Re: Best Way to Pass Info Between Objects?

ram@zedat.fu-berlin.de (Stefan Ram) writes:


  For example, I assume that the task is given to plot a sine
  curve. How do I do this in TDP (top-down programming)? Well,

public static void main( final java.lang.String[] args )
{ final Plotter plotter = new Plotter();
  final Sine sine = new Sine();
  for( double x = -sine.start(); x < sine.end(); x += sine.step( x ))
  plotter.set( x, sine.val( x ));
  plotter.pack();
  plotter.setVisible(); }

(untested)

  Now, I still need to implement ?Plotter? and ?Sine?. I wrote
  the code intentionally as if I was not aware of the
  complications of the EDT and ?paintComponent?, I wrote it in
  a problem-oriented manner, in terms of the application
  domain, ignoring the details of Java and Swing. To be aware
  of such implementation details is left to the lower level
  classes.

  Another example. How do I write a recursive directory
  listing? I intionally do *not* read the documentation of
  java.io nor java.nio! I try to forget the little what I
  already know about them. I start to code as if I just knew
  the JLS, but not the rest of the Java SE library:

public class Main
{ public static void main( final java.lang.String[] args )
  { final Entry entry = Entry.from( args[ 0 ]);
    entry.print(); }}

interface Printer
{ public void print(); }

public abstract class Entry implements Printer
{ /* factory method */
  public static Entry from( final java.lang.String path )
  { ... } }

public class Invalid extends Entry
{ public void print()
  { java.lang.System.out.println( "invalid." ); }
  ... }

public class File extends Entry
{ public void print()
  { java.lang.System.out.println( this.path() ); }
  ... }

public class Directory extends Entry
{ public void print()
  { java.lang.System.out.println( this.path() );
    for( final Entry entry : this.iterable() )
    entry.print(); }
  ... }

(untested)

  Only then, I start to look up the given file operations
  in order to implement the details ?...?, which then
  will be partially ?bottom-up?.

  There once was a language ?Elan? that had special support
  for TDD (by which I mean ?top-down design?, here) using
  ?stepwise refinement?

http://en.wikipedia.org/wiki/ELAN_(programming_language)

  .