RFR: 8298033: Character.codePointAt(char[], int, int) doesn't do JavaDoc-specified check [v3]

[Roger Riggs]

On Mon, 5 Dec 2022 13:22:36 GMT, Sergey Tsypanov <stsypanov at openjdk.org> wrote:

>> Yeah, this AIOOBE is exactly the reason why I added this. So should we modify `codePointBefore` in the same way as `codePointAt`?
>
> I'm asking because counter-intuitively `codePointBefore ` doesn't specify IOOBE for negative `index`.
> 
> /**
>  * @return the Unicode code point value before the given index.
>  * @throws NullPointerException if {@code a} is null.
>  * @throws IndexOutOfBoundsException if the {@code index}
>  * argument is not greater than the {@code start} argument or
>  * is greater than the length of the {@code char} array, or
>  * if the {@code start} argument is negative or not less than
>  * the length of the {@code char} array.
>  * @since  1.5
>  */
>  ```

The corresponding test case for `codePointBefore` is:

        callCodePoint(Before, a, a.length+1, a.length-1, IndexOutOfBoundsException.class);

The implementation is checking that `start` does not exceed the length but it should be checking that `index` does not exceed the length.

Since `start` must be non-negative and `index` must be greater than `start, it follows that `index` must non-negative and then checked against the length.

-------------

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