Jörn Kottmann wrote:
>
> On Aug 7, 2009, at 8:57 PM, Marshall Schor wrote:
>
>> getViewIterator in CASImpl is written with the signature:
>> Iterator<CAS> getViewIterator()
>>
>> If you are working with things needing CASImpl objects, you would write:
>>
>> Iterator<CAS> s = aCas.getViewIterator();
>> while (s.hasNext()) {
>> CASImpl ci = (CASImpl) s.next();
>> ... code using ci...
>> }
>>
>> If we changed the signature to:
>> Iterator<T extends CAS> getViewIterator()
>> then you would write:
>> Iterator<CASImpl> s = aCas.getViewIterator(); // cast done inside the
>> support code, not here
>> while (s.hasNext()) {
>> CASImpl ci = s.next(); // works OK without casting
>> ... code using ci...
>> }
>>
>> Would it be better to have that form of the signature?
>
> +1, though did not know that its possible, we should check other
> places too
+1 to checking other places :-)
The tutorial on generics by Gilad Bracha,
http://java.sun.com/j2se/1.5/pdf/generics-tutorial.pdf, on page 20 near
the top says:
> In general, if you have an API that only uses a type parameter T as an
> argument, its
> uses should take advantage of lower bounded wildcards (? super T).
> Conversely, if
> the API only returns T, you’ll give your clients more flexibility by
> using upper bounded
> wildcards (? extends T).
There are many cases I think in our generification where the 2nd part of
this, returning XXX<? extends T> or a variant, is a better choice.
-Marshall
>
>
> Jörn
>
>
>
