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Groups > comp.lang.java.programmer > #10116
| From | Eric Sosman <esosman@ieee-dot-org.invalid> |
|---|---|
| Newsgroups | comp.lang.java.programmer |
| Subject | Re: Size of an arraylist in bytes |
| Date | 2011-11-20 16:30 -0500 |
| Organization | A noiseless patient Spider |
| Message-ID | <jabri2$763$1@dont-email.me> (permalink) |
| References | <e9dcfb2d-dfef-4ae6-9d9f-979a8f08b962@t36g2000prt.googlegroups.com> |
On 11/20/2011 4:01 PM, sara wrote:
> Hi All,
>
> I create an Arraylist<Integer> tmp and add some integers to it.
> Afterward, I measure the size of tmp in bytes (by converting tmp to
> bytes array). Assume the result is byte[] C. However, when I update an
> element of tmp, and measure size of tmp in bytes again, the result is
> different than C!
> Why this is the case?
See markspace's response. Another possible point of confusion:
The ArrayList does not actually contain objects, but references to
those objects -- that's why the same object instance can be in three
ArrayLists, two Sets, and a Map simultaneously. In fact, the same
Integer object could appear forty-two times in a single ArrayList:
List<Integer> list = new ArrayList<Integer>();
Integer number = Integer.valueOf(42);
for (int i = 0; i < 42; ++i)
list.add(number);
If you're coming from a C background, a rough analogy is that
the ArrayList holds "pointers" to the objects it holds, not copies
of those objects.
--
Eric Sosman
esosman@ieee-dot-org.invalid
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Size of an arraylist in bytes sara <sarasara82@gmail.com> - 2011-11-20 13:01 -0800
Re: Size of an arraylist in bytes markspace <-@.> - 2011-11-20 13:05 -0800
Re: Size of an arraylist in bytes sara <sarasara82@gmail.com> - 2011-11-20 13:11 -0800
Re: Size of an arraylist in bytes Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-11-20 21:58 +0000
Re: Size of an arraylist in bytes markspace <-@.> - 2011-11-20 14:08 -0800
Re: Size of an arraylist in bytes Patricia Shanahan <pats@acm.org> - 2011-11-20 14:50 -0800
Re: Size of an arraylist in bytes Arne Vajhøj <arne@vajhoej.dk> - 2011-11-20 18:06 -0500
Re: Size of an arraylist in bytes Lew <lewbloch@gmail.com> - 2011-11-20 20:28 -0800
Re: Size of an arraylist in bytes Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-11-20 16:30 -0500
Re: Size of an arraylist in bytes sara <sarasara82@gmail.com> - 2011-11-20 13:35 -0800
Re: Size of an arraylist in bytes Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-11-20 17:19 -0500
Re: Size of an arraylist in bytes Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-11-20 16:58 -0500
Re: Size of an arraylist in bytes Patricia Shanahan <pats@acm.org> - 2011-11-20 14:04 -0800
Re: Size of an arraylist in bytes Arne Vajhøj <arne@vajhoej.dk> - 2011-11-20 17:18 -0500
Re: Size of an arraylist in bytes Patricia Shanahan <pats@acm.org> - 2011-11-20 14:48 -0800
Re: Size of an arraylist in bytes Arne Vajhøj <arne@vajhoej.dk> - 2011-11-25 22:12 -0500
Re: Size of an arraylist in bytes Lew <lewbloch@gmail.com> - 2011-11-20 20:44 -0800
Re: Size of an arraylist in bytes Arne Vajhøj <arne@vajhoej.dk> - 2011-11-25 22:16 -0500
Re: Size of an arraylist in bytes Lew <lewbloch@gmail.com> - 2011-11-25 20:15 -0800
Re: Size of an arraylist in bytes Roedy Green <see_website@mindprod.com.invalid> - 2011-11-20 22:25 -0800
Re: Size of an arraylist in bytes Arne Vajhøj <arne@vajhoej.dk> - 2011-11-25 22:11 -0500
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