Introduction To Object Oriented Programming

Build a Animal Class

• color, age, name.

We would want to create a few objects and play with them

• Understand concepts of Class, Object, State, Behavior
• Understand basics of Encapsulation and Abstraction

Procedural/Structured Programming

• Thinking in terms of procedures/methods/functions

    //Global Data

 fly(){
  trvaleToAirport();
  findEntryGate();
  findCheckInCounter();
  checkIn();
  securityCheck();
  waitForBoardingCall();
  boardTheFlight();
  takeOff();
  landing();
}

Object Oriented Programming

• Thinking about Objects
  • Class, Object
    • Data (state)
    • Actions (behaviour)

Aeroplane

• airline, make, type, position //data
• takeoff(), land(), cruise() //actions

Passenger

• name, address //data
• takeCab(), checkin(), walk(), smile() //actions

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OOP doesn't mean to "split up" code into random classes.

The ultimate goal of OOP is to reduce code duplication, improve readability and support reuse as well as extending the code.

Doing OOP means that you follow certain principles which are (among others):

information hiding / encapsulation
single responsibility
separation of concerns

https://docs.oracle.com/javase/tutorial/java/index.html

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Object Oriented Terminology

class Animal {

	private String name; // data (state)
	private int age;
	private String color;

	Animal() {
		System.out.println("Animal Constructor...");
	}

	Animal(String name, int age, String color) {
		this.name = name;
		this.age = age;
		this.color = color;
	}

Animal cat = new Animal();
Animal dog = new Animal();

Terminology

• Class - Template ex : Animal, Person, Employee
• Objects/Instances - ex : cat, dog, employee1
• Member Data/State/Fields - Data present in each object - name, color, age
• Actions/Methods/Behaviour - What actions can be performed on each object?

Animal

• name, age, color
• bark(), walk(), run(), sleep(), eat(), drink()

Abstraction and Inheritance

		abstract class Animal {
	
		private String color;
		private int age;
	
		abstract void bark();
	
		public void run() {
	
			System.out.println("running...");
		}
	
		}
		
		class Cat extends Animal { // cat is a animal
		
			public void bark() {
		
				System.out.println("Meow Meow");
			}
		
		}
		
		class Dog extends Animal {
		
			public void bark() {
		
				System.out.println("Bow Bow");
			}
		
		}