Path: csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!news.albasani.net!newsreader4.netcologne.de!news.netcologne.de!nx02.iad01.newshosting.com!newshosting.com!69.16.185.11.MISMATCH!npeer01.iad.highwinds-media.com!news.highwinds-media.com!feed-me.highwinds-media.com!border3.nntp.dca.giganews.com!Xl.tags.giganews.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local2.nntp.dca.giganews.com!nntp.earthlink.com!news.earthlink.com.POSTED!not-for-mail
NNTP-Posting-Date: Tue, 09 Aug 2011 06:00:44 -0500
Date: Tue, 09 Aug 2011 04:00:44 -0700
From: Patricia Shanahan <pats@acm.org>
User-Agent: Mozilla/5.0 (Windows NT 5.2; WOW64; rv:5.0) Gecko/20110624 Thunderbird/5.0
MIME-Version: 1.0
Newsgroups: comp.lang.java.programmer
Subject: Re: setSize ArrayList, when will it come?
References: <j1pp1j$3rf$1@news.albasani.net> <j1q1cv$aos$1@dont-email.me> <j1q596$gs8$1@news.albasani.net> <wcqdnZuEIsJJbd3TnZ2dnUVZ_hmdnZ2d@earthlink.com> <j1qtu4$iuj$1@news.albasani.net>
In-Reply-To: <j1qtu4$iuj$1@news.albasani.net>
Content-Type: text/plain; charset=ISO-8859-15; format=flowed
Content-Transfer-Encoding: 7bit
Message-ID: <K6CdnUGfCpfBjtzTnZ2dnUVZ_g6dnZ2d@earthlink.com>
Lines: 47
X-Usenet-Provider: http://www.giganews.com
NNTP-Posting-Host: 70.230.203.65
X-Trace: sv3-B15byrlPsUVk9crsl+//sg9SwzULrKRyZzUPsEUdh7SxhQWfElkQxti1ShtXFxYzXb4NS5HJPCxyiZP!k6JI7Upn+esIoDy8UkKRC4/G5RbLuMGmYjeAZU9Pt4SWQ8aSm+ICHaYK3bx2jtFHEVdTx+uTAk+q!EsKsrgD26zj4dk0lEBjFum5dp6InGp/59Fw5dVWghjMLVg==
X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly
X-Postfilter: 1.3.40
X-Original-Bytes: 2850
Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.programmer:6909

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