Object oriented principles

1. Agenda
● Object
● Class
● Data Hiding
● Exercise
● Inheritance
● Library/App

3. Object & Class
✔ Object: State and Behavior
✔ Class : Blueprint/template
→ Variables
State
→ Methods
Behavior

4. Class Vehicle{
int speed;
void move();
}
Example

5. Object.Method Notation
Class Calculator{
int subtract(int a, int b){
return a – b;
}
int sum(int a, int b){
return a + b;
}
}
Calculator calculator = new Calculator();
calculator.sum(3, 4);
calculator.subtract(5, 2);

6. Data Hiding
● Restricting Access
→ Access modifiers

7. Scope of Variables
The scope of a variable defines the section of the code in which the variable is
visible
Instance variables
Instance variables are those that are defined within a class itself and not in any
method or constructor of the class. They are known as instance variables
because every instance of the class (object) contains a copy of these variables
Argument variables
These are the variables that are defined in the header oaf constructor or a
method. The scope of these variables is the method or constructor in which they
are defined.
Local variables
A local variable is the one that is declared within a method or a constructor (not in
the header). The scope and lifetime are limited to the method itself.

8. Identifying Objects in the System
Splitting responsibility
Modularized code
Meaning full code

9. Identifying Objects in the System
Library Management System
Library Attender
Student or …
Book

10. Identifying Objects in the System
Exercise
Hotel Management
(Identify methods
in the objects as well)

11. Inheritance
Subclass can inherit the definitions of one or
more general classes
Employee
|
Manager

12. ● When ?
→ IS-A relationship
● How ?
→ extends keyword
● Method Overloading
→ precedence
● Example
Inheritance

13. Example and Exercise
Vehicles – Ex: Car, Truck, Bike etc
Implement any two Vehicles using inheritance

14. Packages
Util
Math
Trignometric
Algebraic
Scientific
Electric
RelativeMotion
WorkForce
Calendar

15. Java Library
Huge Library
DataStructures
Utilities Math, Calender
System related

16. Documentation
Java Docs
https://docs.oracle.com/javase/7/docs/api/
Example
https://docs.oracle.com/javase/7/docs/api/java/util/Arra
yList.html

17. IDE