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Groups > comp.lang.java.programmer > #26234

Re: StringBuilder.append and CharSequence

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Arne Vajhøj <arne@vajhoej.dk> wrote:
> On 9/27/2013 8:52 AM, Andreas Leitgeb wrote:
>> If a CharSequence is a vehicle to transport the char and the number
>> into StringBuilder's reach, then this is some big boilerplate substitute
>> for the sorely missing .append(int num, char ch) method, but not goofy.
>>
>> If this CharSequence was then merely used to create a big dull
>> temp object via toString(), then it goes right back to "goofy".
> I would not worry about temporary object being created
> unless I observe an actual problem.

I had considered this thread done already, but since there is further
interest...

There's really two aspects to my original problem.
 1) will any temporary object be created when append()ing a CharSequence
      to a StringBuilder?
 2) might StringBuilder eventually call a CharSequence's toString() from
      within it's .append()?

A positive answer for 2) would also imply "yes" for 1), of course.
Given the *current* implementation of Oracle's implementation,
  the answer to both questions is (fortunately) negative.
Even the consequences of a "1) yes 2) no" reply would not really be
  as "earth-shattering" as I might have implied so far in this thread.

Now, for question 2)

There'll be essentially two kinds of CharSequence implementations:
 a) some kind of "mutable String-alike", like e.g. StringBuilder.
      these likely save their data in some char[] already, and 
      creating a String of that is trivial.
 b) those that "calculate" each char in charAt().
      My ChSeq falls into that category, and maybe a couple other
      special purpose ones.

For those of kind b), being allowed to slam "this" to a StringBuilder
and then have the StringBuilder create a String object, would sound like
a nice example of code-reuse, compared to having to write the loop and
append-call for each char.

I don't really have any idea, how many CharSequence implementations
of kind b) really exist in the world, and it is not unlikely, that
they are far too few to justify any thought at all, but nevertheless,
I wish that StringBuilder.append() were SPECIFIED to use CharSequence-
API (i.e. essentially length() and charAt(), as is already implemented)
to SAFELY allow for trivial .toString() implementations in those classes.

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Thread

StringBuilder.append and CharSequence Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-09-25 14:19 +0000
  Re: StringBuilder.append and CharSequence markspace <markspace@nospam.nospam> - 2013-09-25 13:02 -0700
    Re: StringBuilder.append and CharSequence markspace <markspace@nospam.nospam> - 2013-09-25 18:34 -0700
      Re: StringBuilder.append and CharSequence Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-09-26 17:37 +0000
        Re: StringBuilder.append and CharSequence Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2013-09-26 23:11 +0200
          Re: StringBuilder.append and CharSequence Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-09-27 13:30 +0000
            Re: StringBuilder.append and CharSequence Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2013-09-27 19:31 +0200
              Re: StringBuilder.append and CharSequence markspace <markspace@nospam.nospam> - 2013-09-27 13:45 -0700
                Re: StringBuilder.append and CharSequence Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-09-27 23:16 +0000
                Re: StringBuilder.append and CharSequence Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> - 2013-09-29 04:58 +0200
                Re: StringBuilder.append and CharSequence Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-09-30 20:02 +0000
  Re: StringBuilder.append and CharSequence Arne Vajhøj <arne@vajhoej.dk> - 2013-09-25 20:57 -0400
    Re: StringBuilder.append and CharSequence Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-09-26 18:01 +0000
      Re: StringBuilder.append and CharSequence Arne Vajhøj <arne@vajhoej.dk> - 2013-09-26 15:47 -0400
        Re: StringBuilder.append and CharSequence Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-09-26 20:48 +0000
          Re: StringBuilder.append and CharSequence Arne Vajhøj <arne@vajhoej.dk> - 2013-09-26 16:58 -0400
            Re: StringBuilder.append and CharSequence Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-09-27 12:52 +0000
              Re: StringBuilder.append and CharSequence Arne Vajhøj <arne@vajhoej.dk> - 2013-10-04 20:59 -0400
                Re: StringBuilder.append and CharSequence Andreas Leitgeb <avl@gamma.logic.tuwien.ac.at> - 2013-10-05 12:51 +0000
  Re: StringBuilder.append and CharSequence Sven Köhler <remove-sven.koehler@gmail.com> - 2013-09-27 15:41 +0300

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