When to use java.util.Collection or java.util.Set

[Randahl Fink Isaksen]

Hi everybody     I noticed in the EJB 2.0 specification that most of the examples use java.util.Collection when defining a relationship between two entities, even though java.util.Set is also allowed.   Why is that so?   I would expect java.util.Set to be the most frequently used type, since in general you would not want duplicates in a relationship. Think of a Person-owns-Car relationship for instance – you are not interested in any duplicates here, since a Person cannot own the same car twice so to speak (if one relationship says that person P is the owner of car C, it does not provide you with any usefull information to create yet another relationship between P and C).   Which cmr-field-types do you use and why?     Randahl