RFR: 8352171: Arrays.hashCode for sub-range of byte array API addition

[Roger Riggs]

On Thu, 20 Mar 2025 21:50:59 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Add the java.util.Arrays.hashCode(byte[], int start, int end).
>> 
>> Hi team, I am new here, please give me some guidance. Thank you.
>
> src/java.base/share/classes/java/util/Arrays.java line 4454:
> 
>> 4452:      */
>> 4453:     public static int hashCode(byte[] a, int fromIndex, int toIndex) {
>> 4454:         if (a == null) {
> 
> The `a == null` special check is dubious - `a == null` has a meaning if we are hashing a whole `byte[]` object, but with a specific `fromIndex` and `toIndex` it just doesn't work.
> 
> That said, we might consider accepting the initial hash too - For example, we have two `byte[]` arrays and we want a concatenated hash. The initial hash allows us to compute such a hash from two arrays easily.

None of the other public APIs for hashcode include an initial value argument. 
The caller can easily combine the hashcode values themselves as needed.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24128#discussion_r2018886224