Re: "How do you arrive at classes?"

From:
jomarbueyes@hotmail.com
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 15 Jan 2015 09:05:03 -0800 (PST)
Message-ID:
<89b236d1-f2f8-4cb8-be5d-27e634aad248@googlegroups.com>
On Tuesday, January 13, 2015 at 11:58:00 PM UTC-5, Stefan Ram wrote:

I keep simplifying and simplifying my Java course:
  during the first 40 hours all programs have one single
  class declaration only!
 
  Now, a student asked me: =BBHow do you arrive at classes?=AB,
  in the sense of: =BBHow do you get to know which classes
  should be declared in your code, especially when there
  is more than one class declaration in the program?=AB.
 
  (It might have a slight subtext, that he expects =BBreal
  programs=AB to have multiple classes [which is not even wrong!].)
 
  His question made sense, since I have very rarely or never
  shown them programs with multiple class declarations!
  (I showed already some =BBadvanced=AB stuff like non-static
  method declarations, and simple JavaFX windows with
  method literals, but all in a single class.) For example:
 
public class Main extends javafx.application.Application
{ public void start( final javafx.stage.Stage window )
  { final javafx.scene.control.TextField text
    = new javafx.scene.control.TextField( "10" );
    text.setOnAction
    ( e ->
      { text.setText
        ( java.lang.String.valueOf
          ( 3 * java.lang.Integer.valueOf
            ( text.getText() ).intValue() )); });
    final javafx.scene.Scene scene
    = new javafx.scene.Scene( text );
    window.setScene( scene ); window.show(); }}
 
  This was /all/ explained, they know method interfaces,
  but not yet programs with multiple class declarations.
 
  I tried to answer the question =BBHow do you arrive at
  classes?=AB in the classroom, kind-a stuttering, because
  I was not prepared for this question. Now, I am curious:
  How would /you/ answer this question?
 
  (An answer like =BBhigh cohesion, low coupling=AB might still
  be too abstract. Can you find a reasonable answer that a
  beginner can understand? They know non-static fields and
  non-static methods [both use and declaration], variables,
  common statements and expressions, instance creation
  expression, references, reference variable and parameters.
  So a good answer would be =BBhands-on=AB and build directly on
  these terms. What of the OOA/OOD rules can be most easily
  comprehended by a beginner?)


Hi,

I hope I'm not too lake. Take a look at:

Wirfs-Brock, R., B. Wilkerson, and L. Wiener, Designing object-oriented sof=
tware1990, Englewood Ciffs, NJ: Prentice Hall.

The book explains in plain English how to arrive at classes.
(I find this book much better than Wirfs-Brock's more recent book:
Wirfs-Brock, R. and A. McKean, Object Design: Roles, Responsabilities, and =
Collaborations 2002 Addison Wesley.)

HTH

Jomar

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