[Fwd: Code review request: 7072353 JNDI libraries do not build with javac -Xlint:all -Werror]

[Colin Decker]

One better way to handle this in Java 8 would be to have a utility method
that takes a Supplier<Enumeration<E>> SAM argument (with a no-arg method
that returns an Enumeration<E>) and returns an Iterable<E> that gets a new
Enumeration from the supplier each time iterator() is called. It could then
be used with method references:

Iterable<E> iterable = Util.enumerationIterable(#object.getEnumeration);

-- 
Colin


On Wed, Aug 3, 2011 at 5:14 PM, Alexandre Boulgakov <
alexandre.boulgakov at oracle.com> wrote:

> Users of Iterable expect to call Iterable.iterator() multiple times,
> receiving a fresh iterator pointing to the beginning of the Iterable each
> time. This would not be possible to do with an Enumeration wrapper since
> Enumerations are read-once.
>
> I don't know if this is a strong enough reason not to include such a
> utility class, but it could certainly be confusing.
>
> -Sasha
>
>
> On 8/3/2011 2:09 PM, Neil Richards wrote:
>
>> On Wed, 2011-08-03 at 11:03 -0700, Alexandre Boulgakov wrote:
>>
>>> Please see my responses inline.
>>>
>>> Thanks!
>>> -Sasha
>>>
>>> On 8/2/2011 9:13 PM, Xuelei Fan wrote:
>>>
>>>> . com/sun/jndi/toolkit/dir/**SearchFilter.java
>>>>   451         for (NamingEnumeration<?>   ve = attr.getAll();
>>>>   452              ve.hasMore();
>>>>   453                ) {
>>>>
>>>> The update is OK. But the coding style looks uncomfortable. Would you
>>>> mind change it to use for-each style?
>>>>
>>> For-each only works with Iterables. There doesn't seem to be a way to
>>> get an Iterable out of an Attribute instance, so the only way to use a
>>> for-each here would be to wrap the Enumeration in an ArrayList using
>>> Collections.list(). While this might look neater, the contents of the
>>> Enumeration would have to be copied over, using time and increasing the
>>> memory footprint. Changing Attribute to implement Iterable would require
>>> a spec change, and would be beyond the scope of this fix.
>>>
>> Would it  be useful to have a utility object to convert an Enumeration
>> so it can be used in for-each constructs? - something like:
>> ----
>>         import java.util.Enumeration;
>>         import java.util.Iterator;
>>
>>         /**
>>          * Utility class to transform an Enumeration object such that it
>> can be used in
>>          * the for-each construct.
>>          */
>>         public class IterableEnumerationHolder<E>  implements Iterable<E>,
>> Iterator<E>  {
>>             private final Enumeration<E>  e;
>>
>>             public IterableEnumerationHolder(**final Enumeration<E>  e) {
>>                 this.e = e;
>>             }
>>
>>             @Override
>>             public Iterator<E>  iterator() {
>>                 return this;
>>             }
>>
>>             @Override
>>             public boolean hasNext() {
>>                 return e.hasMoreElements();
>>             }
>>
>>             @Override
>>             public E next() {
>>                 return e.nextElement();
>>             }
>>
>>             @Override
>>             public void remove() {
>>                 throw new UnsupportedOperationException(**);
>>             }
>>         }
>> ----
>>
>> If it would, perhaps it might be considered for Java 8?
>>
>> Regards,
>> Neil
>>
>>
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