RFR: 8282662: Use List.of() factory method to reduce memory consumption [v3]

[ExE Boss]

On Fri, 13 May 2022 12:19:25 GMT, Сергей Цыпанов <duke at openjdk.java.net> wrote:

>> Usually a method declares either no exception, or a couple of them. In the first case `List.of()` doesn't allocate, in the second it allocates an object with 1-2 fields but without an array, so `List.of()` is likely to be more memory-saving
>
> Usually a method declares either no exception, or a couple of them. In the first case `List.of()` doesn't allocate, in the second it allocates an object with 1-2 fields but without an array, so `List.of()` is likely to be more memory-saving

Even in the no exceptions case, the `exceptionTypes` array still has to be allocated/copied by `Method.getExceptionTypes()`[^1] when the `ProxyMethod` constructor[^2] is invoked.

So if anything, the `List.of(…)` call should be moved into the `ProxyMethod` constructor.
And maybe the call to `Method.getExceptionTypes()` should be changed to `Method.getSharedExceptionTypes()`[^3].

[^1]: https://github.com/openjdk/jdk/blob/e765c42aa71a25a9c30f3409b8fdc6bda6f7b639/src/java.base/share/classes/java/lang/reflect/Method.java#L340-L343
[^2]: https://github.com/openjdk/jdk/blob/e765c42aa71a25a9c30f3409b8fdc6bda6f7b639/src/java.base/share/classes/java/lang/reflect/ProxyGenerator.java#L710-L714
[^3]: https://github.com/openjdk/jdk/blob/e765c42aa71a25a9c30f3409b8fdc6bda6f7b639/src/java.base/share/classes/java/lang/reflect/Method.java#L305-L308

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PR: https://git.openjdk.java.net/jdk/pull/7729