Groups > comp.lang.java.programmer > #5829

Re: StringBuilder Difficulties

From	lewbloch <lewbloch@gmail.com>
Newsgroups	comp.lang.java.programmer
Subject	Re: StringBuilder Difficulties
Date	2011-07-03 00:08 -0700
Organization	http://groups.google.com
Message-ID	<7c5d329e-6db5-4b52-8501-b9ae9c3a8738@k23g2000pri.googlegroups.com> (permalink)
References	<c4tk07dv1pq7u8k32qd6b7o1brc2rj8r30@4ax.com> <971fj1Fg1rU1@mid.individual.net> <irln07dveti624e71v8viderf0hjtudue5@4ax.com>

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Gene Wirchenko wrote:
> blm...@myrealbox.com wrote
>> up a string piece by piece.  You *could* write something like
>>
>> String a = "first";
>> a += " second";
>> a += " etc";
>>
>> and my *guess* is that this is not horribly inefficient if the
>> number of concatenation operations is small.  (The conventional
>

>      IOW, who cares if it is only a bit of inefficiency?  Agreed.
>

>> wisdom, as I understand it, is that the Java runtime is pretty
>> good at managing short-lived objects, so creating new objects is
>> not invariably something to avoid, though as with anything else
>> one shouldn't get carried away, maybe.  Again the experts may
>> disagree.)
>>
>> But if there are a lot of concatenation operations it's said to be
>> more efficient to use a StringBuilder, e.g.:
>>
>> StringBuilder sb = new StringBuilder();
>> sb.append("first");
>> sb.append(" second");
>> sb.append(" etc");
>> String a = sb.toString();
>

>      It is.  My test code appends one character at a time. Switching
> from String to StringBuilder cut the execution time by about 40%.
>

>> The above is what I mostly use StringBuilder for; there are
>> undoubtedly other things one can do with it as well, some of
>> which may be useful to you (I haven't followed carefully all the
>> threads you've started).
>>

Lines like:

   String thing = getResult() + " found by " + foundSource() +".";

get optimized under the hood, so use of something like 'StringBuilder'
on such one-liners is useless.  The usefulness kicks in with the sort
of idiom blmblm described - multi-line expressions in loops where the
compiler builds lots of 'String' instances and can't figure out to use
'StringBuilder' by itself.

The efficiency doesn't come from the re-use of the 'StringBuilder'
object from iteration to iteration.  The create/destroy mechanism for
short-lived objects favors creating the temporary object inside the
loop, not outside.  The efficiency comes from not having to create so
many superfluous 'String' objects.

