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Groups > comp.lang.java.programmer > #18615

Re: Objects only passed by copy?

From Roedy Green <see_website@mindprod.com.invalid>
Newsgroups comp.lang.java.programmer
Subject Re: Objects only passed by copy?
Date 2012-09-08 19:57 -0700
Organization Canadian Mind Products
Message-ID <ob1o485fcnj7gdhi596om6dghp4adfun8h@4ax.com> (permalink)
References <6e06860b-4c72-4f4b-8892-69aa4242a4dc@googlegroups.com>

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On Sat, 8 Sep 2012 17:22:05 -0700 (PDT), Luft <edamron@spamcop.net>
wrote, quoted or indirectly quoted someone who said :

>I'm learning JAVA and read that EVERYTHING in
 JAVA is passed by copy and that in the case of objects the internal
variables share a reference but that objects are also passed by copy.
>
>I'm trying to think of a piece of code that would demonstrate
 this but can't think of anything off the top of my head.

 that is not correct. Objects are not cloned.  References to single
object as passed around. 

Write a method that takes an object parameter with a mutable field.
Change it in the method.  If it copied, you would see the mother
object changed as well. You won't.

see http://mindprod.com/jgloss/object.html
and follow links

This drives you crazy as a newbie, but once you get it is seems so
easy and so obvious, it is hard to understand why you had so much
trouble.  
-- 
Roedy Green Canadian Mind Products http://mindprod.com
A new scientific truth does not triumph by convincing its opponents and making them see the light,
but rather because its opponents eventually die, and a new generation grows up that is familiar with it.
~ Max Planck 1858-04-23 1947-10-04 

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Thread

Objects only passed by copy? Luft <edamron@spamcop.net> - 2012-09-08 17:22 -0700
  Re: Objects only passed by copy? Arne Vajhøj <arne@vajhoej.dk> - 2012-09-08 20:59 -0400
    Re: Objects only passed by copy? Arne Vajhøj <arne@vajhoej.dk> - 2012-09-08 21:02 -0400
  Re: Objects only passed by copy? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-09-08 21:30 -0400
    Re: Objects only passed by copy? Lew <lewbloch@gmail.com> - 2012-09-30 17:23 -0700
  Re: Objects only passed by copy? Roedy Green <see_website@mindprod.com.invalid> - 2012-09-08 19:57 -0700
    Re: Objects only passed by copy? Roedy Green <see_website@mindprod.com.invalid> - 2012-09-30 13:50 -0700

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