Difference Between Interface and Abstract Class

5. An interface can extend another Java interface only [...]

It sounds like what you’re saying is that an interface can
ONLY extend ONE other interface?

thanks for the abstract and interface difference ..
please send this complete book for me

if interface object’s initialization with corresponding class instantiation examples would have presented.

Instead of picking points from Java books about the differences, it would be better if you describe the main advantages of using interfaces and abstract class, when to use interface and abstract classes. That would add value to your question and make easy understand to the viewer.

Excellent tutorial on abstract and interface difference
One more point – If I dont want multiple inheritence then which one is better to use?? Interface or abstract class??

The difference no 8.
“In comparison with java abstract classes, java interfaces are slow as it requires extra indirection.”

What is this “extra indirection”. I have seen same difference point in other sites without clear information.

Also how can we prove that java interfaces are slow than abstract classes.

to know more about the difference between interface and abstract class ….read SCJP kathy sierra’s book….best as far as i know…

good i learn very much from this webiste

thanks for giving explanation and difference between these two and i need more details about core java

Hi,
some nice tips on this site!
I also don’t get difference 8 though – can you clarify please?

how to utilize interface in another class without implementing that interface

It’s good, lists the complete abstract and interface difference in simple way

Hey Raghu,you can do that by making the implementing class abstract and then extend it in another class of your choice .

apart from difference between them,
use Interfaces when you require 100% abstraction otherwise use abstract class

Why interface cannot be instantiated?

why a default constructor is provided by jre in java

thanx for the complete abstract and interface difference thing… its good, it helps me alot

Your website looks so good..

Hi,

We can also discuss like an interface will be used for an object reference of its implementing class while abstract class object reference can be used for its extending class.

your explanation is very good
please send me the whole book

interface is the most powerfull solution of using multiple inheritance because java does not support multiple inheritance

Thank you

good explanation but
explain new topics on java

Thank you…very much……..
please…..
send me one copy of this book.

ya i accepted this concepts and more useful for beginers……..

Hi.
can u give me the difference between the two following statements

1.A sub1=new B();
2.B sub2=new B();

where A is suerclass
B is the sub class

//method over riding
class A
{
int i,j;
A(int a,int b)
{
i=a;
j=b;
}
void show()
{
System.out.println(“super”);
System.out.println(i);
System.out.println(j);
}
}

class B extends A
{
int k;
B(int a,int b ,int c)
{
super(a,b);

k=c;
}
void show()
{

System.out.println(“sub”);
System.out.println(i);
System.out.println(j);
System.out.println(k);
}
}
class Override{
public static void main(String args[])
{
A sub1=new B(1,2,3);
B sub2=new B(1,2,3);
sub1.show();
sub2.show();

}
}

first you have to concentrate on Polymorphism concept , why because if you are crating the object and the object reference is give to super class , then on that time it checks whether that method is there in subclass or not at compile time

plz write a default construcctor in side class A then above code compile and run successfully………..

example is nothing but a polymorphism………

thanks it is very useful.

thanks for clarrification

When to use abstract class over Interface ?

Thanks in Advance
Remya

its a great help for understanding main difference between both abstract class as well as interface.
to know more about the difference between interface and abstract class ….

plz mail me the difference in abstract and final keywords in java

what is difference between overloading and overriding?

Wow… it is too good Blog..

it is too Elegant..,
Conceputally Nice…,

I like the Way u explain about “Difference between Abstract class and Interface”

What my suggeation is…, Write one Example Program For Every Explanation..

thanks for ur explanation

is it possible
abstract class A extend b implements c
{
}

thanks for explain it

thanks for the basic help in java

How many maximum number of Interfaces are implements in our class?

Hi….. It is too good.

Hi Joe,
This is very useful.Being a fresher its very useful for me. Mainly the website design is really fantastic.Keep going……….

why abstract class does not support for the multiple inheritance?

Please mail me this book.

Thanking U for providing a comprehensive information. may allmight with u to have ur destiny.

hai
very nice and good.

