Software Engineering I
Sept. 4, 2013

Review of Object Oriented Programming
  -Using Java because you should be familiar with it

Object Oriented Systems use abstraction to make SW less complex

Abstraction (partial definition) - expressing the qualities of objects
and being able to visualize them without needing a complete definition.

Abstraction helps you to avoid worrying about some of the details of
programming and helps you to focus on the real problem. 

Object oriented programming uses both procedural and data abstraction.

Procedural abstraction - abstracting functions/methods/routines

  - Pass in parameters and get output
  - Don't worry about how it works (black box)

  Example - a summation function

  int sum(int [] intArray);

  We don't need to look at the inside of the function to understand how it
  should work.

  Procedural abstraction is fine by itself for functionality that doesn't
  need to be associated with an object (e.g. static methods).

Data abstraction

  Records or structures were the first types of data abstraction.

  This is grouping data together.

  Example:

  public class PlayingCard
  {
    public String suit;
    public int faceValue;
  }

Object Oriented Paradigm
  Perform computing in the context of objects

  Objects are instances of programming constructs (in our case classes), which
  may include both data and procedural abstractions to operate upon the objects

Procedural vs. Object Oriented Programming

OOP

         +------------------+
         |  Account         |
         +------------------+
         |  Credit()        | 
         +------------------+
         |  Debit()         | 
         +------------------+
                  ^
                 / \
                 ---
                  |
             +----+------+
             |           |
   +---------+-----+   +-+-------------+
   | CheckingAcct  |   | SavingsAcct   |
   +---------------+   +---------------+
   | CompInterest()|   | CompInterest()|
   | ComputeFees() |   | ComputeFees() |
   +---------------+   +---------------+

Procedural

            +----+
            |main|
            +----+
              |
        +--------------------------------------+
        |         Perform Transaction          |
        +--------------------------------------+
        |      |            |               |
  +------+  +-----+ +--------------+  +--------------+
  |Credit|  |Debit| |CompInterest  |  |CompFees      |
  +------+  +-----+ | if checking  |  |if checking...|
                    | elseif saving|  +--------------+
                    +--------------+

Objects are instances of a class
  Groups of data in a structured format with functionality specific to that
  structure.

An object may have both attributes and specific functionality (methods).

  Attributes describe the object's current state and characterize the object.
  Functionality shows how the object can react to change in state

UML Example of Objects (not classes)

  +--------------------+    +--------------------------+
  | SavingsAcct 13264: |    | Jane:                    |
  | ------------------ |    | -----                    |
  +--------------------+    +--------------------------+
  | balance = 2316.22  |    | dob = 6/3/1978           |
  | opened = 4/5/2012  |    | addr = "800 Univ. Dr"    |
  |                    |    | position = Manager       |
  +--------------------+    +--------------------------+

Object Oriented Analysis

  - Decide which objects to save and which are important
  - Determine structure, relationships, and behavior of objects
  - Can figure out physical representation later

Classes - units of data abstraction that define the structure of instances

  All objects with the same properties and behavior are instances of a class

  Example - an employee like Jane

Methods - behaviors of objects

When should you define a class?

  When you see something that can be clearly defined as a single member of
  a class and can be reused

Naming classes
  Start with a capital letter, All words in class name start with a capital
  letter.
  Typically name after a real world object.
  
  Examples: Doctor, Hospital, Employee, PartTimeEmployee

  Creating classes can be an art.  Don't be too general or specific.

Instance variables
  - properties of classes
  - contain class data
Different kinds of instance variables exist
  attributes - about the class (e.g. a name for an employee)
  associations - relationships of one class to another (supervisor to employee)