Use of abstract and interface?

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

Depends on what you want to do. An interface is more general (in that it doesn't define any actual behavior) and allows you to mimic multiple inheritance (a class can implement any number of interfaces whereas it can only extend one class (abstract or otherwise)). Abstract is good if you have a common base of functionality that all of the implementers will be using.
It's also fairly common to use both (i.e. the interface TableModel and the abstract class AbstractTableModel), so that someone who wants to completely write their own implementation is free to, while someone who wants to just extend or change the standard functionality could do that as well.

Similar Messages

Use of events and interface in class

Dear All,
Could you please explain why we use events and interface in class.
Also please tell me the use of TRY and ENDTRY.
Regards,
Amar

Events may be a way of communication b/w classes. Imagine you want to call certain code from one class, you would need for that public method, but you don't want to expose it to external user. So you may use events for that. Also events are used to notify that certain state of class has changed (tiggering event). Then all handlers of this event executes and react accordingly.
Interfaces are a way of provide a service to class which implements it. Imagine that you have class office and hotel and gas station . They don't seems to have something in common. However, there can be some external energy provider which will be an interface. Each class which want to have a lease with this energy provided can implement it (the implementation can differ in some way), so he can provided energy to different classes. This way you will achieve polimorphism (meaning you call one interface method, but code behind it differs from class to class).
Interfaces are also means of multiple inheritance. One class can implement several service (interfaces). In contrary it can oly inherit from one class.
Try endtry are just new way of handling exceptions .
Try to search a litte bit you will find lots of info on the above.
Regards
Marcin

Abstract Classes & Interface Classes

Dear members of the Sun Community
My studies are progressing and just 1 period ago we started doing Object-Orinted Programming in Java and I must say I'm quite fond of it. It's become quite clear that OOP is an important aspect of Programming and just can't be missed. We've learned about Inheritance, Polymorfism, Mutators, Inspectors, Uses-Relationships and everything else however now I've come to the point where I got a problem:
Up until now we have been using normal classes to work with in which you could create objects and in your main program create objects from that class however. We've just learned about Abstract and Interface classes. As far as I'm concerned I'm quite confused with both of them.
If I am not mistaken (please correct me if I'm wrong) Abstract classes are classes from which you cannot create an object but is only used to make a subclass inherit everything from this superclass.
I am not quite sure what Interface classes are as they just plain confuse me. Would anyone be so kind to maybe explain what all of this is ?
Thanks a whole bunch
Herazio

Funny enough that already solved the question !
Thank you so much for the quick reply ^^
Herazio

Receiver Determination and Interface Determination Condition conflict in ICO

Hi,
I found a strange issue today while configuring two receivers using the Receiver and Interface Determination conditions.
Sender - Proxy Service
Receiver1 - ReceiverA
Receiver2 - ReceiverB
Receiver Determination Condition : When Field1 = 100, message should flow to ReceiverA and ReceiverB
Interface Determination Condition (ReceiverA) : When Field1=100 and Field2=50 message should flow to a specific interface in ReceiverA
There is no Interface Determination condition for ReceiverB, for all messages having Field1=100, it should go to ReceiverB.
Test Scenarios:
1) Field1=100, Field2=50 : Message flows successfully to ReceiverA and ReceiverB
2) Field1=100, Field2=89 : Message fails to process from ECC itself throwing Interface Determination not found error. Ideally this is a positive scenario for ReceiverB and it should send the message to ReceiverB without any errors. But, this did not happen in this case
I tried the same by configuring the conditions completely in Receiver Determination itself without using the Interface Determination, it worked perfectly fine. But, just wanted to understand that if this is an expected behavior.