Thanks it was a little helpful for me….

Difference B/W overRiding and overLoading:

in over riding perameters and type of method remain same. but its internal properties changed you can say over ridden.

in over loading the name of method is same but parameters are different. according to type or in number. the call to these functions depends on the parameters compatibility…

dis infermation is very well and easy to understanding…..i am feel good………

the main difference is interface doesnot talks about implementation.it talks about requirement specification
abstract class:
it talks about implementation but not completely(partial implementation).

Hi readers,
i go through all above mentioned discussion regarding interfaces and abstract classes. So i feel some person need example where to use interfaces . In order to understand the interface concept just thinking that how jdbc api worked with each and every dbms(oracle,mysql etc) because jdbc api provide just interfaces and implementations of these interfaces are provided by the dbms vendor that implementations are known as database drivers. (9888327755-ssubhi_2003@yahoo.com). Feel free to discuss any java topic

thanks

dis infermation is very well and easy to understanding…..i am feel good………

well written

Easy and point wise description help me to understand the exact difference.

Im ery helpful to all, this discussion has provide me clear knowledge.
yes and i most lke info provided by satnam singh, you know we were using that but never came in mind that how basic java get used over there. great….

nice artiacle and very helpful also…Can anybody explain why java interfaces are slow and how it requires extra indirection??

Thanks in advance.

All the above mentioned pts. are totally easy to undertand.

hii can any one help me to know how interface is slower than abstract abstract class.
in the above article what indirection means?

Really nice points to understand thanx

Could you please give some program examples, about their diffrences

hi i through all above ur’s feedback pls can u people send me what is difference between class interface and abstract class
send me j-krishna@live.com

how multiple interface is used instead of multiple inheritance??

before studying this information i am not clear about interface and abstract class.just now i am know about this topic.thank you

Neat & Clear!!! Information provided can be understood by even a average student.

i need a difference between a class and a interface?

Very well written article

All of the variables in an interface are implicitly static and final.

hai guys, how to use in spring with struts?

nice info

thanxxxxxxxxxxxxxxxx

all i saw was jibber man.. please for heavens sake , use examples…!

nice explanation

nice explanation

Mr. Satnam Singh explained very well…..so nice

thats good, i understand the difference between interface and abstract class.
but can you give a code which show the difference ……

Easy to understand

its very helpful to me thanqs for your kindly info…….

its very help to me .thanqs fro your kindly info…

nice difference between interface and abstract class

i have a doubt, if we implement an interface need to write all the methods in that interface even if we don’t need the methods .what is the case of abstract class?

thanxxx

plz send me the complete tutorials so that it will helps me a lot

Thank you so much for giving the best Answer…

because of i am so confused
Thank you again.

abstract class and java class both are same or different???

HI Joseph,

Let me know that why we are choosing “Interface” & “Abstract class” for a good application..

Thanks in advance,
Selva

hiiiiiiiiiii joseph,

what is we commoly use in java project that is absruct class or interface?

my second question is that what the actuall meaning of implimentation and extand?

my first ques is 1)6 points of difference between object and class.
2)6 points of difference between dynamic binding and message passing.

ques) explain briefly why cant we use a keyword as a variable name???

tell me true or false…
1. when if statement are nested,the last else gets associated with the nearest if without an else.
2. one if can have more than one else clause.
3. a switch statement can always be replaced by a series of if…else statements.
4. a switch expression can be of any type.
5. a program stops its execution when a break statement is encountered.

very very good explanation on the differences

This is quiet good….
It may be useful for interview…

very accurate answers.good.

very nice answers good

This is really good….
It is useful for interview

Its so easy to learn even if the people doesn’t know java

tt

This is really helpful!!

Hi Joe,

Can you please tell me when to use Abstract class and when to use Interface in an application?

give reallife example of interface…….

hey i didnt get my answers,,,,,,,,,,,,

thank u sir

plz mail me similarities between an interface and classes

In interfaces we cannot have any implementation for methods but that’s not the case with abstract classes we can have implementation for methods.

thank you for giving informations
but i want more details …..

nice explanation for interface and abstract class

about java buzz words ?

