RFR: 8302818: Optimize wrapper sets and immutable sets of Enums [v5]

[Pavel Rappo]

On Tue, 21 Mar 2023 15:23:53 GMT, Claes Redestad <redestad at openjdk.org> wrote:

> An alternative design which would avoid adding more classes could be to add package-private accessors to the existing `Unmodifiable/Synchronized` wrapper classes so that `EnumSet/-Map` can retrieve the underlying set of an unmodifiable or synchronized `Set` or `Map` and then use it directly for these bulk operations. Then you'd contain the additional overhead to `EnumSet/-Map`.

Another alternative, in cases where `arg.getClass() == X.class` can be safely substituted with `requireNonNull(arg) instanceof X`, is a marker interface.

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PR Comment: https://git.openjdk.org/jdk/pull/12498#issuecomment-1478253385