Association vs Dependency (Offbeat)

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Association vs Dependency (Offbeat)

Association vs Dependency (Offbeat)

2003-12-30 - By Gupta, Vipul

Back

Reply: 1 2 3 4 5 6 7 8 9 10 >>

Hi Ashraf,

CAn u provide a simple example for dependency as well.

Secondly, In Association - does it mean the instance of the class can be
created independently.
Meaning, in the example
Example:

Public class customer

{

....

Public Address homeAddress;

......

}

public class Address {

.....

}

Does it mean that the Address class can exist without the customer class or
Address class will exist only if Customer class is there.

Regards

Vipul

-- --Original Message-- --
From: ashraf galal [mailto:ashrafwg@(protected)]
Sent: Tuesday, December 30, 2003 10:52 AM
To: J2EEPATTERNS-INTEREST@(protected)
Subject: Re: Association vs Dependency (Offbeat)

Actually, these concepts is UML not a java. You are quite well
understanding but I would like to illustrate the difference between them and
give an example.

Dependency :

Anytime a class uses another class in some fashion, a dependency exists
between the two.

A dependency exists of a class:

- has a reference to an object directly.

- Has a local variable based on another class.

- Has a reference to an object indirectly via some operation
parameters.

- Uses a class's static operation

Also there are dependency between packages.

Association:

There is two types of association, unidirectional and bi-directional
associations.

Unidirectional association implies that an object of the class may invoke
methods on the other class.

In java, this manifest itself as an instance variables on the class that may
invoke methods.

Example:

Public class customer

{

....

Public Address homeAddress;

......

}

public class Address {

.....

}

bi-directional association means that either object in the association may
invoke methods on other.

In java, this results in an instance variable on each class based on the
type of the other class.

Example;

Public class Team

{

LinkedList teamPlayers = new LikedList();

teamPlayers.add(new teamPlayer(...));

......... }

public class teamPlayer {

Team memberOf;

....

}

Ashraf Galal
(416)804-8359
>From: ShriKant Vashishtha >Reply-To: An interest list for Sun Java Center
J2EE Pattern Catalog >To: J2EEPATTERNS-INTEREST@(protected) >Subject:
Association vs Dependency (Offbeat) >Date: Sun, 28 Dec 2003 14:17:03 -0800 >
>Hi All, > >I am slightly confused in finding the difference between
association and dependency. > >For me, whenever the variable is intialized
at a local scope or passed as a parameter in a method, its denoted as
dependency. However, for association, I believe, the object needs to be on
global scope (as an instance variable). However, I rarely use any object at
a global scope, unless I know that it is used for maintaining the state of
class or need to be used across different methods. So most of the time, I
end up with dependency . > >Am I missing something over here. > >Thanks
>-ShriKant > > >-- ---- --- -- ---- ---- ---- ---- >Do you Yahoo!? >Protect
your identity with Yahoo! Mail AddressGuard >
>====================================================================
>Companion Site: http://www.corej2eepatterns.com >J2EE BluePrints:
http://java.sun.com/blueprints/corej2eepatterns >List Archive:
http://archives.java.sun.com/archives/j2eepatterns-interest.html
>Unsubscribing: email "signoff J2EEPATTERNS-INTEREST" to
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML xmlns:o = "urn:schemas-microsoft-com:office:office"><HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859 (See http://iso-8859.ora-code.com)-1">

<META content="MSHTML 6.00.2800.1106" name=GENERATOR></HEAD>
<BODY>
<DIV>Hi
Ashraf,</DIV>
<DIV> </DIV>
<DIV>CAn u
provide a simple example for dependency as well.</DIV>
<DIV> </DIV>
<DIV>Secondly, In Association - does it mean the instance of the class can be
created independently.</DIV>
<DIV>Meaning, in the example</DIV>
<DIV>
Example: 
Public class customer
 {
  
....
  
Public Address homeAddress;
 <o:p></o:p>
  
......
   
