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

[Shaojin Wen]

On Wed, 18 Jun 2025 00:04:37 GMT, Brian Burkhalter <bpb 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.

If we want better performance, we should go a step further and overload the readAllLines method in the Reader implementation class.

For example, in the most commonly used InputStreamReader, overload readAllLines through StreamDecoder and make special optimizations for UTF8/ISO_8859_1 encoding.

In StringReader, special overload methods can also be used for optimization.

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PR Comment: https://git.openjdk.org/jdk/pull/25863#issuecomment-2983379522