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

[Yi Yang]

On Wed, 19 Jan 2022 02:50:16 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>>> It seems it would be useful to support the verbose output with just a single class that is specified, although that would suggest that the dcmd name should then be something other than `VM.classes`.
>> 
>> This is a good idea, but `jcmd VM.classes verbose=XX` looks strange, `jcmd VM.class XX` is also not much proper, because we desire to print all classes in default(`jcmd VM.class`). an alternative is to use `jcmd VM.classes verbose | grep XX` currently.
>
>> > It seems it would be useful to support the verbose output with just a single class that is specified, although that would suggest that the dcmd name should then be something other than `VM.classes`.
>> 
>> This is a good idea, but `jcmd VM.classes verbose=XX` looks strange, `jcmd VM.class XX` is also not much proper, because we desire to print all classes in default(`jcmd VM.class`). an alternative is to use `jcmd VM.classes verbose | grep XX` currently.
> 
> I was thinking the syntax would look like:  `jcmd VM.classes [verbose [classname]]`
> 
> Your grep solution doesn't work because each class has multiple lines of output.

@plummercj Can you please help review this from the serviceability point of view? Thanks in advance!

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