fit and call Java "stupid"?

  • RELEVANCY SCORE 3.07

    DB:3.07:Simple Query ac


    Difference between Abstract class and interface with practical example

    DB:3.07:Simple Query ac

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

  • RELEVANCY SCORE 3.07

    DB:3.07:Why Interface?Differnce Between Interface And Abstract Class d3


    why we go for interface? what is the difference between interface and abstract class?

    can anyone plz explain with clear picture.

    DB:3.07:Why Interface?Differnce Between Interface And Abstract Class d3

    Look at his profile. He's nothing but a homework dumper anyway. Someone to be ignored.

  • RELEVANCY SCORE 3.07

    DB:3.07:Re: Inteface Vs Abstract Class dd


    interfaces are implented, abstract classes are extended. In an interface ther is no code or variables only methods and any class that implements the interface must provide code implementation for all the methods. An abstract class has code. Why you would use them i have no idea or i jsut fogot

    DB:3.07:Re: Inteface Vs Abstract Class dd

    Joshua Bloch has something to say about this... see the book "Effective Java" - one of the best Java books once you no longer consider yourself a beginner

  • RELEVANCY SCORE 3.07

    DB:3.07:Good Simple Example Of Difference Between Interface And Abstract Class 83


    Hi All,

    I am new to java...

    I am confused lot about the difference between interface and abstract class....

    Can anybody tell me the difference between interface and abstract class with some good and simple exmple...

    Kindly help me...

    Thanks in advance...

    DB:3.07:Good Simple Example Of Difference Between Interface And Abstract Class 83

    phdk wrote:
    georgemc wrote:
    public class AbstractClassThatIsntAnInterface {

    public abstract void doSomething();
    public abstract void doSomethingElse();

    }Nice naming for a nonabstract class! ;-)

    @OP: read this: [http://java.sun.com/docs/books/tutorial/java/IandI/abstract.html]Er, you, um, spotted my deliberate mistake.....

  • RELEVANCY SCORE 3.06

    DB:3.06: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 3.06

    DB:3.06:Diff. Between Interface And Abstract Class 8j


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

    DB:3.06:Diff. Between Interface And Abstract Class 8j

    An interface is a way to specify a set of abstract methods that you want a class to implement. The big deal is that the compiler will check that the methods are in fact provided by the class.

    Interfaces almost always represent a view that has nothing to do with the class hierarchy. It could for example be a specific way to access data, like an iterator. Iterators have seldom anything to do with the logical class design. It's just a common way to iterate through the elements of any class.

  • RELEVANCY SCORE 3.06

    DB:3.06: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:3.06: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 3.06

    DB:3.06: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.