Hi Sherin,
As there are two receivers Receiver A and Receiver B.You need to create two bussiness components and two communcication channels for two receivers and one Reciver Determination, two Interface Determination,two Receiver Agreement.In Receiver Determination you need to keep the below and condition.
In the above screenshot the two receiver are Receiver B and Receiver C and Field 1 is Key_Value and Field2 is Emp_ID.
If the Key_Value=100 and Emp_ID =22 then the message should go to both the receivers B & C by keeping the following AND condition
If the Key_Value=100 and Emp_ID is not equal to 22 then the message should go only to Receiver B by keeping the following condition
You need not keep any condition in Interface Determination just create 2 Interface determination for two receivers.
Hope this helps you.
Thanks,
Durga.

Object oriented design problem concerning abstract classes and interfaces

I have an abstract class (class A) that takes care of database connections. It cannot be made into an interface as other classes extend it and all these other classes require the functionality in the methods it has (i.e. I cannot make all the methods abstract and then make this class an interface).
I have a class that contains data (Customer class) that I will create from the data I extract from the database. This class will also be created by the User and submitted to the database portion of the program. The Customer class has functionality in its methods which is required by the rest of the program (i.e. I cannot make all the methods abstract and then make this class an interface).
I have a factory class (CustomerFactory) that extends the Customer class. This has been created to restrict access to the creation and manipulation of Customers.
I have a class (DatabaseQuery) that extends class A. But now that I have retrieved all of the information that comprises a Customer from the database, I cannot construct a Customer without making reference to UserFactory. But UserFactory is a class that I don't want the database portion of the program to know about.
What I would like to do is have my DatabaseQuery class extend both Customer class and A class. But they are both classes and Java won't allow that.
I can't make either of the two classes that I want to make parents of DatabaseQuery into interfaces... so what can I do other than just keep a reference to UserFactory in my DatabaseQuery class?
Thanks,
Tim

>
What I would like to do is have my DatabaseQuery class
extend both Customer class and A class. But they are
both classes and Java won't allow that.
I can't make either of the two classes that I want to
make parents of DatabaseQuery into interfaces... so
what can I do other than just keep a reference to
UserFactory in my DatabaseQuery class?Just a guess...
The description sounds a little vague but it sounds like the correct solution would be to refactor everything. The first clue is when I see "database connection" as an "abstract class". The only hierarchy that a database connection might exist in is in a connection pool and even that is probably shaky. It should never be part of data records, which is what your description sounds like.
That probably isn't what you want to hear.
The other solution, which is why refactoring is better (and which also makes it apparent why the original design is wrong) is to create an entire other hierarchy that mirrors your current data hierarchy and wraps it. So you now have "Customer", you will now have "Customer" and "DBCustomer". And all the code that currently uses "Customer" will have to start using DBCustomer. Actually it is easier than that since you can simply make the new class be "Customer" and rename the old class to "DBCustomer". Naturally that means the new class will have to have all of the functionality of the old class. Fortunately you can use the old class to do that. (But I would guess that isn't going to be easy.)

Abstract classes and Interfaces

Why would you use these? Why not make a concrete class and extend them? I see why JAVA doesn't use mutiple inheritance but I don't see how allowing interfaces correctes that, after all what happens if two interfaces implemented by one class have two fully defined methods with the same signature but differant outputs?
I tryed googleing this but just got articles on when to use Abstract over interface and interface over abstract, which should have helped some but it didn't.
Can someone explain or post a link for a good example.

Why would you use these? Why not make a concrete
class and extend them? Check out the JDBC interfac (java.sql package).
The core Java API defines what types and methods it wants to use for DB interactions. But because every DB and driver is so different, there's no concrete implementation that the core API could provide for those types. It's up to the vendors to provide all the "how"--all the concrete implementations of the methods.
interfaces correctes that, after all what happens if
two interfaces implemented by one class have two
fully defined methods with the same signature but
differant outputs?That rarely happens (it has never happened to me in about 8 years of Java programming) and if it does, you just have to find a different approach--you can't meet both contracts.

Question about Classes, Abstract Classes and Interfaces.

