You have uncompressed the *.jar file.
To run the application, either:

1. Run the *.jar file.
    On windows, double clicking the jar file may work.
    On a console (linux, windows or mac), navigate to the folder containing the jar file and type:
     java -jar <name of jar>
    where <name of jar> is the name of the *.jar file.
    On most platforms, appending or dropping the extension is irrelevant.

2. Run the uncompressed version.
    On a console, navigate to this folder and type:
     java main.Main