RFR: 8362637: Convert java.nio.ByteOrder to an enum

[Roger Riggs]

On Mon, 6 Oct 2025 18:21:26 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

> Convert java.nio.ByteOrder to an enum.
> The class declaration is changed from `public class` to `public enum`.
> Enums are `Comparable` so declare LITTLE_ENDIAN before BIG_ENDIAN so LITTLE_ENDIAN is less than BIG_ENDIAN. 
> The implementation is simplified, removing the constructor and explicit static fields. 
> Remove the override of `toString`; the javadoc provided by Enum is sufficient.
> 
> No changes to other classes or implementations are needed to pass Tier 1-3.

ByteOrder is just an enum, the get and set methods suggested belong elsewhere.  The optimizer can do the right thing relative to the enum regardless of where they are implemented.

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PR Comment: https://git.openjdk.org/jdk/pull/27657#issuecomment-3408160639