On Fri, 20 Jun 2025 15:52:08 GMT, Roger Riggs <rri...@openjdk.org> wrote:
>> My suggestion is to call `new StringBuilder(0)` as it is possible this is >> completely unused because we always hit the `eol && sb.length() == 0` path >> below. > > The change is motivated by performance, but there will be many inputs that > are less than the transfer buffer size and those will not use the > StringBuilder, so creating it before it is needed could be avoided. > When a partial line is left in the transfer buffer, copy it to the beginning > of the buffer and read more characters for the remaining size of the buffer. > It would save some copying into and out of the SB. > You might still need a fallback for really long lines (> transfer buffer > size), but that might be more easily handled by reallocating the transfer > buffer to make it larger. resizing/newCapacity is always expensive and tricky, string builder included. so maybe we should decide if 'long lines' (> transfer buffer size) is the goal of this pr. if not, it might be reasonable/make sense (???) to simply go with "string" +its the built-in string concatenation. i do agree we probably want to avoid paying the cost of copying in & out of the sb, but tweaking the transfer buffer resizing might also be tricky and potentially out of the scope as well. yes, it's always a trade off. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/25863#discussion_r2159408170
