What is the Use of Abstraction

What is the Use of Abstract class..
Edited by: Deenu on Jul 1, 2008 11:11 PM

Deenu wrote:
What is the Use of Abstract class..It's highly effective in confounding lazy noobs.
Instead of posting every question that pops into your mind and waiting for somebody to spoonfeed you the answer, you might find it useful to go through one or more tutorials or texts on Java. For instane, perhaps one or more of the following might be useful.
Sun's [basic Java tutorial|http://java.sun.com/docs/books/tutorial/]
Sun's [New To Java Center|http://java.sun.com/learning/new2java/index.html].Includes an overview of what Java is, instructions for setting up Java, an intro to programming (that includes links to the above tutorial or to parts of it), quizzes, a list of resources, and info on certification and courses.
[http://javaalmanac.com|http://javaalmanac.com]. A couple dozen code examples that supplement [The Java Developers Almanac|http://www.amazon.com/exec/obidos/tg/detail/-/0201752808?v=glance].
jGuru. A general Java resource site. Includes FAQs, forums, courses, more.
JavaRanch. To quote the tagline on their homepage: "a friendly place for Java greenhorns." FAQs, forums (moderated, I believe), sample code, all kinds of goodies for newbies. From what I've heard, they live up to the "friendly" claim.
Bruce Eckel's [Thinking in Java|http://mindview.net/Books/DownloadSites] (Available online.)
Joshua Bloch's [Effective Java|http://www.amazon.com/Effective-Java-2nd-Joshua-Bloch/dp/0321356683/ref=pd_bbs_1?ie=UTF8&s=books&qid=1214349768&sr=8-1]
Bert Bates and Kathy Sierra's [Head First Java|http://www.amazon.com/exec/obidos/tg/detail/-/0596004656?v=glance].
James Gosling's [The Java Programming Language|http://www.bookpool.com/sm/0321349806]. Gosling is
the creator of Java. It doesn't get much more authoratative than this.

Similar Messages

Why class builder allows to develop abstract final class ? What is the use of such class in ABAP?

I am new to ABAP. I tried creating abstract class and found that class builder allows development of abstract final class. What is the use of such class in ABAP?

Hi,
Does not compile:
This one do:
Inheritance:
Regards.

What is the use of Generic class in java

hi everyone,
i want to know that
what is the use of Generic class in java ?
regards,
dhruvang

Simplistically...
A method is a block of code that makes some Objects in the block of code abstract (those abstract Objects are the parameters of the method). This allows us to reuse the method passing in different Objects (arguments) each time.
In a similar way, Generics allows us to take a Class and make some of the types in the class abstract. (These types are the type parameters of the class). This allows us to reuse the class, passing in different types each time we use it.
We write type parameters (when we declare) and type arguments (when we use) inside < >.
For example the List class has a Type Parameter which makes the type of the things in the list become abstract.
A List<String> is a list of Strings, it has a method "void add(String)" and a method "String get(int)".
A List<File> is a list of Files, it has a method "void add(File)" and a method "File get(int)".
List is just one class (interface actually but don't worry about that), but we can specify different type arguments which means the methods use this abstract type rather than a fixed concrete type in their declarations.
Why?
You spend a little more effort describing your types (List<String> instead of just List), and as a benefit, you, and anyone else who reads your code, and the compiler (which also reads your code) know more accurately the types of things. Because more detail is known, the compiler is able to tell you when you screw up (as opposed to finding out at runtime). And people understand your code better.
Once you get used to them, its a bit like the difference between black and white TV, and colour TV. When you see code that doesn't specify the type parameters, you just get the feeling that you are missing out on something. When I see an API with List as a return type or argument type, I think "List of what?". When I see List<String>, I know much more about that parameter or return type.
Bruce

What is the use of creating proxy services using WSDL.

Hi
Am a beginner in ALSB and i have a basic question. Business services are created using WSDL,thats sounds logical as we need to invoke the actual backend services .
Proxy services are connected to business services and what is the need that it can be e created using WSDL.
What is the use of creating proxy services using WSDL.

