RFR: 8356709: Avoid redundant String formatting in BigDecimal.valueOf(double)

[Johannes Graham]

On Sun, 11 May 2025 18:45:47 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Optimize `BigDecimal.valueOf(double)` by using `FormattedFPDecimal` instead of converting to decimal string and then parsing it. This results in an approximate 6x improvement for me.
>
> test/jdk/java/math/BigDecimal/ValueOfDouble.java line 14:
> 
>> 12: 
>> 13: public class ValueOfDouble {
>> 14:     private static final String DIGITS = "1234567899123456789"; // Enough digits to fill a long
> 
> Should we consider including 0 in this list?
> 
> This file needs a license header, and the jtreg directive should be `/*` instead of `/**` and usually placed before imports, and usually we include a `@bug` tag (once there is an issue ID) and a `@summary` tag.

I left out 0 specifically to ensure the all  precisions  were tried. The loop over the exponents effectively adds zeros afterwards.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25173#discussion_r2083600670