Does someone understand why this works this way? This seems so odd. I know
there are quirks to the generics syntax, but this in an edge I haven't run
into yet. I haven't been able to make this one click in my head yet.
This compiles fine:
public synchronized void putAll(Map<? extends K,? extends V> map) {
for (Map.Entry<? extends K,? extends V> entry : map.entrySet()) {
...
}
}
This won't compile at all:
public synchronized void putAll(Map<? extends K,? extends V> map) {
Set<Map.Entry<? extends K, ? extends V>> entries = map.entrySet();
...
}
The error is: Type mismatch: cannot convert from Set<Map.Entry<capture-of ?
extends K,capture-of ? extends V>> to Set<Map.Entry<? extends K,? extends
V>>
The suggested quick fix in Eclipse is "Set<?> entries = ...".
This reports a warning:
public synchronized void putAll(Map<? extends K,? extends V> map) {
Map<K,V> map2 = (Map<K,V>)map;
}
The warning is: Type safety: The cast from Map<capture-of ? extends
K,capture-of ? extends V> to Map<K,V> is actually checking against the
erased type Map
The suggested quick fix in Eclipse is to the annotation:
@SuppressWarnings("unchecked").
-Nathan
> -----Original Message-----
> From: Tim Ellison [mailto:[EMAIL PROTECTED]
> Sent: Wednesday, May 10, 2006 6:59 AM
> To: [email protected]
> Subject: Thanks Stepan! (was: Re: [jira] Resolved: (HARMONY-454)
> [classlib][luni] java.util.Set generics uplift and related changes)
>
> Stepan Mishura (JIRA) wrote:
> <snip>
> > 2) To avoid casting while-loop was replaced with for-loop. Could you
> review the change?
>
> I was scratching my head about this cast, so I was very pleased to see
> your elegant solution.
>
> I must admit that I don't really understand why the for-loop version is
> inherently different (other than it 'hides' the casting) -- but I've
> learned a new pattern there :-)
>
> Regards,
> Tim
>
> --
>
> Tim Ellison ([EMAIL PROTECTED])
> IBM Java technology centre, UK.
>
>
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