Groups > comp.lang.java.programmer > #6909

Re: setSize ArrayList, when will it come?

Date	2011-08-09 04:00 -0700
From	Patricia Shanahan <pats@acm.org>
Newsgroups	comp.lang.java.programmer
Subject	Re: setSize ArrayList, when will it come?
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Message-ID	<K6CdnUGfCpfBjtzTnZ2dnUVZ_g6dnZ2d@earthlink.com> (permalink)

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On 8/9/2011 2:16 AM, Jan Burse wrote:
> Patricia Shanahan schrieb:
>> On 8/8/2011 7:16 PM, Jan Burse wrote:
>> ...
>>> I actually do use setSize for a kind of sparse Vector.
>>> Sparse in the sense that my Vector will have a couple
>>> of holes represented by null value elements. Which
>>> is eventually abuse of the term "sparse", but the use
>>> case is there.
>> ...
>>
>> If you only need small numbers of null elements, you could write a class
>> extending ArrayList that has setSize(). All you would do is loop adding
>> null elements or removing the tail elements until the ArrayList is the
>> required size.
>>
>> Patricia
>
> If only so many fields in ArrayList would not be private
> I could do that. But since for example in JDK 1.6.0_26
> none of the fields are protected, everything is private.
>
> What you suggest is theoretically sound but practically
> impossible. Look see:
>
> public class ArrayList<E> extends ...
> {
> private transient Object[] elementData;
> private int size;
> ...
> }
>
> And using reflection overriding this protection,
> is kind of ugly and eventually less performant.

I meant "loop adding null elements" literally.

while(size() < targetSize) {
   add(null);
}

That uses only the public methods size and add. It would not be
efficient for a significantly sparse array, but should work fine if
there are only a few null elements. If there are large blocks of null
elements and efficiency matters, I would use neither Vector nor ArrayList.

Patricia

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setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-09 00:47 +0200
  Re: setSize ArrayList, when will it come? Knute Johnson <september@knutejohnson.com> - 2011-08-08 16:53 -0700
    Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-09 02:30 +0200
  Re: setSize ArrayList, when will it come? Arne Vajhøj <arne@vajhoej.dk> - 2011-08-08 20:50 -0400
  Re: setSize ArrayList, when will it come? Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-08-08 21:09 -0400
    Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-09 04:16 +0200
      Re: setSize ArrayList, when will it come? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-08 21:39 -0500
        Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-09 09:33 +0200
          Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-09 09:42 +0200
        Re: setSize ArrayList, when will it come? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-08-09 07:56 +0000
          Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-09 11:18 +0200
          Re: setSize ArrayList, when will it come? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-09 10:36 -0500
            Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-09 18:30 +0200
              Re: setSize ArrayList, when will it come? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-09 16:30 -0500
                Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-10 00:31 +0200
                Re: setSize ArrayList, when will it come? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-09 20:36 -0500
                Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-10 09:04 +0200
                Re: setSize ArrayList, when will it come? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-08-10 08:50 +0000
                Re: setSize ArrayList, when will it come? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-10 18:16 -0500
                Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-11 01:55 +0200
      Re: setSize ArrayList, when will it come? Patricia Shanahan <pats@acm.org> - 2011-08-09 01:33 -0700
        Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-09 11:16 +0200
          Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-09 11:32 +0200
            Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-09 11:35 +0200
          Re: setSize ArrayList, when will it come? Patricia Shanahan <pats@acm.org> - 2011-08-09 04:00 -0700
          Re: setSize ArrayList, when will it come? Arne Vajhøj <arne@vajhoej.dk> - 2011-08-09 20:11 -0400
      Re: setSize ArrayList, when will it come? Robert Klemme <shortcutter@googlemail.com> - 2011-08-10 10:21 +0200
        Re: setSize ArrayList, when will it come? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-08-10 09:14 +0000
        Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-10 12:29 +0200
          Re: setSize ArrayList, when will it come? Robert Klemme <shortcutter@googlemail.com> - 2011-08-10 19:27 +0200
            Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-10 20:22 +0200
              Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-10 20:37 +0200
                Re: setSize ArrayList, when will it come? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-10 18:22 -0500
                Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-11 01:52 +0200
                Re: setSize ArrayList, when will it come? Joshua Cranmer <Pidgeot18@verizon.invalid> - 2011-08-10 21:43 -0500
                Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-11 14:19 +0200
              Re: setSize ArrayList, when will it come? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-08-10 22:23 +0000
                Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-11 01:47 +0200
                Re: setSize ArrayList, when will it come? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-08-11 00:23 +0000
                Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-11 09:19 +0200
                Re: setSize ArrayList, when will it come? Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2011-08-12 15:06 +0000
  Re: setSize ArrayList, when will it come? Roedy Green <see_website@mindprod.com.invalid> - 2011-08-09 09:58 -0700
    Re: setSize ArrayList, when will it come? Patricia Shanahan <pats@acm.org> - 2011-08-09 10:25 -0700
      Re: setSize ArrayList, when will it come? Tom Anderson <twic@urchin.earth.li> - 2011-08-09 22:38 +0100
        Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-10 00:36 +0200
          Re: setSize ArrayList, when will it come? Roedy Green <see_website@mindprod.com.invalid> - 2011-08-09 15:55 -0700
          Re: setSize ArrayList, when will it come? Knute Johnson <september@knutejohnson.com> - 2011-08-09 16:03 -0700
            Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-10 09:18 +0200
              Re: setSize ArrayList, when will it come? Mayeul <mayeul.marguet@free.fr> - 2011-08-10 11:26 +0200
                Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-10 12:35 +0200
              Re: setSize ArrayList, when will it come? Lew <lewbloch@gmail.com> - 2011-08-10 09:33 -0700
                Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-10 20:22 +0200
          Re: setSize ArrayList, when will it come? Patricia Shanahan <pats@acm.org> - 2011-08-09 22:13 -0700
            Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-11 02:01 +0200
              Re: setSize ArrayList, when will it come? Patricia Shanahan <pats@acm.org> - 2011-08-10 18:42 -0700
                Re: setSize ArrayList, when will it come? Jan Burse <janburse@fastmail.fm> - 2011-08-11 14:21 +0200
    Re: setSize ArrayList, when will it come? Arne Vajhøj <arne@vajhoej.dk> - 2011-08-09 20:09 -0400
  Re: setSize ArrayList, when will it come? Roedy Green <see_website@mindprod.com.invalid> - 2011-08-09 16:02 -0700
    Re: setSize ArrayList, when will it come? Arne Vajhøj <arne@vajhoej.dk> - 2011-08-09 20:13 -0400

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