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From Spark Shen <smallsmallor...@gmail.com>
Subject Re: [classlib] Sun compiler change?
Date Tue, 29 Aug 2006 03:38:22 GMT
Krzysztof Sobolewski 写道:
> Spark Shen wrote:
>> Did you (refer to thread [app] ant with ecj) put
>> Eclipse compiler JAR on Ant's
>> execution classpath to execute the javac task.
>> If so, may be that's why It always gives you "unchecked cast" warning,
>> no errors.
> Well, I created a new EnumSet class in completly unrelated environment... So
> it is perfectly possible that there's a classpath conflict somewhere. I
> can't verify that because don't have the Harmony build here :)
> BTW: another experiment revealed that
> EnumSet<? extends Enum<E>> set = (EnumSet<? extends Enum<E>>)collection;
> compiles without warnings. No matter how much I think I understand generics,
> there's always something that surprises me ;)
Conceptually speaking, I think EnumSet<? extends Enum<E>> still has 
potential pitfall:

In the signature of addAll(Collection<? extends E> collection) method, ? 
denotes subclass of E.
While in EnumSet<? extends Enum<E>>, ? denotes subclass of Enum<E>. But

consider the relationship
between E and Enum<E>, E is subclass of Enum<E>. So, we can not 
guarantee that subclass of E is definitely
subclass of Enum<E>.

Correct me if I am wrong.

Best regards
> -KS

Spark Shen
China Software Development Lab, IBM

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