On Tue, 21 Oct 2025 01:28:50 GMT, Shaojin Wen <[email protected]> wrote:

>> This PR refactors the Double.toHexString method to improve its performance 
>> by eliminating the use of StringBuilder and regex operations. The new 
>> implementation uses a direct byte array approach to construct the hex string 
>> representation, which avoids the overhead of StringBuilder operations and 
>> regex pattern matching.
>> 
>> Existing tests in `java/lang/Double/ToHexString.java`.
>
> Shaojin Wen has updated the pull request incrementally with one additional 
> commit since the last revision:
> 
>   fix test comment

src/java.base/share/classes/java/lang/Double.java line 725:

> 723:         // so that the string representation has a known length.
> 724:         // This ensures we always have 13 hex digits to work with (52 
> bits / 4 bits per hex digit)
> 725:         long signifBits = Double.doubleToLongBits(d) & 
> DoubleConsts.SIGNIF_BIT_MASK;

I think it would be clearer if the results of Double.doubleToLongBits(d) were 
stashed in a variable as this method is also called for the computation of the 
negative predicate.

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PR Review Comment: https://git.openjdk.org/jdk/pull/27811#discussion_r2446621869

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