RFR: 8359707: Add classfile modification code to RedefineClassHelper [v6]

[Adam Sotona]

On Thu, 26 Jun 2025 16:34:06 GMT, Chen Liang <liach at openjdk.org> wrote:

>> Java's gone overly terse, but if you look at the n-1 commit, the classModel::forEach copies everything in the class to the new class.  At least that's what Chen told me and it seems to do.  Isn't this cool?
>
>> Seriously though, which part of that is doing the actual replace??
> 
> `ClassDesc.of(newClassName)` defines a new class with the new name, and the lambda just copies everything over as-is.

It can be also written as:
`return ClassFile.of().transform(classModel, ClassDesc.of(newClassName), ClassTransform.ACCEPT_ALL`

But be aware this code does not change the class name use anywhere in the code, descriptors, handles, annotation, etc..., just the class name itself.

Full class remapping was a job of https://docs.oracle.com/en/java/javase/23/docs/api/java.base/java/lang/classfile/components/ClassRemapper.html which unfortunately didn't make it from 23 preview to 24 :(

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PR Review Comment: https://git.openjdk.org/jdk/pull/25857#discussion_r2169481261