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Groups > comp.lang.java.programmer > #25363

Re: StringBuilder.append and CharSequence

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Arne Vajhøj <arne@vajhoej.dk> wrote:
> On 9/26/2013 2:01 PM, Andreas Leitgeb wrote:
>> Arne Vajhøj <arne@vajhoej.dk> wrote:
>>> On 9/25/2013 10:19 AM, Andreas Leitgeb wrote:
>>>> Is it safe to use "stringBuilder.append(this);" in a CharSequence
>>>> implementation's .toString(), or could this lead to a recursive
>>>> loop, if some version of a Java class library implements the
>>>> append() for CharSequence by using it's toString() ?
>>> <quote>
>>> The principal operations on a StringBuilder are the append and insert
>>> methods, which are overloaded so as to accept data of any type. Each
>>> effectively converts a given datum to a string and then appends or
>>> inserts the characters of that string to the string builder.
>>> </quote>
>>>
>>> Based on the use of "string" and "and then" I interpret this as:
>>> <interpretation>
>>> Append has two distinct sequential phases:
>>> 1) convert the argument to an instance of java.util.String

I only noticed this now:  "java.util.String" - is that a typo for
java.lang.String, or is there really a (non-public) java.util.String?

>>> 2) append that to the StringBuilder
>>> </interpretation>
>>
>> If .append() used .toString(), then there wouldn't be a point for offering
>> a CharSequence overload. It could then just offer one overload for Object
>> (apart from those for primitive types), and be set.
> Yes. But "convert the argument to an instance of java.util.String" is
> not the same as calling .toString()

append() might create a snapshot-copy of the CharSequence, and it doesn't
matter if that is in some extra non-public class, a simple char[] or the
well-known java.lang.String.  What *does* matter (at least to me, who
started this thread) is, whether it uses Object.toString() or the specific
CharSequence methods to obtain that snapshot.

Although the docs aren't explicit on this, they now appear to imply it
well enough for me to firmly believe the latter.

Mostly, because the docs for append(Object) *are* explicit about using
String.valueOf(obj) (and thus indirectly toString(), unless null)

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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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