Re: hashCode

From:

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

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 12 Aug 2012 13:59:07 -0400

Message-ID:

<k08qtk$j7i$1@dont-email.me>

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