Category "uml"

Is it recommended to make associations to enum classes in UML class diagrams?

I am designing a class diagram and I got a doubt: I have a class which have several attributes referring to Java enums and other classes that will be mapped as

Who owns the method in a sequence diagram?

Say we have the diagram: I wonder whether it's known by the diagram who owns the methods. For instance: Is pickup a method of Waiter? Is serve food then a meth