RFR: 8351443: Improve robustness of StringBuilder [v9]

[Markus KARG]

On Fri, 9 May 2025 16:41:39 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> Refactor AbstractStringBuilder to maintain consistency among count, coder, and value buffers while the buffer capacity is being expanded and/or inflated from Latin1 to UTF16 representations. 
>> The refactoring pattern is to read and write AbstractStringBuilder fields once using locals for all intermediate values. 
>> Support methods are static, designed to pass all values as arguments and return a value.
>> 
>> The value byte array is reallocated under 3 conditions:
>> - Increasing the capacity with the same encoder
>> - Increasing the capacity and inflation to change the coder from LATIN1 to UTF16
>> - Inflation with the same capacity
>> 
>> Added StressSBTest to exercise public instance methods of StringBuilder.
>
> Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Removed extraneous "the"

src/java.base/share/classes/java/lang/StringUTF16.java line 1535:

> 1533:         checkBoundsBeginEnd(i, end, value);
> 1534:         putChar(value, i, c1);
> 1535:         putChar(value, i + 1, c2);

Can someone please shed some light on this change: What is the benefit of `i + constant` over `i++`? 🤔

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PR Review Comment: https://git.openjdk.org/jdk/pull/24967#discussion_r2094144854