It is very use full for me….. Thank you… by V.Vinoth from poondi

Thank you very much … it was very useful to me

thank u for giving this wondarful information

Hi Joseph sir,

Thanks for the detailed explanation of diff between abs class and interface. I would like to know , on what basis programmer deside he need to use interface or abstract class ? and if interface is having 2 abstract methods(only) and abstract class is having 2 abstract methods(only) then what was the difference in both ? Please post answers for the questions.
Thanks and Regards,
Praveen G

Very helpful…

plz give me the 6 points of difference between messege passing and message binding……..

i still have a doubt, when we have to use interface and when we have to use abstract(class as well as method)

plz suggest me how can i become expert in making programs by myself?? because coding postion in java is a biiiiigggg giant for me can u suggest how can it be easier for me the coding in java

nice web site

its really helpfull for my class lacture

what is the main reason to create abstract class?…..
sir i know we cant create object of abstract class and we also provide method body in abstract class compare to interface…

good and simple

difference b/w instance variable and class variable.

what are the changes to a variable ,method and a class when a final keyword is added to them.

I was put forth this question in the interview.Please help.

When you have to pass the data in the form of keys which collection would you use ?

thank you for information about abstact class and interface

Apart from these differences one more difference is in my mind, i want to ask is it correct or not-

* interface can be declare as a member of a class while abstract class is’t.

some interface define just constants and no methods……thanks 4 giving such simple and good differences….can u send me whole book on my given id….plz…..

can u send me the real time example that when do we use interfaces and when do we use abstract class

Its very easy and useful to me

One more point:

1. If we created Interface we can add new methods easily, but abstract is not easily.
2. Interface act as Service layer its interact different types of two entities(node) but abstract is not.
3. Interface is high level of abstraction(fully abstract class) but abstract is next level of abstraction.

I have added some point. Please verify and let me know if it is correct or not?
Please forgive any typical and grammatical mistake.

Please send me if any feedback: murugadoit@gmail.com

Take all :)

Abstract class start with letter “A” and Interface starts with letter “I”.

What is the purpose of using Abstract class????

Hi,please provide the Real-time examples for Interface and the Abstract class.So that every one can understand easily..

Hi Joe ,
when we have to use abstract class & interfaces can you explain

If i create any reference variable to an interface and also i create the object of implementing the class.just mail me the difference

Hi Joe,

First of all its a nice blog. Congrats for writing and maintaining this blog.

On Dec 19th you have mentioned that “an interface can extend multiple interfaces”.
But java doesnt support multiple inhertance. Please explain your statement.

With Regards
Shiv

thanks joe for detailed explanation

good explanation

Hi All,

I am new to java. Can you please explain what are the topics covered in J2EE? if i want to serve in Java field, what are all i need to learn..

Please help me.
-Thanks in advance

Hi All,

I am new to java. Can you please explain what are the topics covered in J2EE? if i want to serve in Java field, what are all i need to learn. and also please explain the ways

Please help me.
-Thanks in advance

what if abstract class implements two interfaces then it has to provide bodies for method declarations in interfaces or not?

when we have to use abstract class & when we have to use interfaces can you explain

Thank you,that the difference between them is clearly understood to me.Please explain in simple programatic way?

when we have to use abstract class & when we have to use interfaces can you explain?

Thank you for clearing doubts…..please send this book to my mail id…i have some more doubts

This differences can be found everywhere, say new things like
1. when to use Interface and when to use Abstract class
2. which one is efficient ?

Just give some practical programming scenarios.

hello nyc blog

hiiii gud source of info……keep goin!!

hello

catch
{quotient=divide(num1,num2);
cout<<"The quotient is "<<quotient<<endl;
}
try(char *exceptionString)
{
cout<<exceptionString:
}
wat is the error in this code……..

Thank you sir it is really helpfull to me keep going on………..