Hi,
I beleive you are confused because of the apparent inclusion of transport information in WSDL (that is the host:port/endpoint where the service is hosted). However, if you refer to the w3c specification of WSDL1.0 ([url http://www.w3.org/TR/wsdl]www.w3.org/TR/wsdl), you will find that WSDL has three separate sections:
1. The schema information that describes data element(s): specified in types
2. The message information ie message and port sections that specify the parameters and the operations
3. The service section that specify the actual protocol and endpoint binding.
Ideally, a WSDL can be broken down into these three separate components. Any WSDL containing the first two is called an abstract WSDL and is used for a top-down approcah for web services, and if the third part is used, then you get a concrete WSDL, containing invocation end-point also.
Comming back to your question one can typically use an Abstract WSDL for creating proxy service. This way, the service requester and integration can go on two separate threads where the common denominator or agreement between these two parties in terms of operation name and data element are imposed using the WSDL.
Thanks and Regards
Vivek Nandey
BEA Certified Developer for Integration Solutions

What is the advantage of abstract class and method???

hi,
* Why a class is declared as abstract???
* What is the use of declaring a class as abstract???
* At what situation abstract class will be used???Thanks
JavaImran

To save you from the wrath of the Java experts on this forum, allow me as a relatively new Java user to advise you: do NOT post homework problems here; you're just going to get told to go google the answer. Which would be a good move on your part. Especially since I found the answer to your questions by googling them myself.

What is the use of constructors

what is the use of constructors in abstract class when we cannot instantiate the class

Double posted and answered.
http://forum.java.sun.com/thread.jspa?threadID=740376

What is the use of this form?

Hi all,
What is the use of this form in include RV61B901?
How does this code send any information to the program calling it? Is Sy-subrc global so that main program will know the reuslts?
Code:
FORM KOBED_901.
DATA : l_anzpk LIKE likp-anzpk.
SELECT SINGLE anzpk FROM likp
                      INTO l_anzpk
                      WHERE vbeln = komkbv2-vbeln.
IF l_anzpk NE 0.
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ENDIF.
sy-subrc = 0.
ENDFORM.
Thanks,
Charles.

Hello,
This form sets the value of sy-subrc(which is global) based
on the value of l_anzpk.
Regards
Greg Kern

What is the use of additon in up to 1 rows in SELECT statement

Hi All,
         What is the use of up to 1 rows in select statement.
for example
SELECT kostl
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      INTO y_lv_kostl UP TO 1 ROWS
      WHERE pernr EQ pernr
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I'm unable to get in wat situations we hav to add up to 1 rows
please help me out...
Thanks,
santosh.

Hi,
Use "select up to 1 rows" only if you are sure that all the records returned will have the same value for the field(s) you are interested in. If not, you will be reading only the first record which matches the criteria, but may be the second or the third record has the value you are looking for.
The System test result showed that the variant Single * takes less time than Up to 1 rows as there is an additional level for COUNT STOP KEY for SELECT ENDSELECT UP TO 1 ROWS.
The 'SELECT .... UP TO 1 ROWS' statement is subtly different. The database selects all of the relevant records that are defined by the WHERE clause, applies any aggregate, ordering or grouping functions to them and then returns the first record of the result set.
Regards,
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What is the use of Alternative Calculation Type =2 and 4

Dear Friends
In pricing procedure in gross value, Net value for Item and Net value has Alternative calucation type is 2.
What is the use of it?
Without using it these value line are also fetching net value then what is the work of it. Please give me detail information with its effects in pricing condition tab page in sales document.
Thanking You
Arun

Arun biswal,
Correct Biswal. We have at varoius stages within Pricing procedure the "net value" which is calculated. Not only the alternative calculation type "2" is used if you notice carefully they are stored as subtotals at various levels.
For Ex Gross Value --> Subtotal =1 --> Calc type = 2
similarly for Net value for Item --> Subtotal =2 --> Calc type = 2
Net value 2 --> Subtotal =3 --> Calc type = 2
See, these are used to calculate the net value at various levels in pricing. The calculation Type has got a set of routines that will facilitate us in pricing. SAP has provided certain clauclated formulas or routines to facilitate us during calculation within pricing . Here the "2" is used for calculation without tax and store it as subtotal and display it or use it for further calculations.
We can use this "netvalue" amount for further calculations. It is used for clarity purpose when you issue a statement to customer. (like Confirmation order) at various levels like discount amt involved, Freight involved, Rebate amount invloved.....
Even without this Calc type or using sub total u can proceed....
Finally we have TOTAL --> Subtotal =A --> Calc type = 4
In the above line we have Calc type as 4, which means when you use TAX this calc type is used .
Routines are used to facilitate your process....
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Sathya

What is the use of Serializable Interface in java?

Hello friends,
I have one dout and i want to share with u guys:
Why Serializable interface made and actully
what's the use of it?
At which place it become useful ?
It is not contain any method then why it is made?
If anyone have any idea about this then please reply.
Thanks in advace
Regards,
Jitendra Parekh

t is not contain any method then why it is made?To point out to the user of a class (and the programs) that the design of this class is conforming to certain restraints needed for Serialization.

