Please clarify: do you want an Instance singleton or a Class singleton across multiple
VM's?  These are two very distinct concepts.

An Instance singleton across multiple VMs is accomplishable in one of many ways, as
already described by previous posts.

A Class singleton across multiple VMs isn't difficult either;  simple overload the
classloading method to

1) check for a file lock
2) load class if no lock, or throw ClassNotFoundException if lock exists
3) place file lock if Class successfully loaded

Gene
--- Ramakrishna N <[EMAIL PROTECTED]> wrote:
> Hi,
>    This is an off topic suggestion that I am seeking but its urgent and so I
> am posting it here.
>     I want only one Instance of a particular Class to be running across
> multiple VMs. I mean if I am executing a class in one of the VMs then If I
> say run the same Class in another VM of the same machine it should not run.
> How do I achieve this behaviour ?
>     Currently we have a configuration xml file where in the Application
> registers when it has opened and registers again when it has successfully
> closed so that in between if I try to open the application in another VM the
> application first reads the configuration xml and understands that one
> istance of the application is running and so it exits.
>     I would like to achieve it through ClassLoaders. Say custom
> ClassLoaders. I am sure there should be a way to achieve this without doing
> any I/O operations like opening a socket when the application starts..
>     Any help on this would be of great help. Thanks in advance.
>
> Thanks & Regards,
> kris
>
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