HashCodeBuilder.hashCode() should return the same value as
HashCodeBuilder.toHashCode()
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Key: LANG-520
URL: https://issues.apache.org/jira/browse/LANG-520
Project: Commons Lang
Issue Type: Improvement
Affects Versions: 2.4
Reporter: Paul Martin
Priority: Minor
HashCodeBuilder's toHashCode() method must currently be used to generate the
calculated hash code value for an object. However, this method name
('toHashCode') is very similar to the standard 'hashCode()' method, which will
just return the (default) hash code of the HashCodeBuilder object itself.
Since these names are so similar (and otherwise have the same signature), they
are easy to confuse. If this happens, then the hashCode used for an object
will be that of the HashCodeBuilder, which then will probably not be compatible
with its 'equals' implementation. This may result in serious bugs (e.g. memory
leaks when combined with ToStringBuilder - see LANG-453).
I suggest either:
- Implement HashCodeBuilder.hashCode() to return the same value as
.toHashCode() (maybe with a logged warning), in which case it will not matter
if the wrong method is called. This will still be compatible with
HashCodeBuilder's equals/hashCode contract, since equals is not implemented,
and should therefore be relatively backwards-compatible (though the hashCode
will now change as calls are made to HashCodeBuilder).
- Throw an UnsupportedOperationException in hashCode(). This is more likely to
break existing code though.
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