CSC153, Class 39: Inheritance

Summary:
* Inheritance in general
* Inheritance in Java
* Examples: Course Prerequisites

Notes:
* Did anyone attend last night's talk?
* What did you think about yesterday's class?
* No, I haven't graded homework 3.  See my plan for 
  the reasons.
* "What" can serve as a pronoun.
* Expect exam 3 on Friday.
* No, I didn't grade HW3.  Big surprise.  Read my plan
  for details.
* Cool talk noon on Friday.  More extra credit for attending.
* CS courses you might take next semester and next year.

Possible Fall CS Courses
* CSC223, Software Design, Fall. [1/2 Required]
  Every fall
* CSC261, Artificial Intelligence, Fall. [Optional]
  Every-other fall (computational linguistics the other fall)
* CSC211, Architecture [1/2 Required]
  Every-other fall (operating systems the other fall)
* 2-credit "Web programming" independent (details to
  follow next week).
  Perl, some C, SQL, lots of program management
  Probably every semester
  Details to follow
* More Math.
* ...
* Special topic on Cryptology
* CSC301, Algorithms (MAT218 prereq)
  (every fall)

Possible Spring CS Courses
* CSC201, "CS Under the Hood" (C programming and more)
  Every spring
* CSC362, Compilers  [1/2 required; alterantive with 223]
  Every-other spring (alternates with Networks; elective)
  Requires architecture
* CSC341, Theory of Computation
  Every spring
  MAT 218 prereq
* CSC302, Programming Languages
  Every spring
  CSC301 prereq
* TEC154, Evolution of Technology
  + Sam teaches it.  Yes, he can be as annoying about grading
    writing as he is about grading programming.
  + 8 a.m.
  + Required for technology studies concentration

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Back to inheritance

Important goals in software engineering
* Document well
* Code well ... which means
  + Code efficiently
  + Code elegantly
  + Code correctly
  + Code generally

Important desire for language design: Help programmers
write reusable code

Two techniques in object-oriented design that support
reuse of code
* Inheritance
* Polymorphism

What are these things?
* Inheritance:
  DaB: Objects can mutate (gain capibilities from other objects 
   and then change them).
  Sam: The ability to define new classes (subclasses) based 
   on other classes (superclasses) and automatically reuse 
   the code from the superclasses in the subclasses.

Example:
  Remember the book example we discussed a few weeks ago?
  If we've defined a book, and we need to talk about library
    books (e.g., for writing a library reservation system),
    we can just add a little bit of information to an 
    existing book class.
  Everything we write is an object.
  We might define a generic two-player game and then
   specialize it for Raquetball, Squash, Ping-Pong

* Consider the following questions for Friday
  + How does higher-orderness relate to polymorphism and
    and inheritance?
  + Why have multiple inheritance?

Inheritance in Java

public class SubClass
  extends SuperClass
{
 ...
}