Groups > comp.lang.java.programmer > #8110

Re: StringBuilder

From	Roedy Green <see_website@mindprod.com.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: StringBuilder
Date	2011-09-17 15:34 -0700
Organization	Canadian Mind Products
Message-ID	<vp7a77lp3e5oe4h79pnmv95vb4lu13spmc@4ax.com> (permalink)
References	<96f358c8-a024-40db-b60b-300186c2f813@o10g2000vby.googlegroups.com> <j41fik$3qb$1@news.albasani.net> <j52jgd$iij$1@dont-email.me>

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On Sat, 17 Sep 2011 19:56:50 +0300, Stanimir Stamenkov
<s7an10@netscape.net> wrote, quoted or indirectly quoted someone who
said :

>The StringBuilder.toString() is really fast - that's the point, and 
>I don't think it is worth mentioning it.

The places where StringBuilder wastes CPU cycles is when you have a
bad estimate and it has to create new buffer and copy what it has done
so far to it. If estimate is two low, you can get repeated such
doublings.  If it is too high, you fill up RAM too quickly and force
premature c.

My solution was FastCat which is quite easy to get a bang on estimate.
see http://mindprod.com/products1.html#FASTCAT

StringBuilder composes its string in a char[].  Unfortunately it can't
simply plop that into a String object at the end.  It has to allocate
yet another buffer, copy into it, and that becomes your string object.
The JVM is worried there might be encumbrances (pointers to) the
char[].  So it has to copy rather than reference.  Perhaps a little
native code could bypass the final copy.
-- 
Roedy Green Canadian Mind Products
http://mindprod.com
Your top priority should be fixing bugs. If you carry on development, 
you are just creating more places you will have to search for them.

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Re: StringBuilder Stanimir Stamenkov <s7an10@netscape.net> - 2011-09-17 19:56 +0300
  Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-17 20:35 +0200
  Re: StringBuilder Roedy Green <see_website@mindprod.com.invalid> - 2011-09-17 15:34 -0700
    Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-18 01:33 +0200
      Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-18 01:56 +0200
      Re: StringBuilder Roedy Green <see_website@mindprod.com.invalid> - 2011-09-17 20:58 -0700
    Re: StringBuilder Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-09-17 22:44 -0700
      Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-18 09:54 +0200
        Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-18 09:59 +0200
        Re: StringBuilder Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-09-18 07:28 -0700
      Re: StringBuilder Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-09-18 08:15 -0400
        Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-18 15:32 +0200
          Re: StringBuilder Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-09-18 09:50 -0400
            Re: StringBuilder Stanimir Stamenkov <s7an10@netscape.net> - 2011-09-18 17:08 +0300
            Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-18 22:13 +0200
              Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-18 22:29 +0200
                Re: StringBuilder Jan Burse <janburse@fastmail.fm> - 2011-09-18 22:39 +0200
      Re: StringBuilder Roedy Green <see_website@mindprod.com.invalid> - 2011-09-19 09:45 -0700

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