An introductory idea of OOP using Java

1. Saugata Bose
Introduction to OOP using Java

2. Different Programming Paradigms
 Structured Programming
 Object Oriented Programming
Java is an Object Oriented Language
Objects
Class
Inheritance
Encapsulation

3. Example of a Java Code
class Hello {
public static void main(String[] args) {
System.out.println(“Hello World !!!”);
}
}
Hello.java
C:javac Hello.java
C:java Hello
Class
Name
Hello.
class

4. OS/Hardware
machine code
C source code
hello.c
gcc
hello.exe
Platform Dependent
JVM
Java source code
hello.java
javac hello.class
OS/Hardware
Platform Independent

5. Objects Everywhere
Name
Height
Weight
Eye Color
mrBean
myLamp
Color
Height
Identity
Properties

6. Objects have state… …

7. Objects have behavior… …

8. Then what are objects… ….
 How to interact with program?
 Service Provider
A class represents a concept, and an object
represents the embodiment of a class

9. Objects and Classes
Bank
Account
John’s Bank Account
Balance: $5,257
Bill’s Bank Account
Balance: $1,245,069
data
methods

10. Java Software
Person
Sakib Tamim
“Tamim”Sakib: Say your
name
class Person{
String
askName(Person obj){
System.out.println(
"My name is
"+obj.toString());
}
}
class Main{
public static void
main(String[] args){
Person
shakib=new Person();
Person
tamim=new Person();
shakib.askName(ta
mim);
}
}

11. Inheritance
Class Hierarchy
Generalization and Specialization

12. Encapsulation
 Separation
Why Java then?
Modularity
Information Hiding
class A{
int
noOneCanSeeMe=5;
int display(){
System.out.println("Any
one can see me");
}
}
Access Modifiers
public
private
public