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https://issues.apache.org/jira/browse/COLLECTIONS-467?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13655585#comment-13655585
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Thomas Neidhart commented on COLLECTIONS-467:
---------------------------------------------
The LRUMap already provides a functionality for this, see the javadoc of the
removeLRU method:
{noformat}
* Subclass method to control removal of the least recently used entry from
the map.
* <p>
* This method exists for subclasses to override. A subclass may wish to
* provide cleanup of resources when an entry is removed. For example:
* <pre>
* protected boolean removeLRU(LinkEntry entry) {
* releaseResources(entry.getValue()); // release resources held by entry
* return true; // actually delete entry
* }
* </pre>
{noformat}
This method is protected and can be overriden by subclasses in the same way as
your proposed onAdd and onRemove methods.
In case you deliberately remove elements with remove / clear, you are aware of
the element removal, so you can take care of releasing the resources imho (or
at least override remove/clear in such a case if you prefer that).
There is another proposal for a TrackingCollection (see COLLECTIONS-248) which
is somehow similar, in the sense that it keeps track of all additions/removals
to a collection. Maybe it would make sense to add such a MapDecorator.
> LRUMap remove callback
> ----------------------
>
> Key: COLLECTIONS-467
> URL: https://issues.apache.org/jira/browse/COLLECTIONS-467
> Project: Commons Collections
> Issue Type: New Feature
> Affects Versions: 3.2
> Reporter: l0co
> Priority: Minor
>
> If you use LRUMap with objects that require doing some disposal when they are
> dropped (eg. close()) and you hold these objects only in LRUMap, you cannot
> do it with current implementation. I propose to add onRemove() and onAdd()
> methods to the implementation, so that you can create anonymous inherited
> class and be able to react to these events.
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