1. Introduction to Object-oriented Programming

2. Introduction
Classes and class relationships are defined using UML Class diagrams
These classes must be implemented
Any OOP language can be used
Visual Basic C#
Java
C++

3. Key Terms (Programming Object)
Programming objects are designed to mimic real-world objects
Television set / DVD
Objects have two important characteristics
State: Current data about the object
A dog has a name, color, etc…
Behavior: Things the object can do
A dog can bark, fetch, sit, etc..,
The text boxes and buttons with which you are familiar are programming objects

4. Key Terms (Class)
A class is a template or building block for an object
We say that an object is an instance of a class
We create several bicycles from the same template

5. Key Terms (Inheritance)
Some classes have share characteristics with other classes
Mountain bikes, road bikes, etc… all have shared characteristics
OOP allows us to inherit state and behavior from other classes
The parent classes is called the superclass
The derived class is called the subclass

6. Key Terms (Interface) Here, we are not referring to user interface
We refer to the methods and properties of a class that are exposed to the outside world
In its most common form, an interface is a group of related methods with empty bodies
Classes can then implement an interface

7. Key Terms (Package)
A package is a namespace that organizes a set of related classes and interfaces
The Java platform itself is made up of many different packages that you can use
In fact, Android uses its own set of Java packages

8. Benefits of OOP
Modularity: Objects are generally independent of other objects
Information hiding: The internal implementation of an object is hidden from the outside world
Implementation vs. interface
Code re-use: Objects can be reused by many other programs

9. Declaring a Class Classes are declared inside of a class block
Properties and methods appear inside of the class block

10. Declaring a Class (Example 1)
Declare a class named Bicycle
class Bicyle { }

11. Access Modifiers (public)
public members are globally accessible and available to other assemblies (components)
Globally available within the component too
Note that Intellisense technology will display exposed members
Members of the .NET Framework class library are public for example

12. Access Modifiers (private)
private members are part of the implementation
They are exposed only to the class containing the declaration
Private members are not visible to other components
Private members are not visible to other classes

13. Access Modifiers (protected)
Protected members can only be accessed from their own package

14. Declaring a Method (Introduction)
Remember that methods perform an action
In C#, methods are nothing more than procedures
These are the same procedures that you have used before

15. Declaring a Method (Example)
Create a method named Area
public class Circle {
public double Area(double argRadius)
return 3.14 * radius * radius; }

16. Constructors (Introduction)
A constructor is a procedure having the same name as the class
The declaration looks like a method but has no return type
Constructors may accept 0 or more arguments
For example, the StreamReader constructor accepts a file name as its argument
The constructor executes automatically when the developer creates a class instance
A constructor is never called directly

17. Constructor (Example)
Create a constructor to increment an instance counter
public Circle() {
CallCount++; }

18. Static Members (Introduction)
By default, members are instance members
One instance exists for each class instance
Think of a TextBox. One instance of the Text property exists for each control instance
static members belong to the type so one copy exists for all class instances
Declare shared members with the static keyword

19. Static Members (1)
You need not create a class instance to reference a static member
The members of the System.Math class are static, for example
Only one data copy of static members exist regardless of the instance count
Include the static keyword in variable or procedure declarations

20. Why? Static Members (2) Shared members cannot operate on instance data
Instance members can operate with shared data
Why?