}
 <o:p></o:p>
public class Address {
.....
}
 
Does it mean that
the Address class can exist without the customer class or Address class will
exist only if Customer class is there.
 
Regards
Vipul</DIV>
<BLOCKQUOTE>
<DIV class=OutlookMessageHeader dir=ltr align=left>-- --Original Message-- -- From: ashraf galal
[mailto:ashrafwg@(protected)] Sent: Tuesday, December 30, 2003 10:52
AM To: J2EEPATTERNS-INTEREST@(protected) Subject: Re:
Association vs Dependency (Offbeat) </DIV>
<DIV>
<DIV>
Actually, these concepts is UML not a  java.  You are quite well understanding but I
would like to illustrate the difference between them and give an example.

 <o:p></o:p>
Dependency :
Anytime a class uses another class in some fashion, a dependency exists
between the two.
A dependency exists of a class: 
-      &nbsp
; 
has a reference to an object directly.
-      &nbsp
; 
Has a local variable based on another
class.
-      &nbsp
; 
Has a reference to an object indirectly via some operation
parameters.
-      &nbsp
; 
Uses a class's static operation
Also there are dependency between packages. 
 <o:p></o:p>
Association: 
There is two types of association, unidirectional and bi-directional
associations. 
Unidirectional association implies that an object of the class may
invoke methods on the other class.
In java, this manifest itself as an instance variables on the class
that may invoke methods. 
 <o:p></o:p>
Example: 
Public class customer
 {
  
....
  
Public Address homeAddress;
 <o:p></o:p>
  
......
   
}
 <o:p></o:p>
public class Address {
.....
}
 
bi-directional association means that either object in the association
may invoke methods on other.
In java, this results in an instance variable on each class based on
the type of the other class.
 <o:p></o:p>
Example;
Public class Team 

  
{
     LinkedList  teamPlayers = new
LikedList();
     
teamPlayers.add(new teamPlayer(...));
      
......... 
}
 <o:p></o:p>
  public
class teamPlayer {
   
Team  memberOf;

    
....
 }

 <o:p></o:p></DIV>
<DIV>Ashraf Galal (416)804-8359</DIV>>From: ShriKant Vashishtha
<SHRISUBS@(protected)>>Reply-To: An interest list for Sun Java Center J2EE
Pattern Catalog <J2EEPATTERNS-INTEREST@(protected)>>To:
J2EEPATTERNS-INTEREST@(protected) >Subject: Association vs Dependency
(Offbeat) >Date: Sun, 28 Dec 2003 14:17:03 -0800 > >Hi All, >
>I am slightly confused in finding the difference between association and
dependency. > >For me, whenever the variable is intialized at a local
scope or passed as a parameter in a method, its denoted as dependency.
However, for association, I believe, the object needs to be on global scope
(as an instance variable). However, I rarely use any object at a global scope,
unless I know that it is used for maintaining the state of class or need to be
used across different methods. So most of the time, I end up with dependency .
> >Am I missing something over here. > >Thanks >-ShriKant >
> >-- ---- --- -- ---- ---- ---- ---- >Do you Yahoo!? >Protect
your identity with Yahoo! Mail AddressGuard >
>====================================================================
>Companion Site: http://www.corej2eepatterns.com >J2EE BluePrints:
http://java.sun.com/blueprints/corej2eepatterns >List Archive:
http://archives.java.sun.com/archives/j2eepatterns-interest.html
>Unsubscribing: email "signoff J2EEPATTERNS-INTEREST" to
listserv@(protected) </DIV> 
<HR>
MSN 8 helps <A href="http://g.msn.com/8HMBENCA/2743??PS=">ELIMINATE E-MAIL
VIRUSES. </A>Get 2 months FREE*.
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Site: http://www.corej2eepatterns.com J2EE BluePrints:
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listserv@(protected)</BLOCKQUOTE></BODY></HTML>
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