Why Not?
Yes, Even we can create an instance of interface and
abstract class also.
just see this below simple example
Main.java
-----------
interface Test
{
public void wish();
}
class Main
{
public static void main(String[] args)
{
Test t=new Test()
{
public void wish()
{
System.out.println("output: hello how r u");
}
};
t.wish();
}
}
cmd> javac Main.java
cmd> java Main
output: hello how r u
in above case Test is an interface but i created the object
for that interface.
hey uday u r master in java yaar, by people like u we can
change the java world keep it up dude. just keep on posting
these kind of impossible things ok. Thanks a lot for that :)
That it is not creating the instance of the interface. The
class which is there on the right side is called anonymas
call.
It is correct when the statement is as below
Test t =new Test(); he should give the ';' after the
paranthesis not after the '}'.
Please refer anonymas classes for other information how
they works...
Hi Anil, In this case uday sounds good!
As per your consideration if it is an anonymous class then
just remove that interface from our application and try to
compile it won't compile that code.
Here Test is an interface, for which to create the object
we need to provide the complete implementation for that
interface the same thing which uday did.
and again u check it if(t instanceof Test)
it is returning true that means t is an instance for Test.
and here the object is creating in the heap.
at finally here an instance is created for an interface.
Hi all,
I think Udaya is right and i have tested in the same and its
working. But if you think about the way JAVA has to make
instances(e.g. A a = new A()) will not work. It will give
you compilation error. So there is something we are not able
to see. Even I am trying to get what this example actually
working.
Feel free to update me if I am wrong...☺
Hi Uday.
Actually, in your problem, a reference of anonymous
inherently assigned to interface. In program, you no where
wrong, but instance of interface were not created, it
simply assigning the reference of anonymous class to
interface.. That is possible.
any way.. We can't create instance of interface.. In that
example only reference assignment to interface by anonymous
class.
Hope everybody can understand.
Hi Deepesh, uday is back again
Hey just see the question . can you create interface
instance?
just say the answer Yes or No?
my answer is Yes
how is it possible? Already i gave the example.I know that
this is anonymous inner class concept. But i don't want to
exceed this concept for too complex. that's why i did it in
this manner.Any How i thanks to all of you for more inputs.
but u can create the instance for interface. how can we
check an instance is,using instance of operator only. here
it proved hence the affrimative ans is right. i am not
plmbbing your knowledge it's just a kind of inquiry. Thanks
FYI huh!!!!
hi uday
I also tried this to call a interface of Collection and try
to instantiated but it is not working.
import java.util.*;
interface Test
{
public void wish();
}
class a implements Test
{
public void wish()
{
System.out.println("I am fine");
}
}
class Main
{
public static void main(String[] args)
{
Collection c =new Collection()
{
boolean isEmpty()
{
return true;
}
};
System.out.println(c.isEmpty());
Test t=new Test()
{
public void wish()
{
System.out.println("output:
hello how r u");
}
};
if(t instanceof Test)
{
System.out.println("t is a instance
of Test");
}
t.wish();
a oba=new a();
oba.wish();
}
}
But it is not working please explain.
No,Uday is wrong.
He has created an anonymous inner class Test with the same
name as interface Test.It doesn't depend on the interface Test.
If an instance for interface Test has to be created ,he
sholud have implement interface Test such as
class Main implements Test{
}
hi Uday,what you've done is, created an annonymous inner
class which is the implementer class of the interface.Here
the refernce variable is of the interface but it is
referencing to the newly created annonymous inner class
instance.
Here the instanceof operator returns true because
annonymous inner class is the implementer of interface and
instanceof always returns true with the same class or its
super class(try using instanceof with Object class, it will
always return true,may the object be of any class).
This expression instantiates a new object from an unnamed
(called anonymouns inner class)and previously undefined
class, which automatically implements the interface Test.
The class can explicitly implement one, and only one
interface, and cannot extend any class other than Object.
As it implement the Test interface so our anonymous inner
class has to implement the methods in this case we have to
implement wish() method.
In java we can not create instance of an interface, since
interface do not have contructor and as well as defalut
contructor.
No, you cannot create an instance of an interface. An
interface has no implementation - a class that implements
the interface specifies the implementation.
However, you can ofcourse have a reference variable of an
interface type that points to an instance of a class that
implements the interface. For example:
// List is an interface, ArrayList implements interface List
List data = new ArrayList();
It's good practice to program like this - program to an
interface, not an implementation. If you want to know more
about that design principle, see, for example:
[url=http://www.artima.com/lejava/articles/designprinciples.
html]Design Principles from Design Patterns[/url]
we can't create instance of an interface..
but we can create reference of interface, which can refer
to upcoming object of the class who implements that
interface..
@Uday Ur fooling amateur coders by creating an anonymous
class within the class . U cannot create an instance of an
Interface .If so try to make execute this code lol class
interface Test{
public void wish();
}
class Main
{
public static void main(String[] args)
{
Test t=new Test();
t.wish();
}
public void wish()
{
System.out.println("output: hello how r u");
}
}
Hi,
We can't create instance for an interface or abstract
class.Just remove the following code from the program
written by Uday.
interface Test
{
public void wish();
}
Remove the above code and run the program,then program will
compile and execute properly,because he used anonymous class.
along with your userid / name. ThanQ
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