RFR: 8317980: Optimization for Integer.parseInt and Long.parseLong

[Hannes Greule]

On Thu, 12 Oct 2023 00:39:27 GMT, David Schlosnagle <duke at openjdk.org> wrote:

>> He means to pull the `radix< Character,MIN_RADIX` and `radix > Character.MAX_RADIX` shared code in Integer and Long.parseInt (with radix version) to a helper method.
>
> More explicitly I was thinking something like below. 
> 
> I do wonder if some of the benchmark tests should cover the exceptional cases. I have seen many systems where attempting to try and parse potentially invalid inputs can hit expensive NumberFormatException fallbacks (though `-XX:+OmitStackTraceInFastThrow` may eventually kick in). [Guava offers `Integer Ints.tryParse(String)`](https://guava.dev/releases/32.1.3-jre/api/docs/com/google/common/primitives/Ints.html#tryParse(java.lang.String)) and similar to avoid the exception overhead at the cost of boxing for happy path of valid `int` and `null` for invalid.
> 
> 
>         checkCanParseLength(s);
>         checkCanParseRadix(radix);
>         int len = s.length();
> 
> 
>     private static void checkCanParseLength(String s) {
>         if (s == null) {
>             throw NumberFormatException.forNull();
>         }
> 
>         if (s.isEmpty()) { // would be interesting to see if this is equivalent to `s.length() == 0` for happy paths
>             throw NumberFormatException.forEmpty();
>         }
>     }
> 
>     private static void checkCanParseRadix(int radix) {
>         if (radix < Character.MIN_RADIX) {
>             throw NumberFormatException.forMinRadix(radix);
>         }
> 
>         if (radix > Character.MAX_RADIX) {
>             throw NumberFormatException.forMaxRadix(radix);
>         }
>     }

While only optimizing the fast path is a good idea, I think it is important to make sure there is no regression on the slow path - as @schlosna pointed out, it's a common way to check if a string can be converted to an int.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16112#discussion_r1356495786