RFR: 8316426: Optimization for HexFormat.formatHex

[Roger Riggs]

On Fri, 15 Sep 2023 22:19:53 GMT, 温绍锦 <duke at openjdk.org> wrote:

> HexDecimal#DIGITS is a table with a size of 512 bytes. I think that in such a table, when it needs to be used continuously, it is worthwhile to perform table lookup operations.

HexFormat was designed for presenting bytes to humans, typical line lengths for the useful output are 80-130 characters, so input sizes of 40-65 bytes, probably less when other interpretations (such as latin1 or ascii) are appended.
And the output is not typically performance sensitive. Please keep the code small and easy to maintain.

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PR Comment: https://git.openjdk.org/jdk/pull/15768#issuecomment-1724036912