Software Engineering I
Sept. 6, 2013

Instance Variables for Classes
  -list of variables for a class dentoting data that may be present in each
   instance
  -Attributes represent properties of the object

Example: Employee
         -name
         -dob
         -ssn
         -telNum
         -address

Association - relationship between one class and another

Example - supervisor association relates class Employee to class Manager
          tasksToDo association relates class Task to class Employee

Recall that variables and objects are not the same in Java.

In Java, variables _refer_ to objects.  That is, variables are references.

The _type_ of a reference determines what classes it may refer to.

Instance vs. class variables

  Recall that each instance of a class has its own set of instance variables.

  Recall that each class has exactly one set of class variables that are 
  shared among instances.

  +----------------+
  | Employee       |
  +----------------+
  | name           |
  | dob            |
  | address        |
  | title          |
  | num_employees  |  <-- notice that class variables are underlined
  | -------------  |
  +----------------+
  
  +----------------+
  | Tyler:Employee | <--Tyler is an instance of the Employee class
  | -----          |
  +----------------+
  | name="Tyler"   | <--Instance variables exist for each instacne of the class
  | dob="9/2/1977" |
  | address="Here" |
  | title="Dev."   |
  +----------------+

Methods, Operations, and Polymorphism

 Method - procedural abstraction used to define functionality of a class
 Operation - more abstract than procedure, may be independent of code.
 Polymorphism - having many forms
   Examples include method overloading or overriding