Objects

Objects:

• An Object is instance of a class.Objects in java can be dynamically created by using operator new.
Syntax:
ObjectReference = new ClassName();
Example
• a = new Rectangle();
• b = new Rectangle();
Note: Where Rectangle is a ClassName and a,b are object references.

Object Reference

• It is a variable in which we can store ID of an Object. Each Object has a unique ID. An object reference can be defined just like variables.
Syntax:
ClassName ReferenceList;
Example
• Rectangle a,b,c;
Note: Due to this 3 object references will be created in which we can store id of objects.

Object Initialization

• Whenever an object is created space is reserved for objects data members.

            Rectangle a,b;
            a = new Rectangle();
            b = new Rectangle();

Member Access Operator

• Members of an object can be access by using member access operator.

• Data members
• Length
• Breadth
• Member Functions
• Area()
• Perimeter()

  class Rectangle
  {
    int length;
    int breadth;
    void area()
    {
      int a=length*breadth;
      System.out.println("Area is "+a);
    }
    void perimeter()
    {
      int p=2*(length+breadth);
      System.out.println("Perimeter is"+p);
    }
  }
  class demo
  {
    public static void main(String args[])
    {
      rectangle a;
      a = new rectangle();
      a.length=5;
      a.breadth=7;
      System.out.println(a.length);
      System.out.println(a.breadth);
      a.area();
      a.perimeter();
    }
  }
  

  5 
  7 
  Area is 35 
  Perimeter is 24

Encapsulation

• Data encapsulation is a mechanism of bundling the data, and the functions that use them.
• This can be achieved in Java by defining a class.

Abstraction

• Data Abstraction is a process of providing only the essential details to the outside world and hiding the internal details.
• This can be achieved by declaring data members as private and member functions as public.

• Data members
• radius
• Member Functions
• Area()
• circumference()

  class Circle
  {
    int R;
    void area()
    {
      double a=3.14*R*R;
      System.out.println("Area is "+a);
    }
    void circuimference()
    {
      double c=2*3.14*R;
      System.out.println("Circumference is"+c);
    }
  }
  class demo
  {
    public static void main(String args[])
    {
      Circle a;
      a = new Circle();
      a.R=5;
      System.out.println(a.R);
      a.area();
      a.circuimference()
    }
  }
  

  5
  Area is 78.5 
  Circumference is 31.4