RFR: 8327791: Optimization for new BigDecimal(String) [v12]

[Shaojin Wen]

On Wed, 13 Mar 2024 13:11:48 GMT, Shaojin Wen <duke at openjdk.org> wrote:

>> src/java.base/share/classes/java/math/BigDecimal.java line 596:
>> 
>>> 594:                 // First compact case, we need not to preserve the character
>>> 595:                 // and we can just compute the value in place.
>>> 596:                 for (; ; c = val.charAt(++offset)) {
>> 
>> This looks gnarly, and it's unclear if it's correct for invalid inputs like `""`, `"-"` and `"+"` since you're not testing for `len > 0` before going into the loop. Can you make sure there are tests covering such inputs and try to simplify this?
>
> If the input is "+" or "-" an exception will be thrown on line 583
> 
>             boolean isneg = c == '-'; // leading minus means negative
>             if (isneg || c == '+') {
>                 c = val.charAt(++offset); 
>                 len--;
>             }

if the input is "" an exception will be throw on line 579

            int offset = 0;
            char c = val.charAt(offset);

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PR Review Comment: https://git.openjdk.org/jdk/pull/18177#discussion_r1523237018