--
Lew

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StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-06-28 17:54 -0700
  Re: StringBuilder Difficulties Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-28 21:29 -0400
    Re: StringBuilder Difficulties Lew <noone@lewscanon.com> - 2011-06-29 00:48 -0400
      Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-06-29 12:19 -0700
    Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-06-29 12:11 -0700
      Re: StringBuilder Difficulties Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-29 22:06 -0400
  Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-29 20:17 +0000
    Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-06-29 18:55 -0700
      Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-06-30 20:30 +0000
        Re: StringBuilder Difficulties Patricia Shanahan <pats@acm.org> - 2011-06-30 14:17 -0700
          Re: StringBuilder Difficulties Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-30 21:36 -0400
            Re: StringBuilder Difficulties "John B. Matthews" <nospam@nospam.invalid> - 2011-07-01 01:41 -0400
        Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-06-30 14:26 -0700
          Re: StringBuilder Difficulties Steve Sobol <sjsobol@JustThe.net> - 2011-06-30 17:33 -0700
          Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-01 20:47 +0000
            Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-01 17:29 -0700
              Re: StringBuilder Difficulties rossum <rossum48@coldmail.com> - 2011-07-02 11:36 +0100
              Re: StringBuilder Difficulties Robert Klemme <shortcutter@googlemail.com> - 2011-07-02 12:58 +0200
                Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-04 07:52 -0700
                Re: StringBuilder Difficulties Robert Klemme <shortcutter@googlemail.com> - 2011-07-04 21:45 +0200
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-05 02:06 -0400
                Re: StringBuilder Difficulties markspace <-@.> - 2011-07-05 09:32 -0700
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-05 14:13 -0400
                Re: StringBuilder Difficulties markspace <-@.> - 2011-07-05 12:51 -0700
                Re: StringBuilder Difficulties Silvio <silvio@moc.com> - 2011-07-05 23:16 +0200
                Re: StringBuilder Difficulties markspace <-@.> - 2011-07-05 15:08 -0700
                Re: StringBuilder Difficulties Silvio <silvio@moc.com> - 2011-07-06 09:41 +0200
                Re: StringBuilder Difficulties "eye" <eye@mocka.com> - 2011-07-06 09:55 +0000
                Re: StringBuilder Difficulties thoolen <thoolen@tholenbot.thorium> - 2011-07-06 05:37 -0400
                Re: StringBuilder Difficulties "thoolen" <thoolen@tholenbot.thorium> - 2011-07-06 08:43 -0400
                Re: StringBuilder Difficulties thoolen <thoolen@tholenbot.thorium> - 2011-07-06 22:30 -0400
                Re: StringBuilder Difficulties "Stefan Robacki" <noemail@noemail.foobar> - 2011-07-06 00:04 -0400
                Re: StringBuilder Difficulties thoolen <thoolen@tholenbot.thorium> - 2011-07-06 05:45 -0400
                Re: StringBuilder Difficulties thoolen <thoolen@tholenbot.thorium> - 2011-07-06 08:26 -0400
                Re: StringBuilder Difficulties thoolen <thoolen@tholenbot.thorium> - 2011-07-06 22:36 -0400
                Re: StringBuilder Difficulties "tholen@antispam.ham" <tholen@ifa.hawaii.edu> - 2011-07-06 06:09 -0700
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 22:40 -0400
                Re: StringBuilder Difficulties John Doe <jdoe@usenetlove.invalid> - 2011-07-14 06:50 +0000
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-14 02:58 -0400
                Re: StringBuilder Difficulties Jane Doe <jdoe@love.in.d.jungle.invalid> - 2011-07-14 10:20 -0400
                Re: StringBuilder Difficulties thoolen <tholen01@gmail.com> - 2011-07-14 07:33 -0700
                Re: StringBuilder Difficulties Stanimir Stamenkov <s7an10@netscape.net> - 2011-07-05 23:44 +0300
                Re: StringBuilder Difficulties markspace <-@.> - 2011-07-05 14:08 -0700
              Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-02 18:33 +0000
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-02 16:56 -0400
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-03 01:34 +0000
                Re: StringBuilder Difficulties Patricia Shanahan <pats@acm.org> - 2011-07-02 19:55 -0700
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-04 03:32 +0000
                Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-04 08:04 -0700
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-05 19:12 +0000
                Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-05 14:06 -0700
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-05 21:16 +0000
                Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-05 17:29 -0700
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-06 16:59 +0000
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 19:52 -0400
                Re: StringBuilder Difficulties Patricia Shanahan <pats@acm.org> - 2011-07-06 16:58 -0700
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 19:52 -0400
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 21:54 -0400
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 22:18 -0400
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 22:41 -0400
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-08 17:45 +0000
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 05:48 -0400
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-06 16:59 +0000
                Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-06 10:56 -0700
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-08 17:44 +0000
                Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-08 11:51 -0700
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-10 19:08 +0000
                Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-11 07:54 -0700
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-11 22:37 +0000
                Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-11 15:52 -0700
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 08:25 -0400
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 19:41 -0400
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 19:58 -0400
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 21:57 -0400
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 22:17 -0400
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 22:44 -0400
                Re: StringBuilder Difficulties Steve Erwin <trollHunter@Usenet.4.usenetizens.org.invalid> - 2011-07-07 12:51 +1000
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-06 23:02 -0400
                Re: StringBuilder Difficulties John Doe <jdoe@usenetlove.invalid> - 2011-07-14 06:32 +0000
                Re: StringBuilder Difficulties supercalifragilisticexpialadiamaticonormalizeringelimatisticantations <supercalifragilisticexpialadiamaticonormalizeringelimatisticantations@averylongandannoyingdomainname.com> - 2011-07-14 02:57 -0400
                Re: StringBuilder Difficulties Jane Doe <jdoe@love.in.d.jungle.invalid> - 2011-07-14 10:07 -0400
                Re: StringBuilder Difficulties thoolen <tholen01@gmail.com> - 2011-07-14 07:24 -0700
                Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-04 07:58 -0700
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-05 19:09 +0000
                Re: StringBuilder Difficulties KitKat <kitkat_11697@gmail.example.com> - 2011-07-05 15:15 -0400
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-05 20:03 +0000
                Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-07-05 14:11 -0700
                Re: StringBuilder Difficulties blmblm@myrealbox.com <blmblm.myrealbox@gmail.com> - 2011-07-06 16:55 +0000
      Re: StringBuilder Difficulties lewbloch <lewbloch@gmail.com> - 2011-07-03 00:08 -0700
        Re: StringBuilder Difficulties Robert Klemme <shortcutter@googlemail.com> - 2011-07-03 12:35 +0200
          Re: StringBuilder Difficulties lewbloch <lewbloch@gmail.com> - 2011-07-04 04:07 -0700
  Re: StringBuilder Difficulties Patricia Shanahan <pats@acm.org> - 2011-06-29 14:38 -0700
    Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-06-29 15:00 -0700
      Re: StringBuilder Difficulties Patricia Shanahan <pats@acm.org> - 2011-06-29 15:52 -0700
        Re: StringBuilder Difficulties Gene Wirchenko <genew@ocis.net> - 2011-06-29 18:58 -0700
          Re: StringBuilder Difficulties Patricia Shanahan <pats@acm.org> - 2011-06-29 19:26 -0700
          Re: StringBuilder Difficulties lewbloch <lewbloch@gmail.com> - 2011-07-03 00:11 -0700
  Re: StringBuilder Difficulties Roedy Green <see_website@mindprod.com.invalid> - 2011-06-29 18:32 -0700

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