Re: Be Honest: Do you implement hashCode(), equals(), and toString() for every class you write?

From:

Patricia Shanahan <pats@acm.org>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 15 Sep 2006 21:51:30 GMT

Message-ID:

<CfFOg.12105$bM.6744@newsread4.news.pas.earthlink.net>

AndrewMcDonagh wrote:

Mark Jeffcoat wrote:

"Danno" <dh.evolutionnext@gmail.com> writes:

Just curious

You'll know when you need equals()... most things
don't get compared, so there's usually no reason to bother.
Once you've put in your own equals() method, you really
need to override hashCode(), too. But pre-mature optimization
is evil, so here's the one I always use pre-profiling:

    public int hashCode() {
        return 0;
    }

I'm not kidding.

If thats your over ridden version - your application would be better
served not doing anything. At least that way you may get some
distribution of the objects within a Hash. With your current approach
your Hashes would always only contain one bucket full of every instance.

Distributing the objects within the hash is very, very bad unless you
ensure that any pair of equal objects have the same hash code.

You are in effect causing a performance problem - not optimizing a slow
one.

He is not trying to optimize. He is trying to maintain program
correctness, and do optimization later, if it is needed.

Patricia