Re: hashCode

From:

"Eric Sosman" <eric.sosman@1:261/38.remove-6fd-this>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 12 Aug 2012 20:00:36 GMT

Message-ID:

<5027FE12.56709.calajapr@time.synchro.net>

To: Patricia Shanahan
From: Eric Sosman <esosman@ieee-dot-org.invalid>

On 8/12/2012 12:40 PM, Patricia Shanahan wrote:

[...]
I think there are two reasonably usable ways of handling this issue. One
is the current arrangement, in which every class has a hashCode that is
expected to be usable for selecting a hash table bucket.

Keeping hashCode as an Object method but making it useless for bucket
selection unless overridden would not be a good alternative.

A more reasonable alternative would be to have hashCode as the only
member of a HashKey interface that would be implemented by every class
whose objects are intended to be suitable for use as has keys. Those
objects that have a hashCode would still have to have a usable one, but
some classes would not implement HashKey and not have a hashCode at all.

Ugh. So if J. Random Programmer is too lazy or unimaginative to
write hashCode(), that means I can't use his class as a HashMap key, or even
put instances in a HashSet? Ugh, again.

(And, no: I don't think a HashCalculator interface along the lines
of Comparable would save the day.)

--
Eric Sosman
esosman@ieee-dot-org.invalid

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