Re: The San Francisco Project

[Vern Hamberg <hambergv@xxxxxxxxxxxxxx>]

Booth

At 07:46 PM 11/14/97 -0500, you wrote:
>on 11/14/97at 02:57 PM, the Great and Grand  Wazir Vern Hamberg
><hambergv@goldengate.net> said:
>
>
The San Francisco project's downloadable
>
>stuff is Windows 95 only.  So what's the point?  Are they trying to
>
>out-Windows Windows?
>
>
But the Java classes are not Windows-specific. Once you get them
>
downloaded, you can put them anywhere, right?
>
>I sure hope I am wrong (that would not be a wild new experience btw) but
>my reading was that it was 95/NT only.  I even responded to the site's
>comment button and got a pleasant reply.  It seemed patronizing to me as
>non-Win95 user so I just deleted it and plan to forgot about Java for
>awhile.

Just some more of MHOs—

I think San Franscisco is something to look at "later". Commercial versions
of VA for Java have 2 CDs, one for OS/2 & one for Windows. I don't remember
whether the entry version has both available, but I'd hope so.

>From my own perspective, there's a lot to learn before I could utilize SF
effectively. In addition, the version you can download for now is mostly a
show-and-tell kind of thing. The real thing needs to be installed on some
kind of server for production work, from what I can tell.

My recommendation, FWIW, is to get VA for Java Professional for yourself,
or get your sales rep to back-order the Enterprise version. Then get the
AS/400 Toolkit for Java and import it into VA for Java. The entry version
of VA for Java, BTW, can only have 100 classes in a project, so the Toolkit
can't be installed into it. There's plenty that can be done with those 2
packages alone. And much can be written that can run native on the 400
(with the pre-release thing installed), so long as you stay away from the
graphical interface stuff.

Different post—

>Different question:  Why are objects called  "classes"?  What is the
>entomology?  Anyone know?

To be strict about it, objects are not called classes. A class is more of a
description or specification or template, according to which an object will
be created. An analogy that works for me is that class is to object as
datatype is to variable. An object, in another manner of speaking, is an
instance of a class.

The history of the terms comes from the growth of object orientation, as
far as I can tell. OO tries to deal with things in real-world terms, and
the concept of objects and classes seems to do with the idea that objects
can be separated according to various classes. Another parallel is the idea
of genus in the animal kingdom. Such-and-such animal is of the genus
so-and-so. Similarly, we can talk about such-and-such object is of the
class so-and-so. E.g., in Java, we can use the statement 'AudioClip meow =
new AudioClip();' This creates an object named 'meow' of the Class
'AudioClip'. This object has various attributes (filename, type of clip,
etc.) that the class specifies, which can be set by various means that the
class also defines. There are also methods, or behaviors, that can be
executed, using the attributes of the object (play the clip, e.g.).

We actually have the same kind of thing in RPG, would you believe, when we
define a variable. You could think of the datatypes as classes, so that we
have 'character', 'packed', and 'zoned' classes. For our purposes, these
typically have only one attribute—their value. And there are only certain
operations that can be done on each. We cannot concatenate packed or zoned
variables with character variables. We cannot do addition on character
variables. These things are not _formally_ defined in RPG, but they could
be, and are in Java.

If I understand this stuff at all, it has taken a while to do so. It does
seem to make sense to me now, in a real-world kind of way. All I can say
is, read anything you can. Get the Sun tutorial, which discusses this stuff
quite a bit. Get one or more of the OO books—eventually the ideas will fall
into place, I believe. Get Hostmann & Cornell's book, Core Java. They
discuss some of the history.

HTH

Vernon Hamberg
Systems Software Programmer
Old Republic National Title Insurance Company
400 Second Avenue South
Minneapolis, MN 55401
(612) 371-1111 x480


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