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Subject: Re: hashCode
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From: =?UTF-8?B?QXJuZSBWYWpow7hq?= <arne@vajhoej.dk>

On 8/11/2012 10:15 PM, Arne Vajh-,j wrote:
> This is a classic test question in basic Java SE. And that returning
> a constant is correct but not smart should be in most Java SE
> text books.

Effective Java / Joshua Bloch:

<quote>
// The worst possible legal hash function - never use!
public int hashCode() { return 42; }

It is legal because it ensures that equal objects have the same hash code. It's 
atrocious because ...
</quote>

Java 2 SUN Certified Programmer & Developer / Kathy Sierra & Bert Bates:

<quote>
A hashCode() that returns the same value for all instances whether they're 
equal or not is still a legal - even appropriate - hashCode() method! For 
example,
public int hashCode() {
     return 1492;
}
would not violate the contract
...
This hashCode() method is horrible inefficient, ... ...
Nontheless, this one-hash-fits-all method would be considered appropriate and 
even correct because it doesn't violate the contract. Once more, correct does 
not necessarily mean good.
</quote>

Arne

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