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Groups > comp.lang.java.programmer > #20436
| Date | 2012-12-18 10:39 +0000 |
|---|---|
| From | lipska the kat <lipskathekat@yahoo.co.uk> |
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Need clarification on Object.equals. |
| References | <e6f674ec-f00d-4b22-bc02-e1c0ff9ff196@oi3g2000pbb.googlegroups.com> |
| Message-ID | <d8WdnQ4s7tp82k3NnZ2dnUVZ8smdnZ2d@bt.com> (permalink) |
On 18/12/12 08:13, plewto@gmail.com wrote:
> In the following code Node is an abstract class and both Gate and
> Monitor are extensions of Node. a and b are distinct objects yet
> a.equals(b) is returning true.
>
> public class Foo {
> public static void main(String[] argv){
> Node a = new Gate();
> Monitor b = new Monitor();
> System.out.println(a.equals(b)); // --> prints 'true'
> }
> }
According to the documentation the contract for equals on instances of
class Object is as follows
"The equals method for class Object implements the most discriminating
possible equivalence relation on objects; that is, for any non-null
reference values x and y, this method returns true if and only if x and
y refer to the same object (x == y has the value true)."
This is obviously the not the case in your example above.
Does the class Node or any of it's superclasses override the equals method ?
The following code returns false as expected
public abstract class Foo {
public static void main(String args[]){
Foo bar = new Bar();
Baz baz = new Baz();
System.out.println(bar.equals(baz));
}
}
class Bar extends Foo{}
class Baz extends Foo{}
...
However, add the following method to the class Foo
public boolean equals(Object obj){
return true;
}
and re-run the code and we get true.
Has someone been messing with equals ?
lipska
--
Lipska the Kat©: Troll hunter, sandbox destroyer
and farscape dreamer of Aeryn Sun
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Need clarification on Object.equals. "plewto@gmail.com" <plewto@gmail.com> - 2012-12-18 00:13 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-18 10:39 +0000
Re: Need clarification on Object.equals. Roedy Green <see_website@mindprod.com.invalid> - 2012-12-18 04:48 -0800
Re: Need clarification on Object.equals. Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2012-12-18 10:56 -0800
Re: Need clarification on Object.equals. FredK <fred.l.kleinschmidt@gmail.com> - 2012-12-19 08:13 -0800
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 11:22 -0500
Re: Need clarification on Object.equals. Lars Enderin <lars.enderin@telia.com> - 2012-12-19 17:43 +0100
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 12:06 -0500
Re: Need clarification on Object.equals. Patricia Shanahan <pats@acm.org> - 2012-12-19 09:39 -0800
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 13:24 -0500
Re: Need clarification on Object.equals. FredK <fred.l.kleinschmidt@gmail.com> - 2012-12-19 11:23 -0800
Re: Need clarification on Object.equals. Patricia Shanahan <pats@acm.org> - 2012-12-19 08:25 -0800
Re: Need clarification on Object.equals. plewto@gmail.com - 2012-12-18 10:56 -0800
Re: Need clarification on Object.equals. Jim Janney <jjanney@shell.xmission.com> - 2012-12-18 14:24 -0700
Re: Need clarification on Object.equals. Patricia Shanahan <pats@acm.org> - 2012-12-18 13:52 -0800
Re: Need clarification on Object.equals. markspace <-@.> - 2012-12-18 10:24 -0800
Re: Need clarification on Object.equals. plewto@gmail.com - 2012-12-18 10:48 -0800
Re: Need clarification on Object.equals. David Lamb <dalamb@cs.queensu.ca> - 2012-12-18 14:01 -0500
Re: Need clarification on Object.equals. plewto@gmail.com - 2012-12-18 12:14 -0800
Re: Need clarification on Object.equals. plewto@gmail.com - 2012-12-18 12:17 -0800
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-18 22:16 -0500
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 10:20 +0000
Re: Need clarification on Object.equals. Patricia Shanahan <pats@acm.org> - 2012-12-19 03:22 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 12:06 +0000
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 09:07 -0500
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 09:09 -0500
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 14:36 +0000
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 09:42 -0500
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 15:05 +0000
Re: Need clarification on Object.equals. Lars Enderin <lars.enderin@telia.com> - 2012-12-19 16:15 +0100
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 15:47 +0000
Re: Need clarification on Object.equals. Lars Enderin <lars.enderin@telia.com> - 2012-12-19 16:57 +0100
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 16:51 +0000
Re: Need clarification on Object.equals. Lars Enderin <lars.enderin@telia.com> - 2012-12-19 18:12 +0100
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 17:27 +0000
Re: Need clarification on Object.equals. Gene Wirchenko <genew@telus.net> - 2012-12-19 11:40 -0800
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 10:17 -0500
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 15:40 +0000
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 10:50 -0500