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Hi Friends,
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Message was edited by: Pradeep choudhari

Hi Maik,
Unit dimension will not be created automatically until and unless you have keyfigure referning units..
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What is the use of Withholding tax identification number field?

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I posted this question earlier but had to close because of no replies from anybody. Posting it again to see if I am lucky to get some answer this time.
Can someone tell what is the use of field Withholding Tax Identification Number? Does it help with the reporting? Where does it get populated on the report if given at vendor or master record or within the withholding tax customization for company code? What is the difference between creating it in the customization for withholding tax information for company code and vendor/customer master record?
As per SAP: Withholding tax identification number
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This number must be specified in Customizing either:
(a) As part of the withholding tax information defined for the company code, or
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Hi Pete,
The only thing that I could check is the content used in US:
See content of this field for US:
LFA1-STCD1 Social security number
LFA1-STCD2 Employer identification number
LFBW-WT_WTSTCD Withholding tax identification number for WT Type
In order to populate it, please kindly check the following:
The reason why you cannot fill in the field WT_WTSTCD in transaction
Fk02 however you can do it in XK02 (Change vendor centrally) can be due
to wrong customizing of the field status group.
Kindly check the following:
SPRO->
Finantial accounting -> Accounts receivable and accounts payable ->
Define screen layout per activity (vendors) -> Change Vendor(Accounting)
Company code data -> W/holding tax data, w/h tax 2 ->
FIELD Withholding tax code,w/h tax 2 will be probably just available to
display. Please, change it to optional entry.
I hope I could be of assistance.
Kind Regards,
Fernando Evangelista

What is the use of HTTPS 8181 port

Hi,
I am wondering what is the use of the port 8181 on the EE5 application server.
the second question. Why the application server open so many port on the same local machine. I agree that for security raison it is a good idea. But does application serveur use tcp connection to communicate between the server thread ?
So it is possible to add a thread in the serveur application to process some internal work. And of course it is possible to include this new thread in the communication process of the server ?
Can we have the map of all the tcp trhead use by the server application.
Regards
Herve Terrolle.

Your app has to run as root to listen on ports up to 1024,
also, some other app (apache?) may already be listening on port 443.
AFAICT port 8181 is just arbitrarily chosen, it might as well have been port 4430, or any other free port above 1024.

What is the use of commit work and rollback work

hao friends,
what is the use of commitwork and rollback work where we can use these open sql statements .
thanks,
anji

hi all
i have written the following code in my development system to change the records of my database.
SELECT * FROM zyikostl INTO TABLE itab.
LOOP AT itab INTO wtab.
    tabix = sy-tabix.
    DO.
      READ TABLE itab INTO ktab WITH KEY kostl_alt = wtab-kostl_neu.
      IF sy-subrc = 0.
        wtab-kostl_neu = ktab-kostl_neu.
        MODIFY itab FROM wtab INDEX tabix.
        CONTINUE.
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        EXIT.
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ENDLOOP.
MODIFY zyikostl FROM TABLE itab.
In the development system i have only few records its working fine,but when it is been moved to test system there are 2500 records in the database so the report is taking much time(more than 5 hours )
i sthere any solution for this ....
thanks,
vaasu.

What is the use of 'ALTER DATABASE CLOSE'?

Hello Everybody,
SQL*Plus: Release 10.1.0.2.0 - Production on Ma Aug 15 21:28:30 2005
Copyright © 1982, 2004, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.1.0.2.0 - Production
With the Partitioning, OLAP and Data Mining options
SQL> conn / as sysdba
Connected.
SQL> startup force
ORACLE instance started.
Total System Global Area 171966464 bytes
Fixed Size 787988 bytes
Variable Size 145750508 bytes
Database Buffers 25165824 bytes
Redo Buffers 262144 bytes
Database mounted.
Database opened.
SQL> select status from v$instance;
STATUS
OPEN
SQL> alter database close;
Database altered.
SQL> select status from v$instance;
STATUS
MOUNTED
SQL> alter database open;
alter database open
ERROR at line 1:
ORA-16196: database has been previously opened and closed
If i have to shutdown the instance and database then
WHAT IS THE USE OF 'ALTER DATABASE CLOSE' ?
I need explanation. Why should i shutdown?
Dont give me this answer.
ORA-16196: database has been previously opened and closed
Cause: The instance has already opened and closed the database, which is allowed only once in its lifetime.
Action: Shut down the instance.

If you read the documentation you will see that there is no ALTER DATABASE CLOSE command.
This is an undocumented Oracle command, which we are not supposed to use. Consequently we are not allowed to complain about the way that it works. Instead we're supposed to use SHUTDOWN IMMEDIATE.
Cheers, APC

What is the Use of Abstraction

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