Re: do I need to override the equals() method?

From:

"Mike Schilling" <mscottschilling@hotmail.com>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 3 Apr 2009 16:53:22 -0700

Message-ID:

<GgxBl.4850$Lr6.2333@flpi143.ffdc.sbc.com>

"Lew" <noone@lewscanon.com> wrote in message
news:gr546m$s00$1@news.albasani.net...

Joshua Bloch covers this in /Effective Java/, a book you must own.

Always override 'equals()' and 'hashCode()' together if at all. Make sure
they are consistent with each other, i.e., if two instances compare equal,
they must have the same hash code. (The converse is not true.) Make sure
you involve each field that logically affects value equality.

For example, in comparing instances of a hypothetical 'Person' class, you
might involve 'nationalID' (e.g., Social Security number). Or you might
compare a combination of 'birthName', 'birthDate', 'birthPlace',
'birthGender' and 'disambiguator'. The same field(s) would be involved in
both the 'equals()' and 'hashCode()' methods.

It occurs to me that something I'd like in an IDE is for it to let me mark
the fields that consititute my unique key, and then it can generate equals()
and hashCode() . The process is mechanical enough for the result to be at
least 90% correct.