Re: Need clarification on Object.equals. Lars Enderin <lars.enderin@telia.com> - 2012-12-19 17:01 +0100
Re: Need clarification on Object.equals. Gene Wirchenko <genew@telus.net> - 2012-12-19 10:22 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 18:49 +0000
Re: Need clarification on Object.equals. Gene Wirchenko <genew@telus.net> - 2012-12-19 11:41 -0800
Re: Need clarification on Object.equals. Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2012-12-19 17:05 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-20 08:34 +0000
Re: Need clarification on Object.equals. Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2012-12-20 07:27 -0800
Re: Need clarification on Object.equals. Gene Wirchenko <genew@telus.net> - 2012-12-20 09:04 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-20 18:10 +0000
Re: Need clarification on Object.equals. Lew <lewbloch@gmail.com> - 2012-12-20 11:08 -0800
Re: Need clarification on Object.equals. Peter Dunihơ <Np0eStPeAdM@NnOwSlPiAnMk.com> - 2012-12-21 07:50 +0000
Re: Need clarification on Object.equals. Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2012-12-21 07:30 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-21 17:09 +0000
Re: Need clarification on Object.equals. Leŵ <lewbl0ch@gmail.com> - 2012-12-23 00:54 +0000
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-21 12:23 -0500
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-21 17:38 +0000
Re: Need clarification on Object.equals. Arne Vajhoj <arne@vajhoj.dk> - 2012-12-23 00:50 +0000
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-21 08:39 +0000
Re: Need clarification on Object.equals. Gene Wirchenko <genew@telus.net> - 2012-12-20 13:39 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-21 08:34 +0000
Re: Need clarification on Object.equals. Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-12-19 09:22 -0600
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 15:35 +0000
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 10:56 -0500
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 17:08 +0000
Re: Need clarification on Object.equals. Joshua Cranmer <Pidgeot18@verizon.invalid> - 2012-12-19 08:58 -0600
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 15:32 +0000
Re: Need clarification on Object.equals. Joshua Cranmer <Pidgeot18@verizon.invalid> - 2012-12-19 11:08 -0600
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 17:32 +0000
Re: Need clarification on Object.equals. Lars Enderin <lars.enderin@telia.com> - 2012-12-19 18:41 +0100
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 17:58 +0000
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 18:12 +0000
Re: Need clarification on Object.equals. Joshua Cranmer <Pidgeot18@verizon.invalid> - 2012-12-19 12:29 -0600
Re: Need clarification on Object.equals. Joshua Cranmer <Pidgeot18@verizon.invalid> - 2012-12-19 12:00 -0600
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 18:06 +0000
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 13:13 -0500
Re: Need clarification on Object.equals. Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2012-12-19 07:48 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 16:48 +0000
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 12:09 -0500
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 17:50 +0000
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 13:14 -0500
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 18:59 +0000
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 13:16 -0500
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 19:05 +0000
Re: Need clarification on Object.equals. Gene Wirchenko <genew@telus.net> - 2012-12-19 11:45 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 20:00 +0000
Re: Need clarification on Object.equals. Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2012-12-19 17:15 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-20 09:22 +0000
Re: Need clarification on Object.equals. Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2012-12-20 07:36 -0800
Re: Need clarification on Object.equals. Gene Wirchenko <genew@telus.net> - 2012-12-19 10:19 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-19 19:16 +0000
Re: Need clarification on Object.equals. Gene Wirchenko <genew@telus.net> - 2012-12-19 11:48 -0800
Re: Need clarification on Object.equals. Leif Roar Moldskred <leifm@dimnakorr.com> - 2012-12-19 14:12 -0600
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 09:04 -0500
Re: Need clarification on Object.equals. Lew <lewbloch@gmail.com> - 2012-12-19 13:40 -0800
Re: Need clarification on Object.equals. lipska the kat <lipskathekat@yahoo.co.uk> - 2012-12-20 09:30 +0000
Re: Need clarification on Object.equals. Lew <lewbloch@gmail.com> - 2012-12-18 12:52 -0800
Re: Need clarification on Object.equals. Joshua Cranmer <Pidgeot18@verizon.invalid> - 2012-12-19 09:27 -0600
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-19 10:44 -0500
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-18 22:11 -0500
Re: Need clarification on Object.equals. Arne Vajhøj <arne@vajhoej.dk> - 2012-12-18 22:10 -0500
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