RFR: 8361300: Document exceptions for Unsafe offset methods [v4]

[ExE Boss]

On Thu, 3 Jul 2025 18:41:27 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Unsafe throws IAE for misusing static vs instance fields, and it's revealed that AtomicXxxFieldUpdaters are using this mechanism to reject static fields. This is not a good practice, but we can at least document this so we don't accidentally introduce problems.
>
> Chen Liang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Test to verify observed internal unsafe behaviors

test/jdk/jdk/internal/misc/Unsafe/AddressComputationContractTest.java line 91:

> 89:         assertDoesNotThrow(() -> getUnsafe().arrayBaseOffset(int[].class));
> 90:         assertThrows(NullPointerException.class, () -> getUnsafe().arrayBaseOffset(null));
> 91:         // Caused by VM trying to throw java.lang.InvalidClassException (there's one in java.io instead)

Note that the one in `java.io` is also a checked exception (extends `java.io.ObjectStreamException` which extends `java.io.IOException`).

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PR Review Comment: https://git.openjdk.org/jdk/pull/25945#discussion_r2188513237