Your class btnSaveListener must be in a file named btnSaveListener.java in the directory guestList (because that's the name of the pacakge that the class is in). It will not work if you put this in a file named gList.java.
The name of the file must always be the same as the name of the public class that is in the file.
You should also put the base directory that contains the package directory in the classpath, so you should put "L:\My Projects\MyJavaApps" in the classpath, not "L:\My Projects\MyJavaApps\guestList".
I added to the classpath and think it solved this problem as I am now getting 58 errors!
One of the errors it has picked up is this:
Initially, I had the miglayout folder in the 'MyJavaApps' folder, with the classpath pointing to it and it worked perfectly. Now I've added the above to the classpath, I get the above error. i've even tried moving the miglayout folder to the guestList directory, but still no luck.
I'm sorry if this is all really basic stuff.
EDIT: Forgot to mention that I didn't overwrite the classpath with the above, I added it on to the end.