OOP(Object Oriented Programming) Part 1

Variables

• Static variable
• Non-static variable

Static Variable
A static variable is a variable that belongs to the class, not to a specific object.

• Declared using the static keyword.
• Only one copy of the variable is created.
• It is shared by all objects of the class.
• It can be accessed using the class name.

public class Student {
    static String college = "College";
    public static void main(String[] args){
       System.out.println(Student.college);
}
}

Non-Static Variable

A non-static variable belongs to a specific object of the class.

• It is declared without the static keyword.
• Each object gets its own copy.
• Its value can be different for each object.
• It is accessed using an object.

public class Student {
    String name;
    public static void main(String[] args){
    Student s1 = new Student();
    s1.name = "Ganapathi";
    Student s2 = new Student();
    s2.name = "Kumar";
    System.out.println(s1.name);
    System.out.println(s2.name);
}
}

Java OOP(Object Oriented Programming):

Object-Oriented Programming (OOP) is a programming paradigm based on the concept of objects that contain data (fields) and behavior (methods). It focuses on designing software that closely represents real-world entities.

Class

• A Class in Java is a blueprint or template used to create objects.
• It defines the properties (data) and behaviors (methods) that objects of that class will have.

Java Class Naming Rules

• Meaningful name
• Start's with uppercase
• No space allowed
• No special character allowed[$,_]
• Cannot start with a number

public class SuperMarket
{
//-----------
}

Object

• An Object in Java is an instance of a class that represents a real-world entity.

• It is used to access the variables and methods defined inside a class.

• State: Represents the current data or attributes of an object.

• Behavior: Represents the actions that an object can perform.
  

public class Student {
    String name;
    public static void main(String[] args){
    Student s1 = new Student();
    s1.name = "Ganapathi";
    Student s2 = new Student();
    s2.name = "Kumar";
    System.out.println(s1.name);
    System.out.println(s2.name);
}
}