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Posted to dev@commons.apache.org by Bastian Helfert <ba...@web.de> on 2004/12/20 00:38:59 UTC
[collections] Classes that decorate collections with References?
If wished and/or needed, I would like to contribute by writing some
classes that decorate Collections, Lists, Maps and/or Sets with
Soft-/WeakReferences. These Decorators shall make the Reference handling
transparent to the user. Besides having
org.apache.commons.collections.map.AbstractReferenceMap and
java.util.WeakHashMap, I could imagine that having i.e. Lists that
contain WeakReferences to listener objects would be useful. What do you
think?
Bastian
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Re: [collections] Classes that decorate collections with References?
Posted by Chris Lambrou <ma...@chrislambrou.com>.
Stephen Colebourne wrote:
> I am unsure as to the use case for a ReferenceList/ReferenceSet. We
> already have ReferenceMap, which is very useful for building caches,
> but why would you need a List/Set? How would they operate?
Well, here's an example, off the top of my head. A weakly referencing
list could be useful for implementing the observer pattern in a
situation where you don't want the listeners to be strongly referenced
by the event source. If the event source uses such a list to hold its
listeners, then as long as the listeners remain strongly referenced,
they will continue to receive events from the source. There will be no
need to explicitly unregister the listeners, as once they become weakly
referenced, then they will effectively be removed from the event
listener list automatically.
Chris
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Re: [collections] Classes that decorate collections with References?
Posted by Chris Lambrou <ma...@chrislambrou.com>.
Stephen Colebourne wrote:
> I am unsure as to the use case for a ReferenceList/ReferenceSet. We
> already have ReferenceMap, which is very useful for building caches,
> but why would you need a List/Set? How would they operate?
Well, here's an example, of the top of my head. A weakly referencing
list could be useful for implementing the observer pattern in a
situation where you don't want the listeners to be strongly referenced
by the event source. If the event source uses such a list to hold its
listeners, then as long as the listeners remain strongly referenced,
they will continue to receive events from the source. There will be no
need to explicitly unregister the listeners, as once they become weakly
referenced, then they will effectively be removed from the event
listener list automatically.
Chris
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Re: [collections] Classes that decorate collections with References?
Posted by Stephen Colebourne <sc...@btopenworld.com>.
I am unsure as to the use case for a ReferenceList/ReferenceSet. We already
have ReferenceMap, which is very useful for building caches, but why would
you need a List/Set? How would they operate?
Stephen
----- Original Message -----
From: "Bastian Helfert" <ba...@web.de>
> If wished and/or needed, I would like to contribute by writing some
> classes that decorate Collections, Lists, Maps and/or Sets with
> Soft-/WeakReferences. These Decorators shall make the Reference handling
> transparent to the user. Besides having
> org.apache.commons.collections.map.AbstractReferenceMap and
> java.util.WeakHashMap, I could imagine that having i.e. Lists that contain
> WeakReferences to listener objects would be useful. What do you think?
>
> Bastian
>
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> To unsubscribe, e-mail: commons-dev-unsubscribe@jakarta.apache.org
> For additional commands, e-mail: commons-dev-help@jakarta.apache.org
>
>
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