creating multiple classes in file

Keep in mind that storing multiple classes per file is discouraged as a bad
practice. I strongly suggest that you split your fine into separate file per 
class + one additional file with global functions

Yes we can have multiple classes in single file but it people rarely do that 
and not recommended. We can have multiple classes in File but only one class 
can be made public. If we try to make two classes in File public, 
we get following compilation error.
“The public type must be defined in its own file”.