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

2002-04-16 Thread 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

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

2002-04-16 Thread Greg Davis 



What 
if Person P steals car C? If I were the police I would want to know he 
stole it three times. :-) Although in most cases I would tend toward a Set 
before collections, Logging is one of the areas where P C being the key 
could exist multiple times and I would want the information. I would hope 
that you datasource would not have duplicate records in it anyway. 
:-)

  -Original Message-From: Randahl Fink Isaksen 
  [mailto:[EMAIL PROTECTED]]Sent: Tuesday, April 16, 2002 9:12 
  AMTo: Orion-InterestSubject: When to use 
  java.util.Collection or java.util.Set
  
  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