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Static method Overriding- confusion

Atul Shukla
Ranch Hand

Joined: Oct 09, 2006
Posts: 34
Can anyone please help me in clearing my doubts on Static method overriding.

Confusion is :

class a{
static void v(){}
}
class b extends a{
static int v(){}
}

it gives compile time error? why .

I know the fact that we can redifine static methods in subclass but can't override ..and dynmic binding of methods will not work .. that's ok .. but why i can't redifine in the way i done above.. why java creators restricted that....

-Atul
Atul Shukla
Ranch Hand

Joined: Oct 09, 2006
Posts: 34
and please let me know other facts about static method overriding that will help in SCJP.

Thanks!!
yogesh sood
Ranch Hand

Joined: Aug 31, 2000
Posts: 108
Hi Atul,

Check link given below might be helpful for you.

http://www.coderanch.com/t/259844/java-programmer-SCJP/certification/Static-methods-redefined-not-overridden


If its green its biology if its stinkks its chemistry if it has numbers it is Maths and if it doesn't work its TECHNOLOGY
Mike Ngo
Ranch Hand

Joined: Oct 16, 2006
Posts: 89
overriding method must have same return type.
Illidan Yu
Greenhorn

Joined: Oct 21, 2006
Posts: 1
your static method in class b is neither overload or override method for the static method in class a.
so there will be a compile time error.
Mike Ngo
Ranch Hand

Joined: Oct 16, 2006
Posts: 89
Take the keyword "static" out and it will compile. The error is not about static method. It is because overriding method must have same return type.
d jones
Ranch Hand

Joined: Mar 13, 2006
Posts: 76
Could anone please explain in more detail why there is a compiler error.

I was surprised to see this since we are redefining the static method rather than overriding it.

Thanks
Burkhard Hassel
Ranch Hand

Joined: Aug 25, 2006
Posts: 1274
Hi ranchers,

I want add a little to your confusion

Once and again I read something like:
"static methods are not inherited" or
"static methods cannot be overidden, only redefined".

I won't say, these statements are not totally wrong, but quite misleading.
These statements only want to express that static methods don't show late binding.

But in a way, both statements are only half true, if not false.
I won't say much about the first, as it has not much to do with Atul Shukla's question.
But I would say, no, static methods ARE inherited, otherwise

would not print "Hi cowboys!".



To the second:
"static methods cannot be overidden, only redefined".
I also used to say "redefinition" when speaking about static methods, (as for example in the link provided by Yogesh). But now I reject the term "redefinition" for static methods. Why?

For example, if you try to compile
The compiler says:
foo() in B902 cannot override foo() in A901; overridden method is static final


The code would compile if you delete the final modifier. It would even compile (in Java 5) if you add the override annotation:

In my opinion, you could or even should say, that static methods CAN be overridden.

First, the compiler has the same opinion
Second, the rules for overriding non-static methods are the same as for static methods. I mean concerning e.g. return types, covariant returns, exceptions and accessibility modifiers. And as you all have to care about all of these, how you'd say, that static methods aren't overridden?
The fact, that static methods do not show late binding is not a reason to rename "override" with "redefine" for static methods.

I would use the term redefinition only for private methods, that are not visible in subclasses and thus can be redefined.

And if we assume, that static methods can be overidden,
the answer to Atul's question is easy and has been answered by the compiler already:

v() in a cannot override v() in b; attempting to use incompatible return type




Yours,
Bu.
Keith Lynn
Ranch Hand

Joined: Feb 07, 2005
Posts: 2367
I think the compiler error message is misleading.

It is clearly stated in the Java Language Specification that static methods are hidden, not overridden, in subclasses.

To get to the original question, this is from the Java Language Specification 8.4.8.3

8.4.8.3 Requirements in Overriding and Hiding

If a method declaration d1 with return type R1 overrides or hides the declaration of
another method d2 with return type R2, then d1 must be return-type substitutable
for d2, or a compile-time error occurs. Furthermore, if R1 is not a subtype of R2,
an unchecked warning must be issued (unless suppressed (�9.6.1.5)).
A method declaration must not have a throws clause that conflicts (�8.4.6)
with that of any method that it overrides or hides; otherwise, a compile-time error
occurs.
 
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