The proper syntax to run a jar file is as follows:
$ java -jar filename.jar
If you are as facing the same error after trying the above command then try passing the package and classname with the command, something like this:
$ java -cp filename.jar com.packagename.classname
And even if this doesn't work then I think you have not created an executable jar file. Refer to this link to know how to create an executable jar.