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Groups > comp.lang.java.programmer > #25385

Re: StringBuilder.append and CharSequence

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On 2013-09-28 01:16, Andreas Leitgeb allegedly wrote:
> markspace <markspace@nospam.nospam> wrote:
>> On 9/27/2013 10:31 AM, Daniele Futtorovic wrote:
>>> On 2013-09-27 15:30, Andreas Leitgeb allegedly wrote:
>>>> Daniele Futtorovic <da.futt.news@laposte-dot-net.invalid> wrote:
>>>>> I'd make the toString() as follows to be on the safe side:
>>>>>    char[] cs = new char[ m_len ];
>>>>>    Arrays.fill( cs, m_ch );
>>>>>    return new String(cs);
>>>> If this is the ONLY safe side, then there wouldn't be a point
>>>> in implementing a CharSequence in the first place for my task.
>>> Why not? The Standard API's StringBuilder#append(CharSequence), AFAICS,
>>> does not call toString() -- granted, the JavaDoc stipulates nothing to
>>> that effect.
>>
>> I read Andreas's comment as "there's not point introducing a new type if 
>> a repeated string is just always turned into a regular String anyway."
> 
> Yes, that's about it.
> 
> The "new type" is the ChSeq from a few posts upthread.
> The "repeated string" is a possibly long repetition of
> just a single char, compactly represented by ChSeq...
> 

Yes, but using the ChSeq (as it was introduced) to append it to a
StringBuilder WILL NOT, as the JSE currently stands, result in the
invocation of toString(). So you are safe to go.

Then, as far as the implementation of toString() is concerned (which
only matters if other API use your ChSeq's), I would say it ought to be
implemented as above, for safety reasons and because, after all, since
every String uses a char[] buffer, it stands to reason that you cannot
produce a String, which toString() is supposed to do, without allocating
such a buffer (as an optimisation, you could create it but once on demand).

Incidentally, while I know no place in the documentation that expresses
it, it is likely the case that all API designed to handle CharSequence's
will operate on a by-char-basis (as opposed to calling toString() ) if
they can afford it at all -- seeing how this is what the CharSequence
interface is all about.

-- 
DF.

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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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