RFR: 8298033: Character.codePointAt(char[], int, int) doesn't do JavaDoc-specified check

[Brett Okken]

On Fri, 2 Dec 2022 12:44:18 GMT, Sergey Tsypanov <stsypanov at openjdk.org> wrote:

> I found out that this code
> 
> public class Main {
>     public static void main(String[] args) {
>         String s = "Hello world!";
>         char[] chars = s.toCharArray();
>         int point = Character.codePointAt(chars, -1, 1);
>     }
> }
> 
> throws `ArrayIndexOutOfBoundsException` instead of JavaDoc-specified `IndexOutOfBoundsException`: 
> 
> Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 12
> 	at java.base/java.lang.Character.codePointAtImpl(Character.java:9254)
> 	at java.base/java.lang.Character.codePointAt(Character.java:9249)
> 	at org.example.Main.main(Main.java:7)
> 
> and the method doesn't check whether `index` parameter is negative:
> 
> public static int codePointAt(char[] a, int index, int limit) {
>     if (index >= limit || limit < 0 || limit > a.length) {
>         throw new IndexOutOfBoundsException();
>     }
>     return codePointAtImpl(a, index, limit);
> }
> 
> I suggest to check the `index` parameter explicitly instead of relying on AIOOBE thrown from accessing the array with negative index.

As `ArrayIndexOutOfBoundsException` is an `IndexOutOfBoundsException`, it is not clear to me how this is not matching the javadoc/spec.
https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/ArrayIndexOutOfBoundsException.html

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PR: https://git.openjdk.org/jdk/pull/11480