Why classloader doesnot have abstract methods

Hi
I am looking at ClassLoader source code from src.zip under jdk1.5
I see the ClassLoader class definition as abstract but none of the methods are declared as abstract. Why findClass is not an abstract method?
Am I looking at something wrong?
Or
Is this designed purposefully ?
Thanks in advance
-Tumu

Why findClass is not an abstract method?Because it has a default implementation, as defined by ClassLoader.
Am I looking at something wrong?No.
Is this designed purposefully ?Yes. Classes may be declared abstract that have no abstract methods. This is perfectly legal.

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

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hi folks,
i facing issue for ABSTRACT Class.
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Hello Arshad,
Create a class(ZABSTRACT) and make its type as Abstract( Which means atleast one of its methods is abstract)
We can have abstract classes with all it's methods as non-abstract or concrete. A small example is given below:
CLASS gcl_abstract DEFINITION ABSTRACT.
PUBLIC SECTION.
    METHODS concrete. "Concrete
ENDCLASS.                    "gcl_abstract DEFINITION
*       CLASS gcl_abstract IMPLEMENTATION
CLASS gcl_abstract IMPLEMENTATION.
METHOD concrete.
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ENDMETHOD.                    "concrete
ENDCLASS.                    "gcl_abstract IMPLEMENTATION
*       CLASS gcl_abstract_sub DEFINITION
CLASS gcl_abstract_sub DEFINITION INHERITING FROM gcl_abstract.
PUBLIC SECTION.
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ENDCLASS.                    "gcl_abstract_sub DEFINITION
*       CLASS gcl_abstract_sub IMPLEMENTATION
CLASS gcl_abstract_sub IMPLEMENTATION.
METHOD concrete.
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ENDCLASS.                    "gcl_abstract_sub IMPLEMENTATION
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Although i will agree there is no point in making a class as abstract & having no abstract method
@Sri: Looks like you're trying to implement the abstract method "AREA" in the abstract class hence the error. For abstract method you cannot define their implementation in the corres. abstract class.
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Edited by: Suhas Saha on Mar 30, 2011 12:04 PM

Abstract methods in interface?

hi, i dun feel that an interface can have abstract methods although the compiler doesn't complain. but i still see developer declares abstract methods in the interface. any clarification on this? thx
cy

hi, i dun feel that an interface can have abstract
methods although the compiler doesn't complain. but i
still see developer declares abstract methods in the
interface. any clarification on this? thx
cyThose developers are just a bit verbose, all methods in an interface are public and abstract.
Kaj

Why java does not force to declare atleast one abstract method

hi,
i can define an abstract class without declaring any abstract method in that class. But why wud i do this ? i mean when i have decided that a particular class should be inherited by other subclass and subclass should porvide implementation then there should be atleast one method in the abstract super class which requires implementation.
All i want to know is why java does not force to declare atleast one abstract method in abstract class.
there may be some situations where this restriction can create problem if it is like that then can anybody give some example.
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hi,
i didn't get u.
u r trying to say that i have an abstract class with
only static methods then my questions is why wud
declare such a class as 'abstract' class? because a
static method can't be abstract also. Even then if
somebody want to define such a class with only static
methods then compiler should force him to declare
atleast one abstract method which can be implemented
by subclass, because as i said before if sumbody
decide to define a class abstract then he wants that
it should be inhereted but as u r saying a class with
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class it can be a simple class.there's no functional reason, really... actually, factory-like classes are often defined the way Ceci described
"abstract" only ensures that nobody can ever get an instance of that class (as a matter of fact, what would be the point of getting an instance, if no instance method exists ?)

Abstract method which when implemented will have different parameters

Hello to all,
I have an assignment but not looking for someone to do it for me. I am only searching for a suggestion on how to do the following.
Imagine having an application that needs to provide an estimate of the rent for different buildings.
Basically I start with by having a class name Building. This class has an abstract method called estimateRent.
I then create two classes that extend the class Building which are named Apartment and House. Both need to have the method estimateRent.
However the problem is that the rent for the Apartment is calculated on the nights passed in the flat and the people in it, while the rent for the House is just calculated on a month bases.
This means the estimateRent method requires to have different parameters depending if it is implemented inside the Apartment class or the House class.
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The first option is to not declare the estimateRent method as an abstract method inside the Building class and just implemented inside the Apartment and House with different parameters. I do not like this option since in the future if a new Building comes in then I would like to impose the fact that that object needs to have a calculate method.
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tx

The implementation changes, yes.Yes that I could understand in the Strategy Pattern (in the document I read it was being compared with the Template Pattern).
Then you need to refactor your design.I tought about that, however if you read my first post you will notice that I have different criteria on which the costs need to be estimated. While the costs for a flat are estimated on the people staying in and nights slept there, the costs for the house are based only on the months stayed there regardless of the people living in. Now for me I feel that it is bad programming practice to create one method that can have all the parameters required for any scenario. I mean the following is NOT something I am going to do:
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What is the "Context" going to have?Yep I agree, but so far my limited brain has only come up with that! I am open to any other sugestion! always if i understand it first!
Basically the Context would better be named as Criteria and it would be an interface as follows:
interface Criteria{}
Then I would create two classes that implement the Criteria object as follows:
class AppartmentCriteria implements Criteria{
public Result estimateCosts(int nights, int people);
class HouseCriteria implements Criteria{
public Result estimateCosts(int months);
Now when I recieve the inputs, depending on the scenario the Criteria is typecasted and the correct parameters passed and we recieve the Result.
I feel the above sucks since I am not seeing it as an object oriented way of doing this out! Is there any other sugestions! The refactoring thing I am intrested in! however really I can not see how such a call to that method could be refectored!
Thank You,
tx.
PS: Sun has blocked my other account as well, and this time they did not even send me an email to confirm that I was registered successfuully :( Is there someone I can contact on this? I guess next time I will reply with tx53m :)

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For example, why i can use this [http://docs.oracle.com/javase/7/docs/api/java/nio/CharBuffer.html#slice] if this is abstract?
Edited by: 947971 on 13-set-2012 10.38

947971 wrote:
Yes, but if CharBuffer has a method declared:
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Reg. oops...implementation of abstract method in se24...have ur ponts..

Hi all,
In SE24 i made an abstract class & made a method abstract successfully.
Now i made another class that inherited my abstract class, it is showing my abstract method there.
Now when i want to give implementation to that method, but when i double click on that system is showing "method is abstract & has not yet redefined".
Pleas let me know..how i implement it..
Thanx in advance..
Have ur point.s

Hi
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 returning value(value) type some type.
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Endclass.
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Priavte section.
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Within the redefined method, you can access components of the direct superclass using the SUPER reference.
The pseudo-reference super can only be used in redefined methods.
reward if usefull

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Why classloader doesnot have abstract methods

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