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https://issues.apache.org/jira/browse/COLLECTIONS-148?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Thomas Neidhart updated COLLECTIONS-148:
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Fix Version/s: (was: 4.0-beta-1)
4.0
> [collections] Change to HashEntry inner class of AbstractHashedMap
> ------------------------------------------------------------------
>
> Key: COLLECTIONS-148
> URL: https://issues.apache.org/jira/browse/COLLECTIONS-148
> Project: Commons Collections
> Issue Type: Improvement
> Environment: Operating System: other
> Platform: All
> Reporter: Henry Story
> Priority: Minor
> Fix For: 4.0
>
> Attachments: collections-altered.jpg, collections.jpg, hashed.tar,
> patch.txt
>
>
> The way the AbstractHashedMap class is currently written it is not as
> extensible as it could be.
> The HashEntry static inner class is abstract. By slightly refactoring it to
> an inner interface one can get a
> lot more mileage out of it.
> This change has minimal impact on four other classes from the map package.
> Two extra classes which I will submit as a seperate patch (should I do this
> before this one is accepted?)
> that use this inner interface are a HashedSet and a WeakHashedSet. Both of
> these classes are adapters
> of a subclass of the changed AbstractHashedMap.
> The HashEntry interface essentially hides the representation of the key and
> value objects. In a HashSet
> the key is the value, so this avoids the duplication - not of objects, but of
> references. More importantly
> it also allows a HashEntry to extend a WeakReference Object, which cannot be
> done as the code
> presently stands.
> Here is the new interface:
> protected static interface HashEntry extends Map.Entry, KeyValue {
> public HashEntry getNext();
> public void setNext(HashEntry next);
> public int getHashCode();
> public void setHashCode(int hashCode);
> /**
> * @param key raw key (ie, no interpretation for special cases like
> NULL
> */
> public void setRawKey(Object key);
> /**
> *
> * @return the raw key
> */
> public Object getRawKey();
> }
> This allows the implementation to decide how they can refer to the key and
> the values. Essentially we
> remove all reference in the code to the variables 'key' and 'value' and
> replace them with the (set/
> get)rawkey (set/get)value methods. The raw key method is necessary as the
> setKey method is often
> overridden to do special null substition work.
> I have also created a more interesting NULL object, that can better describe
> itself. When debugging it is
> often helpful to know that one is looking at a NULL object.
> Finally I also - and debatably wrongly - changed the Iterator from static
> inner classes to real inner
> classes. This is how it is meant to work anyway. An inner class just has a
> reference to its enclosing
> class. But perhaps there is something here that I have not understood. My
> other contributions don't
> hang on this change. They just make the code a little simpler.
> If the intention is to extract these classes to an external package, then the
> current solution of having a
> static inner class makes sense.
> I will attach class diagrams and diffs to this request to clarify the changes.
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