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https://issues.apache.org/jira/browse/MATH-786?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13269075#comment-13269075
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Gilles commented on MATH-786:
-----------------------------
OK.
Then assuming that it's the user's responsibility to not mutate the passed
references, it seems reasonable to _optionally_ allow the performance gain of
computing the hash code at construction, by having a flag in the constructor's
parameter list:
{noformat}
public Pair(K k, V v, boolean assumeImmutable) {
key = k;
value = v;
immutable = assumeImmutable;
hashCode = computeHashCode();
}
{noformat}
Then, we'd have:
{noformat}
public int hashCode() {
return immutable ? hashCode : computeHashCode();
}
{noformat}
What do you think?
> "hashCode" in "Pair" class
> --------------------------
>
> Key: MATH-786
> URL: https://issues.apache.org/jira/browse/MATH-786
> Project: Commons Math
> Issue Type: Improvement
> Affects Versions: 3.0
> Reporter: Gilles
> Assignee: Gilles
> Priority: Trivial
> Fix For: 3.1
>
>
> Since "Pair" is supposed to be an immutable class, couldn't we cache the
> "hashCode" value at construction? That would supposedly make it more
> efficient when used in maps.
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