Re: hashCode
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From: "Lew" <lew@1:261/38.remove-nlb-this>
To: =?UTF-8?B?QXJuZSBWYWpow7hq?=
From: "Lew" <lew@1:261/38.remove-m2z-this>
To: =?UTF-8?B?QXJuZSBWYWpow7hq?=
From: Lew <noone@lewscanon.com>
Arne Vajh-,j wrote:
The original questions were:
#Is it always technically correct to override the hashCode function #like so:
#
# @Override
# public int hashCode() {
# return 1;
# }
For which the answer is YES. Per documentation.
But with really poor performance in many relevant cases.
#Would it be potentially better if that was Object's implementation?
Which was clarified to:
#Better in the sense that you would never HAVE to override hashCode.
For which the answer is also YES. Per the previous.
No, that's not true. Value-equality maps, for example, would not work if you
didn't override 'hashCode()' in the key type to match value equality on the
keys.
But with the same performance note. And a big sigh because it
seems to want to broaden bad performance from a single class
to the entire programming style (multiple classes).
Overriding 'hashCode()' is done for functional reasons, not performance
reasons. If you fail to override the method, you'll get incorrect behavior, for
example failing to find a collection member that is actually present.
--
Lew
Honi soit qui mal y pense.
http://upload.wikimedia.org/wikipedia/commons/c/cf/Friz.jpg
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