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Date: Fri, 24 Dec 2010 00:13:06 +0800
Message-ID: <AANLkTikF+EbjnpyjGQRt7BKxF8ZE7MWPSbK_C=_Bhcbc@mail.gmail.com>
Subject: Re: strong type cast needed in java. (overriding enhancement.)
From: "Jimmy,Jing Lv" <firepure@gmail.com>
To: dev@harmony.apache.org
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Hi Hari,

      I see it may be possible to avoid the checking and implement the
strong type casting - however I am still wondering why shall we overcome the
difficulty, build a complex checking in compling to make it happen? Java is
not c/c++ and has its own style. So again what is the benefit we can see if
we have this feature?

2010/12/23 hari ks <hari_tcs@yahoo.com>

> c++:
>    base *b=new base;
>    sub *s=new sub;
>    s ->base::foo();  // private instance variable of base has 0 or unknown
> value while executing foo() method of base class..
>
> can't this be extended so as pass base class variable along with method
> call?
> may be something like
> s -> base{i=20,j=11}::foo();// here i and j were private variables of
> base..
>
> this concept could be implemented in java.
>
> thanks & rgds,
> Hari
>
>
>
>
> ________________________________
> From: hari ks <hari_tcs@yahoo.com>
> To: dev@harmony.apache.org
> Sent: Thu, December 23, 2010 6:06:46 PM
> Subject: Re: strong type cast needed in java. (overriding enhancement.)
>
> hi ,
>
> c++ allows more combinations between instructions(functions) and
> data(variables)
>
> than java.
> eg in c++:
> base* b;
> sub* s;  // sub extends base and both have method foo()..
> b -> foo(); // will call base foo()
> s -> foo(); // will call sub foo()
> s ->base::foo(); // will call base foo()
>
> java didn't add this mostly -because functions in super class might access
> 'private members' of super class  which there is no way populating in
> subclass
> object and throw Null Exception..
> Yet again - if these specific functions in superclass that could be
> accessed
> from subclass were compile time checked as not to access any private
> variable of
>
> super class, this feature may add meaning.
>
> There could be more better design than just preventing subclass not to
> access
> super class methods..
>
> thanks & rgds,
> Hari
>
>
>
> ________________________________
> From: "Jimmy,Jing Lv" <firepure@gmail.com>
> To: dev@harmony.apache.org
> Sent: Thu, December 23, 2010 3:34:51 PM
> Subject: Re: strong type cast needed in java. (overriding enhancement.)
>
> Hi Hari,
>
>      I see there is no such mechanism for Java now. I suppose it may be due
> to java single inheritance and dynamic bonding.
>     Technically strong type casting is possible with bytecode instruction
> or something, however I'd rather design it clear to avoid such invoking -
> say, if you want A.foo(), create A a = new A(), or avoid overriding foo()
> in
> B. It sounds a syntax problem to invoke a parent method in a child class
> instance while the method is already overrode.  It may have some problem
> with strong type casting. For an example, if you have a public basic type
> A,
> which has an implemented method foo(), and then create some internal
> implementation B, C, which C extends B and both of them override foo().
> With
> a factory of A you can get an object "a" which is really C instances, then
> it will be hard to tell what can be invoked for a.super.foo()?
>
>     Sorry I don't catch you that what is the benefit do you think for
> strong type casting on Java?
>
> 2010/12/23 hari ks <hari_tcs@yahoo.com>
>
> > I have put up a post here :
> >
> >
> http://programparadigm.blogspot.com/2010/12/method-overriding-enhancements-strong.html
> >
> >l
> >
> >
> > Suppose class B extends A.
> > A a = new B();
> > ((A)a).foo(); // still calls class B's foo() method.
> >
> > Can something like "a.super.foo();" method invocation be made possible.
> Or
> > ((A
> > strong)a).foo();  should call A's foo() method with B's instance data.
> >
> > similar thing for C++.
> >
> > Is there a way to already do this?
> >
> > thanks & regards,
> > Hari
> >
> >
> >
> >
>
>
>
>
> --
>
> Best Regards!
>
> Jimmy, Jing Lv
>
>
>
>


-- 

Best Regards!

Jimmy, Jing Lv

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