RFR: 8132995: Matcher$ImmutableMatchResult should be optimized to reduce space usage [v2]

[Stuart Marks]

On Thu, 11 May 2023 09:22:44 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> When appropriate and useful, copies only the relevant portion of the `CharSequence` to the match result.
>
> Raffaello Giulietti has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Added some randomness in tests.

src/java.base/share/classes/java/util/regex/Matcher.java line 271:

> 269:         return text instanceof String s ? s : text.subSequence(first, last).toString();
> 270:     }
> 271: 

I'd think we'd want to get a subSequence of any text, regardless of whether it's a String or some other CharSequence. This could result in a savings if there is a match result (or several match results) from find() operation(s) on a large String, when the matched text is relative small.

I'd also merge this into the creation of the MatchResult. The offset needs to be stored because the start/end locations are indexes into the original text, but we're storing only a subSequence of the original text. However, if we always store a subSequence, the offset is always the same as `first`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13231#discussion_r1195953652