On Tue, 8 Oct 2024 12:08:06 GMT, Markus KARG <d...@openjdk.org> wrote:
>> src/java.base/share/classes/java/io/Reader.java line 174:
>>
>>> 172:
>>> 173: return new Reader() {
>>> 174: private final int length = cs.length();
>>
>> Hello Markus, as far as I can see, a `CharSequence` is allowed to have a
>> non-fixed `length()` (typically allowed to increase?). Is there a reason why
>> the length is captured at construction time instead of being evaluated
>> during the read operations of the `Reader`?
>
> As the anonymous class MUST NOT be used with multiple threads, I always have
> seen the `CharSequence` as *fixed/static* text in the moment the `Reader` is
> getting used. But indeed, technically one could interleave `Reader::read()`
> invocations by `CharSequence.append()` (or even worse,
> `CharSequence.delete()`) invocations. The question is: Would that make *any*
> sense in the end? I mean, what happens if one has `read()` text that in the
> next step gets `delete()`'d? I cannot image *any* scenario where such a
> program would result in *useful* outcome.
>
> <fun>The fact that nobody so far (before you) brought up this question
> seems to proof that nobody (besides you) would write such a program. 😄
> </fun>
>
> So I would plea for clearly saying in the JavaDocs that `cs` MUST NOT be
> modified before `close()` is called. Every other solution implies strange
> side effects and slower and error-prone implementation of both, anoynous
> reader *and* test.
>
> @AlanBateman WDYT?
I would treat this specific scenario as one of the "no concurrent usage"
examples. Note that by this principle, mutable objects like `StringBuilder`
should not override object comparison methods as these states can change, but
they do :(
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PR Review Comment: https://git.openjdk.org/jdk/pull/21371#discussion_r1791787167