I have been experimenting with Classes, Abstract Classes and Interfaces and wonder if anyone can explain this to me.
I was looking for a way to assign a value to a variable and then keep it fixed for the session and have devised this.
First I create an abstract class like this:
public abstract class DatabaseConnection {
private static String ServerName = null;
public static void setServerName(String serverName) {
          ServerName = serverName;
     public static String getServerName() {
          return ServerName;
}and then I created an interface
public interface DatabaseAccess {
     String servername = DatabaseConnection.getServerName();
}And finally the class itself with some test lines in it so I could see what was going on:
public class CreateDatabase extends DatabaseConnection implements DatabaseAccess {
     public static void main (String args[]){
          new CreateDatabase();
     public CreateDatabase(){
          setServerName("Server Name 1");
          System.out.println ("Before update ");
          System.out.println ("ServerName from Interface           = " + servername);
          System.out.println ("ServerName from Abstract Class = " + getServerName());
          System.out.println ("After update ");
          setServerName("Server Name 2");
          System.out.println ("ServerName from Interface           = " + servername);
          System.out.println ("ServerName from Abstract Class = " + getServerName());
          System.out.println ("==========================");
}The output I get from the above is:
Before update
ServerName from Interface           = Server Name 1
ServerName from Abstract Class = Server Name 1
After update
ServerName from Interface           = Server Name 1
ServerName from Abstract Class = Server Name 2
==========================I also tried this in another class which calls the above class to see if I get the same effect
public class CheckDatabaseAccess {
     public static void main (String args[]){
          new CreateDatabase();
          CreateDatabase.setServerName("Server 3");
          System.out.println("CreateDatabase "+CreateDatabase.servername);
          CreateDatabase.setServerName("Server 4");
          System.out.println("CreateDatabase "+CreateDatabase.servername);
          CreateDatabase.setServerName("Server 5");
          System.out.println("CreateDatabase "+CreateDatabase.servername);
}The output of which is this:
Before update
ServerName from Interface           = Server Name 1
ServerName from Abstract Class = Server Name 1
After update
ServerName from Interface           = Server Name 1
ServerName from Abstract Class = Server Name 2
==========================
CreateDatabase Server Name 1
CreateDatabase Server Name 1
CreateDatabase Server Name 1Can anyone explain why I appear to only be able to change or set the ServerName only the once?
Is this the correct way to do it? If it is it's exactly what I am looking for, a way to set the value of variable once in a session and then prevent it being changed.
Or is there a better way of doing this.
What I want to use this for is for example, storing the accesses to a database on a server. I won't know what server the database will be stored on nor what the database is called so I create an INI file which stores this information in encrypted format, which is set by the database administrator. It occurs to me I can use this method to then retrieve that data once and once only from the INI file and use that throughout the life of the session to access the database.
Any help appreciated
Regards
John

Not gonna read all of it, but this jumps out:
public abstract class DatabaseConnection {
private static String ServerName = null;
public interface DatabaseAccess {
     String servername = DatabaseConnection.getServerName();
}You have two completely separate variables (with two different names, for that matter, since you were inconsistent in your capitalization, but it wouldn't make a difference if they did have the same name with the same case). And the one in the interface is implicitly public, static, and final.
Anytime you refer to "servername" through a reference of type DatabaseAccess, it refers to the one declared in the interface.
Anytime you refer to "ServerName" inside the DatabaseConnection class, it refers to the one declared in that class.

What is the difference between Abstract class and Interface ?

Hi,
Could u plz tell me the difference between Abstract class and Interface?
Thanks in advance.
Gopi

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.

Difference between abstract classes and interfaces

I actually wonder about what are the differences between abstract classes and interfaces may somebody give an example code about it?
and i have one more question how can i use interfaces like multiple inheritance ? i mean when i implement an interface like
class a extends b implements c,di have to use all c and d methods but what that methods means?
I mean as i know we cannot make implementations of methods in interfaces
but for example in runnable interface there is a method like run() and it has been defined somewhere because it knows what to do(i mean when it will run), i just write my code into that method .

