Path: csiph.com!x330-a1.tempe.blueboxinc.net!newsfeed.hal-mli.net!feeder3.hal-mli.net!newsfeed.hal-mli.net!feeder1.hal-mli.net!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, 28 Jun 2011 14:34:22 -0500
Date: Tue, 28 Jun 2011 12:34:15 -0700
From: Patricia Shanahan <pats@acm.org>
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.17) Gecko/20110414 Thunderbird/3.1.10
MIME-Version: 1.0
Newsgroups: comp.lang.java.programmer
Subject: Re: Why "lock" functionality is introduced for all the objects?
References: <d0bb9e06-16f0-4282-a37e-47e9ca9630ec@r2g2000vbj.googlegroups.com> <iuce66$2nh$1@news.albasani.net> <iud083$2jr$1@news.onet.pl> <iud1u5$f4r$1@news.albasani.net> <iud4f6$lcm$1@news.onet.pl> <iud5js$nno$1@news.albasani.net> <iud66f$8al$1@speranza.aioe.org> <J5KdnRBP4eYkvZfTnZ2dnUVZ_jqdnZ2d@earthlink.com> <iud80u$ci0$2@speranza.aioe.org>
In-Reply-To: <iud80u$ci0$2@speranza.aioe.org>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Message-ID: <rYCdnRgQGaQjsZfTnZ2dnUVZ_hydnZ2d@earthlink.com>
Lines: 30
X-Usenet-Provider: http://www.giganews.com
NNTP-Posting-Host: 70.230.196.78
X-Trace: sv3-n6Iu0KKY/p8EFuNA3ARJyNbWCYUS1KH/oiBe+Eoj9Ng7Ba4r1hTTQ7IHA9QH04awRa4c6By2/bHfmhj!LcmlGoCGiaNFShJigt0d9Ais0nBMXIMvmBVxKc6pDsHgwdNDzvuvG5iD/3zSuahTB9deWL/9OTvn!q07yymexIs/c3lXfHQs5ciT/2e1xtRFuhkWBypB0S5pfOA==
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: 2738
Xref: x330-a1.tempe.blueboxinc.net comp.lang.java.programmer:5748

On 6/28/2011 11:54 AM, 
supercalifragilisticexpialadiamaticonormalizeringelimatisticantations wrote:
> On 28/06/2011 2:42 PM, Patricia Shanahan wrote:
>> Each String instance has the following fields:
>>
>> private final char value[];
>> private final int offset;
>> private final int count;
>> private int hash;
>>
>> There are 12 bytes in addition to the char array. The offset and count
>> fields allow quick sub-string construction, and hash is used to cache
>> the hashCode result.
>
> Oh, geez, even *more* overhead. And let's not forget the array has its
> own separate object header and length field!

The array may be shared by several String objects.

In general, many trade-offs in Java, not just the decision to make every
object capable of being a lock, assume that other considerations are
more important than minimizing memory use. For example, caching the hash
code pays four bytes per String in order to have a hash code that
depends on the entire string, without paying the cost of calculating it
repeatedly when a String is used as a hash table key.

If, for your purposes, minimal memory use is very important, you may
want to consider other languages with other trade-offs.

Patricia