RFR: JDK-8329557: Fix statement around MathContext.DECIMAL128 rounding

[Joe Darcy]

On Wed, 3 Apr 2024 14:55:07 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> Happened to notice a semantic typo in the description of MathContext.DECIMAL128, use of "decimal64" where "decimal128" was intended, and added some additional information to make the related descriptions more informative.
>
> src/java.base/share/classes/java/math/MathContext.java line 106:
> 
>> 104:      * rounding mode of {@link RoundingMode#HALF_EVEN HALF_EVEN}.
>> 105:      * Note the exponent range of decimal128 (min exponent of -6143,
>> 106:      * max exponent of 6144) is <em>not</em> used for rounding.
> 
> The exponent ranges are all correct, but... why mention them in the first place if they are not used?

My thinking was to mention the ranges to show how different than are from the approx. +/- MAX_INT range of BigDecimal.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18587#discussion_r1549980224