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From "Clinton Begin" <clinton.be...@gmail.com>
Subject Re: Does iBatis use or support Generics ?
Date Tue, 13 Mar 2007 14:48:31 GMT
I guess we'll have to disagree.  I'm not against generics entirely, just
Java's implementation is screwy.   I know it's for backward compatibility,
but I really wonder....why bother.

>> i.e. allows the compiler to perform stricter static type cheking?

VERY VERY minimal.

List<String> strings = new ArrayList<String>();
List unknown = strings; //it only takes one to break the chain
List<Integer> integers = unknown;

>> i.e. is safer?

No, all the errors are in the exact same place.  Using the code above, if I
use

Integer i = integers.get(0);

I get the same ClassCastException as if I had:

Integer i = (Integer) unknown.get(0);

>> i.e. is more (human) readable?

Well, using your example it's only more readable because the variable name
wasn't descriptive.  If you had rename "myFactory"  to "stringList", they
are both descriptive and readable.  The nice thing is that the variable name
is more readable everywhere, not just on the declaration.

Also, in my example above, I think the cast is more readable, only because
that's where the error will happen.  With the generic list it makes me
wonder "WTF happened?  I thought this was a typesafe generic list that could
only have integers!".  Which of course is not the case at all.

One old API will completely eliminate the type safety.   And it will be
years before all APIs give full respect to generic types.

Don't get me wrong, iBATIS will support them.  And as syntactic sugar
they're nice in some ways.  But nobody should be fooled.  They are not
safer.

If you get a chance to attend NFJS, Venkat explains it best:

http://www.nofluffjuststuff.com/speaker_topic_view.jsp?topicId=78

Cheers,
Clinton


On 3/13/07, c.zecca@ads.it <c.zecca@ads.it> wrote:
>
> "Clinton Begin" <clinton.begin@gmail.com> scritti il 13/03/2007 14:42:04
>
> > How is it safer?
>
> Let's assume to read the interface for the our factory (object loader)
>
> List
> myFactory( ... );
>
> List<String>
> myFactory(...);
>
>
> Which of the two signatures provides better information?
> i.e. allows the compiler to perform stricter static type cheking?
> i.e. is safer?
> i.e. is more (human) readable?
>
> Of course internally (within the factory) we have to perform one cast.
> List<Strings> allows the client code use the list of looaded strings with
> its correct type
> without any (dangerous) casting.
>
>
> > In both cases the error occurs at runtime at the exact same point in
> > the code.  And at runtime both are turned into a cast anyway.
> That's right.
> Exactly the minimum, i.e. one and only one casting, no more.
> A cast in necessary somewhere internally to the factory/loader.
> Externally is much better to use a generic container along with its actual
> type.
> I think that we agree.
>
> ciao
>

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