Runtime.Version

[mark.reinhold at oracle.com]

2017/7/8 10:44:11 -0700, Remi Forax <forax at univ-mlv.fr>:
> this is the JDK version as specified by JEP 223 [1], this is not an
> artifact version, this is the JDK (as a whole) version.

Correct.

> The ModuleDescriptor.Version [2] is the module version, something like
> your artifact version.

Right, and it's more abstract than `Runtime.Version` for exactly the
reasons that Robert mentioned.

> The JDK version is loosely related to a module version because they
> some version components like starting with 9.
> 
> That's said, i'm not sure the JDK version is something that should be
> checked/compared in the code, after all people can build there own JDK
> with their own version.

You'd have to hack the JDK build system pretty heavily in order to use
a version string that's not parseable as a `Runtime.Version`.  I'm not
sure why anyone would do that.

>                          You can use the java.base version instead,
> there is a signing mechanism (the module hashes) that ensures that the
> jdk modules and the java.base module are compatible.

The build system ensures that the version strings of all modules, and of
the JDK itself, are the same even though module versions are represented
as instances of `ModuleDescriptor.Version` and the platform version is
represented as a `Runtime.Version`.

- Mark