how to run a jar, from another jar.

Hi.

As the subject suggests. I am trying to run an application bundled in a
jar1 file, the from that jar1 file, I would like to run the jar2 file
and close jar1.

The idea is that jar1 is an updater and will check online and install
updates to jar2, then jar2 (the main app) will start up, close jar1,
and update jar1 (if neccessary). The thing that Im struggling with is
how to actually run the jar2 file.

Thanks for your help!

.