You could add/edit the jar manifest to include/specify which class is the startign point.
See http://docs.oracle.com/javase/tutorial/deployment/jar/appman.html for more details.
I did add the Manifest. Here is what the Manifest looked like. Should it be in the src folder or outside of the src folder? But the manifest did not help me access the jar file. I even tried to java -jar JAR-name (ie java -jar NicholasGame.jar )on the command prompt and it worked but for the average user this is weird to perform just to open a game.