RFR: 8358533: Improve performance of java.io.Reader.readAllLines

[Brian Burkhalter]

On Wed, 18 Jun 2025 00:53:51 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> Replaces the implementation `readAllCharsAsString().lines().toList()` with reading into a temporary `char` array which is then processed to detect line terminators and copy non-terminating characters into strings which are added to the list.
>
> src/java.base/share/classes/java/io/Reader.java line 469:
> 
>> 467:                     if (c == '\r' || c == '\n')
>> 468:                         break;
>> 469:                     term++;
> 
> It might be worth adding a test of unconventional sequences or \r and \n, including \r\r and \n\n, \r.
> The current ReadAll test cover the conventional sequences on Linux and Windows.

I agree. I was intending to follow up on @jaikiran's [comment](https://github.com/openjdk/jdk/pull/24728#discussion_r2112052404), probably in an update to this request.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25863#discussion_r2153448060