Re: how to implement association relationship in Java

From:

LaieTechie <laie@win_remove_get_nospam_solutions.com>

Newsgroups:

comp.lang.java.programmer

Date:

Wed, 08 Nov 2006 02:05:53 -0700

Message-ID:

<pan.2006.11.08.09.05.50.552126@win_remove_get_nospam_solutions.com>

On Sat, 04 Nov 2006 02:46:04 +0000, newsnet customer wrote:

Hi,

I want to implement as association relationship in Java. I understand the
implementation for this kind of relationship is called "containment".
However, I can not find the code for this on the internet. From what is
explained on the internet, I believe the code would look something like
this:

/*A Car 'has a' Wheel relationship*/

public class wheel{
    public wheel(){
    }
    }
}
public class Car{
    Wheel w;

    public Car(){
        w = new Wheel();
    }
    }
}
Is this the basic idea?
by the way, what does containment mean?

ST

There are two types of relationships you should concern yourself with in
Java:

Has A: this indicates containment. In you example, a Car has a Wheel.
Your container class should have a member property ("instance variable")
of that type.

Is A: this denotes inheritance. A Car is a vehicle. You indicate
inheritance with "extends" (for classes) or "implements" (for interfaces).

Public class Car extends Vehicle {}

You may also run into "uses" relationships, which may translate into
instance variables or local variables (variables defined within a certain
scope, like a method).

HTH,
La`ie Techie