Once you get past the starting point (I am referring to the OP here), there are a few salient differences:
You can only extend (or generalize) a single superclass; however, you can implement (or realize) multiple interfaces. As such, all things being equal, using an interface in lieu of an abstract class 'frees' your design. Later, if you want the implementor of an interface to inherit from another class, there is not issue.
Any abstract method specifies a contract. However, abstract classes allow you to also add common behavior to subclasses. This is an overused justification for abstract classes, IMO. You can achieve the same effect using delegation and still having interfaces.
Always program to interfaces wherever possible. This means that you define an interface and have an implementing class (usually at a minimum). Do not do this for all your classes, but rather the ones that make your system unique (the domain model or M in MVC architecture). This allows you to later change implementation with a minimal amount of refactoring. This is a core precept from the Group of Four and any number of decent programming books.Best of luck.
- Saish

Data transfer b/w SAP to Java using IDOC and Interface SAP Jco

Dear Experts,
The challenging requirement we are having is, we need to create the interface for data transfer between SAP system and the Java system. The data will be transferred from SAP to java and similarly once some processing done in Java again the details needs to be transferred from Java to SAP.
For this data transferred we are planning to use IDOC process and for interface "SAP Java connector (Version 3.0.5)" we are planning to use. As per our understanding, from Java side one program needs to be written to connect with SAP as "Registered program". This registered program will appear in SAP GATEWAY automatically and using tRFC, TCP/IP connection both SAP and Java system will be connected.
In this case we are having some doubts.
1. The data from SAP is going to be transfered from one Custom transaction (Z tcode). Once "Outbound IDOC" will get triggered and will carry the details. Now the doubt is, whether the data / details will get transfered to JAVA system automatically or we need to perform any other steps from SAP ABAP coding...(like converting in to flat file, XML file and etc) ??
2. We are planning to install "SAP Jco" in Java server. Is this correct...??
3. Other than SAP Jco any other softwares needs to be installed or not..??
4. Since we are going to trigger the "outbound IDOC" from custom transaction, we are planning to develope one program in SE37. Other than this any other program we need to develop or not..??
5. Any sample Java program for the SAP Jco version 3.0.5 to create the "Registered program" with SAP..? (e.g. SAP Listener program).?
If anybody has detailed steps or explanation please share it with us.
Thanks in advance
Warm Regards,
VEL

Hi All,
For the above mentioned issue, we implemented JCo software in JAVA system and created the JAVA program including SAP logon credential details like Client, User name, password and Language details.
When this JAVA program was compiled successfully then, that non SAP system will appear in SAP gateway Tcode.
Once non SAP system started appearing in SAP gateway that means, both SAP & Non SAP are connected automatically.
Regards,
Velmurugan P

Use of abstract interface

I have a series of questions....... Go through.
What is the use of abstract interface in java ?
What is the use of static object in java ?
What is the use of abstract key word to variables ?
Object reference passed to method are final. Can ' t we change it ?

class Testing {
     int i;
public class RefFinal {
   public static void f ( Testing t1, Testing t2) {
       Testing temp;
       temp=t1;
       t1=t2;
       t2=temp;
       System.out.println("value of i in t1 =" +t1.i);
       System.out.println("value of i in t2 =" +t2.i);
   public static void main( String args[]) {
      Testing t1 = new Testing();
      Testing t2 = new Testing();
      t1.i=10;
      t2.i=20;
      f(t1,t2);
      System.out.println("value of i in t1 =" +t1.i);
      System.out.println("value of i in t2 =" +t2.i);
}      Here the code explain why?

