RFR: 8275775: Add jcmd VM.classes to print details of all classes [v2]

[Ioi Lam]

On Wed, 19 Jan 2022 08:39:34 GMT, Xin Liu <xliu at openjdk.org> wrote:

> > How about this:
> > ```
> > jcmd VM.classes -verbose classname classname ...
> > ```
> >   
> > -verbose is optional
> > more than one classnames can be specified.
> > if no classnames are specified, all classes are printed
> 
> If the class name here means the "fully-qualified" class name, I guess it's not practical to input multiple classnames like "java.lang.invoke.LambdaForm$MH/0x0000000800c0b400" in cmdline.
> 
> The main cost of VM_PrintClasses should be the traversal of all classes. I feel a filter won't save much runtime time. We can leave it to the external awk scripts. What do you think?

That sounds fair. I think for filtering it's best left to external tools.

I think we should use `-verbose` as the optional argument, to be consistent with other jcmds such as ` VM.symboltable`

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PR: https://git.openjdk.java.net/jdk/pull/7105