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From: RedGrittyBrick on 10 Mar 2010 04:05
On 10/03/2010 08:50, Javas wrote:
> On Mar 10, 9:31 am, Lew<no...(a)lewscanon.com> wrote:
>> Please reply to the list.

Eric Raymond collected some notes on getting the best out of Usenet. I
found them useful, maybe you will too. References below.

>> Javas wrote:
>>> Guruji! Don't try to act smart. Just try to share your views and
>>> convey your requests in a cordial mannar. Hope you understand your
>>> mistakes. I'll correct me from my next post onwards. Anyways, Thanks
>>> for your answer.
>>
>> #1: If you're so smart, why are you asking us for help?
>
> I never advertised to you that I am smarter than
> you. I guess you are trying to get personal.

http://www.catb.org/~esr/faqs/smart-questions.html#not_losing


>
>> #2: What wasn't cordial about my manner?
>
> You could have just answered the questions and
> stopped there, instead of worrying about whether's it my homework or
> assignment work. Or atleast you could have suggested me to name the
> class properly. But you chose the wrong path.

http://www.catb.org/~esr/faqs/smart-questions.html#homework


>
>> #3: What mistakes? Trying to help you, apparently.
>
> You had some other intentions too other than
> helping one alone.
>
> Above all, I just wanted to convey it to you.
> That's the reason why I sent it to you alone.

http://www.catb.org/~esr/faqs/smart-questions.html#noprivate

--
RGB
From: Joshua Cranmer on 10 Mar 2010 07:37
On 03/10/2010 12:53 AM, Javas wrote:
> Why does the above code results in a compilation error? since it is
> always invoking class B's process() method which doesnt throw any
> exception.

How can the compiler know that you're only invoking B's method?

--
Beware of bugs in the above code; I have only proved it correct, not
tried it. -- Donald E. Knuth
From: Lew on 10 Mar 2010 07:56
Javas wrote:
>>> Guruji! Don't try to act smart. Just try to share your views and
>>> convey your requests in a cordial mannar. Hope you understand your
>>> mistakes. I'll correct me from my next post onwards. Anyways, Thanks
>>> for your answer.

Lew wrote:
>> #1: If you're so smart, why are you asking us for help?

Javas wrote:
> I never advertised to you that I am smarter than you.

Nor did I.

> I guess you are trying to get personal.

And you weren't?

Lew wrote:
>> #2: What wasn't cordial about my manner?

Javas wrote:
> You could have just answered the questions and
> stopped there, instead of worrying about whether's it my homework or
> assignment work. Or atleast you could have suggested me to name the
> class properly. But you chose the wrong path.

You did name the class properly, afaict, and what is wrong about my "path"?
Who said I was "worried"? This is a discussion group, not your little unpaid
help-slave labor pool; I was discussing. Helpfully, too, though you missed that.

Lew:
>> #3: What mistakes? Trying to help you, apparently.

Javas wrote:
> You had some other intentions too other than
> helping one alone.

Oh? You misread my mind there, Kreskin. Everything I said in my first
response was to help you.

> Above all, I just wanted to convey it to you.
> That's the reason why I sent it to you alone.

Usenet is a public forum for open discussion.

--
Lew
From: Patricia Shanahan on 10 Mar 2010 09:45
Joshua Cranmer wrote:
> On 03/10/2010 12:53 AM, Javas wrote:
>> Why does the above code results in a compilation error? since it is
>> always invoking class B's process() method which doesnt throw any
>> exception.
>
> How can the compiler know that you're only invoking B's method?
>

In this case the compiler *could* know through data flow analysis. The
method invocation is dominated by the assignment of the result of a B
instance creation to the invocation's target reference.

In order to avoid situations in which a program is considered valid by
one compiler but rejected by another, the compile time error rules are
written up in the JLS. Allowing the example program would require a set
of rules at least as complicated as the definite assignment rules at
http://java.sun.com/docs/books/jls/third_edition/html/defAssign.html.

The benefit would be far smaller, and would destroy the advantage of
declaring the variable with a supertype. If the programmer intends the
reference to be required to refer to a B, and treated by the compiler as
always referring to a B, it should be declared as type B. The usual
motive for using a supertype such as A is to ensure that the code does
not take advantage of the variable always referring to a B, and would
continue to work if "new B()" were replaced by an expression referring
to an A or to any subclass of A. Data flow analysis acceptance of the
example would destroy that benefit.

Patricia
From: Jeff KE7NVY on 10 Mar 2010 11:49
On Mar 9, 9:53 pm, Javas <deepan...(a)gmail.com> wrote:
> public class Qn24 {
>
>         static class A
>         {
>                 void process() throws Exception { throw new
> Exception(); }
>         }
>
>         static class B extends A
>         {
>                 void process() { System.out.println("B "); }
>         }
>
>         public static void main(String[] args)
>         {
>                 A a = new B();
>                 a.process();
>         }
>
> }
>
> Why does the above code results in a compilation error? since it is
> always invoking class B's process() method which doesnt throw any
> exception.

Exception is a checked exception. That means that whenever you
declare
a method that (potentially) throws it, you must do one of two things
in
the code that calls that method. Either handle the exception by
putting
the call inside a try/catch block:

public static void main(String[] args) {
A a = new B();
try {
a.process();
}
catch (Exception e) {
System.out.println("main: Exception caught");
}
}

Or, declare the calling method as also throwing Exception:

public static void main(String[] args) throws Exception {
A a = new B();
a.process();
}
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