How to find out what are the interfaces used for Job and Job Codes

HI All,
I just wanted to know how do we find out what are the interfaces used for Job and Job codes .
Thanks In Advance
Sunny

Hi,
Here is an idea for your request.
Basically you can create a simple query on multiprovider 0TCT_MC01.
Filter: you can use a variable for restriction of time ( calday, or calmonth) since you should be interested for a time period.
Choose following characters into your objects:
InfoProvider ( 0TCTIFPROV ) - you can create a variable for choosing infoprovider before query runs.
*Tp.[Type of BI Application Object] 0TCTBISOTYP = filter this with 'QUERY' or whatever your need is.
*BI Application Object 0TCTBISBOBJ, ( this will give you the name of the queries)
In key figures choose, Count for BI Appl. (0TCTWTCOUNT).
(number for query run)
Create a condition , for top 20.
Hope this helps.
Derya

Abstract class and interface having same method

Hello,
Here is my problem. Suppose we have one abstarct class and one interface.Here is code-
//Abstarct class
abstract class X{
abstract void myMethod();
//Interface
public interface Y{
abstract void myMethod(){}
Now i have a class which extends both abstarct class X and interface Y.
If i call myMethod() from this class. Whose myMethod would be called.Will it be of abstract class or interface?
Many Thanks

Hello,
Here is my problem. Suppose we have one abstarct class
and one interface.Here is code-
//Abstarct class
abstract class X{
abstract void myMethod();
}OK, so far...
//Interface
public interface Y{
abstract void myMethod(){}
}An interface cannot have code (the {} part), so this won't work.
Lets pretend though, it read
//Interface
public interface Y{
abstract void myMethod();
However, the abstract class above can have code;
If you extended X and implemented Y (with no code in it), you would have to have a myMethod() implementation in your code. That's the one that would run.
Now, let's pretend the abstract class above did have code in it.
//Abstract class
abstract class X {
abstract void myMethod() { System.out.println("Hello"); }
Then, you wouldn't have to have a myMethod() implementation in your class which extends X and implements Y (it's defined in X). If you didn't have one, the method in X would run. If you defined your own myMethod() implementation in your class (which extends X and implements Y), then your own implementation would run.

To create interface using Integration Repostiory and Integration Directory

How To create interface using Integration Repostiory and Integration Directory for Java appln???

Hi,
Are u talking about Java based applications. If so, one of the way is to go with Java Proxies.
Go thru these for more:https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/a068cf2f-0401-0010-2aa9-f5ae4b2096f9
https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/f272165e-0401-0010-b4a1-e7eb8903501d
https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/d06315a6-e66e-2910-039c-ba8bbbd23702
Rgds,Moorthy

No list tree of device and interface, software in MAX sytem. using pci 6034E and chasis 2345

Hye, i got the problem about this device.
I using PCI 6034 E which will connect to SCC 2345 to measure current and voltage.
My os is 32 bit Windows XP.
First i install this software, my MAX listed the tree of devices & interface which is PCI 6034 E and chasis 2345, and all download software are listed in tree of software.
By the way, when i start to measure the current, my MAX is working fine.. but, the problem is starting in the next day, wheni try to measure againt, all the list are dissapear. Then i uninstall all the NI component and reinstall again. Thereare a lot of install and reinstall again and again.. By the way the result is still same. Do not have any tree appear..
so, any colution for my problem?
i try to solve this problem, and i read that when the tree of devices and interfaces not appear, it's maybe because we using driver : NI 488.2 , i try to uninstall this driver.. by the way the result is still same...

sahizansalman,
It looks like the same is happening with the Software list. This is often a sign of a MAX database corruption. I'd try the steps outlined in this knowledgebase:
What is the Process For Removing MAX Database Corruption?
Feel free to post back if this does not work.
By the way, do you know what device is showing up as unknown in the device manager? You did not mention anything besides your PCI DAQ card and SCC 2345, which are showing up fine.
Message Edited by mishkin on 03-11-2010 07:42 AM
Misha

Use of abstract and interface?

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