Re: hashCode

From:

"Lew" <lew@1:261/38.remove-odu-this>

Newsgroups:

comp.lang.java.programmer

Date:

Mon, 13 Aug 2012 19:38:29 GMT

Message-ID:

<50294F00.56788.calajapr@time.synchro.net>

  To: Jan Burse
From: "Lew" <lew@1:261/38.remove-nlb-this>

  To: Jan Burse
From: "Lew" <lew@1:261/38.remove-m2z-this>

  To: Jan Burse
From: Lew <noone@lewscanon.com>

Jan Burse wrote:

Maybe it would make sense to spell out what the contract
for hashCode() is. Well the contract is simply, the
following invariant should hold:

/* invariant that should hold */
if a.equals(b) then a.hashCode()==b.hashCode()

True, but if you read the specification for 'hashCode()' fully, that is not the
entire contract, only the compiler-enforceable part of it.

The entire specification requires that as much as feasible, the 'Object'
implementation distinguish distinct instances, and that the method generally
support 'HashMap', which promises O(1) 'get()' and 'put()' with a "proper"
(i.e., compliant) 'hashCode()'.

--
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg

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