CSC152 2005S, Class 21: Object-oriented design and Interfaces

Admin:
* Presents
* Lecture/discussion style class
* How did Friday go?
* Questions on the exam?

Overview:
* OOD, reviewed
* Motivating example
* Basic classes
* Representing operations
* Implementing Surround
* Using interfaces

Questions on Javadoc
* How do I insert linebreaks?  <br>
* Now that we know it, do you expect us to use it?  YES
* Now that we've seen pre and postconditions, do you expect us to use them? YES
* Even on the exam?  IT WOULD BE NICE

Questions on the Exam?
* Should we turn in our tester (if we write one) for problem 2?  YES
* Should we turn in our fraction class, since we have to update it, for problem 3?  YES

Object-oriented programming:
* Programs are built from objects, which combine data and capabilities
* We look for three key ideas in doing oop
  + Encapsulation
  + Inheritance
  + Polymorphism

Sam's silly motivating example: Laying out text on the screen

******************************************************************
* FFFFF ourscore and seven years ago our forefathers and mothers *
* F     did something which I now forget because it's much later *
* FFF
* F
* F

Description:
  * An object that represents the big F (SimpleTextBlock)
  * An object that represents the "ourscore ... later"
  * The two objects are placed side-by-side
  * The result is surrounded by stars

Our goal: Build objects and "other stuff" to make it easier to
do things like the above "programatically"

What simple classes might we build to contribute to our "text layout" program?
* TextLine (line or part of a line like a string, but may have different capabilities)
  * print, given a PrintWriter
  * Or "convert to String", so that we can print it using a PrintWriter
  * Determine the width
* SimpleTextBlock
  * Determine the width
  * Determine the number of lines
  * Get one line

What advanced operations might we include?
* Emphasize
* Surround with asterisks
* Reformat a single line onto many lines, given a particular width
* Break a sentence into lines containing certain number of words
* Search