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Groups > comp.lang.java.programmer > #10115

Re: Size of an arraylist in bytes

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Here is the code:

		ArrayList<Integer> tmp=new ArrayList<Integer>();
		tmp.add(-1);
		tmp.add(-1);
		System.out.println(DiGraph.GetBytes(tmp).length);
		tmp.set(0, 10);
		System.out.println(DiGraph.GetBytes(tmp).length);


	public static byte[] GetBytes(Object v) {
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
		ObjectOutputStream oos;
		try {
			oos = new ObjectOutputStream(bos);
			oos.writeObject(v);
			oos.flush();
			oos.close();
			bos.close();
		} catch (IOException e) {
			e.printStackTrace();
		}
		byte[] data = bos.toByteArray();
		return data;
	}

The problem is I need to write multiple arraylists on disk and later
on I update the elements of them. I store the starting location of
arraylists and their size such that later I can refer to them. If the
size of objects change then it messes up! Could you please help?
On Nov 20, 1:05 pm, markspace <-@.> wrote:
> On 11/20/2011 1:01 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?
>
> We'd have to see some code to give you a good answer, but basically you
> can't measure the memory size of Java objects.  They change over time,
> in ways that C or C++ can't or doesn't, and there's not much to do that
> can rectify that.

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Thread

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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