• Subject: RE: OO Programming?
  • From: "Joe Teff" <JoeTeff@xxxxxxxxxxxxx>
  • Date: Sun, 21 Jan 2001 12:55:40 -0600
  • Importance: Normal


>The other day I had a Java programmer explain to me that
>the OO difference is not necessarily how you develop one
>program using a bunch of different classes and objects
>but rather how they are stored in memory when they are

OO is all about modeling your software to look like your
real-world environment. It takes it a step farther by
introducing abstraction, inheritance, encapsulation and
polymorphism. All of these concepts when used properly
make your system more scalable, maintainable, adaptable
and reusable. I would say that your Java programmer has
master the language syntax, but not the concepts of OO.

>Only one copy of a program is stored in memory in Java
>and all programs making a call to that particular program
>are always referencing that same one.

The class is loaded into the JVM the first time it is
referenced. Then you would make instances of it. Think of
a blueprint to make buildings. The class is a blueprint and
each building you make is an object. You can't open the
door on a blueprint and walk in. You first must make a
building based on the blueprint. That is what classes and
objects are.

It is also possible to use threads for multiple flows of
execution within a single object. That is how servlets work.
Think of executing a subroutine or calling a procedure in
your RPG program, except that your mainline continues to
execute at the same time that your subroutine/procedure is

>Is this also true for RPGILE type programming?


You can simulate many of these things in RPG/ILE now, but
requires considerable effort and knowledge of the system.
With Java, the language was built on these concepts, so they
are quite simple to implement. It does require that you
learn the OO concepts to do it well.

Joe Teff
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