Thanks a lot !!!!!!!!!!!!
you are The Best.
Thanks for writing and maintaining this nice blog. this is very nice blog.

pranav thipse.

Hi Sir, really good blog.Very much impressed by the blog and the information displayed.It would be nice if you can start covering advanced topics also in this blog.

Hi joe,
I know about Interfaces & Abstract classes. But can you please let me know why there are 2 different things Interface & Abstract class. When only Interface was enough(I guess, to do all the work.)

i stil hav a lot of doubts.can u jst giv some example and also show whn to use wht?

it was really nice and in a very simple language… thanks joe

can any1 give me A simple program for managing abstract and interface which includes all aspects as joe said?

can any body explain me constructor in detail…i don’t no the use of it pls. explain me..

Thanks joe really helpful,But I’m having confusion about the term “extra indirection” used in 8th difference can u please explain what it is ?

I have a doubt Joe,

In my current coding, my aim is to call the same method in different classes simultaneously. say class1 and class2 access add()method present in class3. My issue is a null pointer is getting displayed on execution. Can u guide me on this???

can you please explain how the servlet communication done to other? explain different ways ?

Thanks you for giving to this this answer.

Some simple examples would be really great :)

this is awesome. thanx

Please any one explain ,where we use Abstract calss and where we use interface .
Plese give example

is an interface implicitly an abstract class?

Thanks…

Good one. I had a look at the following website. that too looks good.

https://www.logicsmeet.com/forum/23488-Difference-Between-Abstract-Class-and-Interface-in-.NET.aspx

any book to get a good knowledge of java in simple and easy text?

hi thanks for differences of abstract and interface .please send the complet book to my mail id are the address in url pattern (rakesh.gandua9@gmail.com)

hiii,,,,thanku for u r description plzzz send the java book which can be helpful in the basics point of view to my email id (kalyaniapple93@gmail.com)

In the 7th difference pls give an example that how can we invoke abstract class if main exist…

pls send the best book for core java to my mail id i.e. anjaniatmakuri@yahoo.com

Nice work again…but i don’t understand 7th difference,can u explain me in detail.

Is it possible to implement Iterator interface
Methods in our own class?
for example

/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package Collection;

/**
*
* @author arjun gm
*/
public interface java.util.Iterator {
public abstract boolean hasNext();
public abstract E next();
public abstract void remove();
}
public class MyInno implements Iterator {
boolean hasNext()
{
System.out.println(“Add”);
return true;
}
void remove()
{
System.out.println(“Sub”);
}
public static void main (String args[])
{
MyInno my=new MyInno();
my.remove();
}
}

why variables declared in interface are final by default and why all members are public by default?

when and where interfaces and abstract class is to be use?

Thanx…..

nice explanation .Can u tell me how can we instantiate Abstract class

No, you cannot instantiate an abstract class. An abstract class is a class that is not yet “finished” – it contains methods without an implementation. A non-abstract subclass is supposed to implement those methods

You can create anonymous subclasses that implement all abstract methods:

AbstractAction action = new AbstractAction(“Hello”)
{
public void actionPerformed(ActionEvent e)
{
// this is the only abstract method in AbstractAction
}
};

These anonymous subclasses only support the constructors of the abstract class though, you can’t create your own ones. If you need that kind of behaviour you need to create actual subclasses

Joe, Can you please re-design the site to help the user to reply to a specific comment, rather than commenting in end.

It would help people in following better, to the question/tips left by fellow contributors

theoritically good .try to show it with examples….

