• Subject: Re: IBM pushing Java
  • From: email@xxxxxxxxxxxxxxxxxxx (James W Kilgore)
  • Date: Sun, 21 Mar 1999 19:40:53 -0800
  • Organization: Progressive Data Systems, Inc.


I'm going to go out on a limb here and display my own position in the
learning curve.
About a year ago I picked up about 50lbs of Java books and here is what
I've gotten out of it:

(Now my terminology will probably not be correct, but I have to
translate into lay terms so I can understand it)

One could define a "name and address" object, which would include all
rules of validation.  It does not contain data.  It is empty.

To use this object, one would create an "instance".  The instance
(usage) does contain data.
So in defining a "Customer" object, it can contain a "name and address"
object.  Even the "Customer" object is empty.  The instance or maybe a
better word may be the occurrence (This.customer) does contain the data.

>From a design point of view, the "name and address" object would not be
capable of producing labels.  A label writing object would be able to
accept, as input, a "name and address" portion of objects customer,
vendor, employee, subscriber, etc.

In analogy may be: The DDS for a physical file does not contain any
data.  In RPG we process an occurrence of the physical file (a record).

In real life, the "name and address" object would be a composite of a
"name" object coupled to an "address" object.  Therefore you would only
define the rules for a name once.  Well actually, you would have people
names and company names which would have a totally different set of
rules.  Companies don't have first, middle, last names.  OOps, that
makes "name" three different objects! =:-o

James W. Kilgore

boothm@ibm.net wrote:
> This seems to be the whole guts, right there.  In the end, we need to be 
>doing OO stuff.
> OO is mentioned through the months, and every cycle of discussions adds to my 
>decidedly low level of OO comprehension.
> Hopefully this cycle will add, too.  To help me understand the idea of OO:  
>Lets talk about a particular data object, the "name and address" object.
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