RFR: 8261880: Change nested classes in java.base to static nested classes where possible [v2]

[liach]

On Wed, 17 Feb 2021 16:32:39 GMT, Сергей Цыпанов <github.com+10835776+stsypanov at openjdk.org> wrote:

>> src/java.base/share/classes/java/lang/invoke/DelegatingMethodHandle.java line 192:
>> 
>>> 190: 
>>> 191:     /* Placeholder class for DelegatingMethodHandles generated ahead of time */
>>> 192:     static final class Holder {}
>> 
>> For the four `Holder` classes in `java.lang.invoke`, the class is generated when running jlink via `java.lang.invoke.GenerateJLIClassesHelper`. To stay in sync with the definition you'd have to update that code. Also, since these `Holder` classes will only contain static methods and are never instantiated then I'm not sure it matters whether the classes are static or not.
>
> I'll just revert them

For static methods, since in java language you cannot declare static method in instance inner classes, I'd say making them static makes more sense language-wise. Also making them static reduces compiler synthetic instance field and constructors.

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PR: https://git.openjdk.java.net/jdk/pull/2589