Thanks a lot !!!!!!!!!!!!
is very useful for my exam preperation
Thanks again

Thank u very much…… this explanation is short pls put more anyway thanks guyz

such a nice example for prepare an interview

Hi all,
I came to know that most of you are clear with the differences. Can anyone of you explain this point,“In comparison with java abstract classes, java interfaces are slow as it requires extra indirection.” Even i read in several sites interfaces require extra indirection and hence slow. why is it and what is indirection,

nice one but give one example

when we use abstract class? and when we use interface? pls reply

Can you please explain with an example for both abstract and interface? It is very useful and easily understand

thanks man u are great!!

perfect….dude….

when do we use interface and abstract class ?? what is the necessity of using both of them differently if they are similar to each other ?

where should we use interface and Abstract?

are you alive

grt site.

thanks for yr dis ans………

Please let me know how the abstract class is faster than interface

Very helpful site. Will share it on facebook :)

Interface Requires more time to find the actual method in the corresponding classes.
this is why Abstract class implementation is faster than interface

abstract class does not have a body

sometimes a problem occurs where we have to only define methods in abstract class,but using only methods in a class is against an Object-oriented concept.that is the reason we use interfaces..because interface is not a class so we can easily put methods in an interface.

why we use interface or abstract class and what is the best approch interface or abstract class

This is really useful

Thanx a lot

plz send me some java course materilas, i am learning initial stage and i need not take any training, i have learn java my own thats why please send me some course meterial that materials useful my starting stage.

plz avoid authors books

Is it possible to implement Iterator interface
Methods in our own class?
for example

/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package Collection;

/**
*
* @author arjun gm
*/
public interface java.util.Iterator {
public abstract boolean hasNext();
public abstract E next();
public abstract void remove();
}
public class MyInno implements Iterator {
boolean hasNext()
{
System.out.println(“Add”);
return true;
}
void remove()
{
System.out.println(“Sub”);
}
public static void main (String args[])
{
MyInno my=new MyInno();
my.remove();
}
}

Thank u for useful information

Can we extends the interface ? if yes then show me by one example if no then tell me a proper reason ?

thanks

Thank you for giving the nice info….

its a useful tutorial

its a useful tutorial

thanks for giving valuble information…….. friends please send some more java material to me my e-mail is:govind.588@gmail.com

Thank you for providing us these answers

if any interface is enxtend the same abstact method with in the abstract class then what will happen……. how? please send me one example////

What is the significance of Interface?

Its just a declaration of method names. But the implementation is still in the class.

Any one can answer?

joe .plz explain
how transient keyword works with small example and what do u mean by serialization

hi joe
can i know exact usage of both interface and abstract class?

hai joe sir,
Iam a begginer in java,before reading this blog i had lot of confusions in my mind now I got clear idea about interface and abstraction.Thank you so much for that……can you plz include some examples(programm).

Biji A

Nice blog:)

hi Guys ……

My Question : Can Over riding supports Inner classes in java?

package com;
public class Test
{
public static void main( String[] args )
{
A b = new B();
System.out.println( “Calling b.test(): ” + b.test() );
B b1 = new B();
System.out.println( “Calling b.test(): ” + b1.test() );
}

private static class A
{
public static String test() { return “A”; }
}

private static class B extends A
{
public static String test() { return “B”; }
}
}

if you need any help in java … contact me …

siddardhas@yahoo.co.in

examples are good for me……*

nice blog..

thanks

not bad

pls include some examples

thank u…

Thanx for difference …
it is help me lot in tomorrow exam of java ….

thanks…It is very useful….

thanks a lot it is helpful for my exam

Could you Please Explain Difference Between Interface and abstract class with real time example?

i think 5 point i have doubt

malli,
“i think 5 point i have doubt”
coming to your Qestion

Class A extends Class B(abstract class)
{
// Class can extend only ONE Class
}

Class A implements Interface A, Interface B, Interface C {
//Where as Class can implement Multiple Interfaces
}

Hope you are clear now

hi, sir

i have recently complete my MCA and Join a company as java programmer, but i dont have knowledge of java, and i dont have much time to join coaching, so is there a way to learn java pls suggest me some sophisticated way to learn java programs…..

Good initiation

Very useful and very clear. Thanks.

1 more diff=
An interface cannot have a constructor whereas an abstract class can have a constructor which is called indirectly by the derived class.

Good

its good

its very useful for all.
thanks

hmmm have to improve

hmmm have to improve