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2.2 OBJECT
Occurrence of a class that contains characteristics and behaviour of the same class are called objects. In other words,
objects are the instance of a class. Thus, an object implements a class. The different components of an object are:
• Characteristics or attributes • Behaviour or methods • Name of the object
2.2.1 Creating Objects of a Class
Instance of a class is also called an object and creating an object of a class is called instantiation. Syntax of creating
an object:
<class_name> <object_name> = new <constructor>;
For example:
book computer = new book();
The new is a keyword used to create an object of a class. The book() is a constructor. A constructor is a function or
method that has the same name as the class and is used for initialising an object created of the class “book”.
Taking the above example:
public class ObjectExample
{
public static void main ()
{
Square sq= new Square (); // an object named sq of
class Square has been created
sq.accept(); // Calling accept() method of sq object s
sq.area(); // Calling area() method of sq object
sq.perimeter(); // Calling perimeter() method of
sq object;
}
}
}
Here, “sq” is the object created with the help of the “new” operator. Also “accept()”, “area()” and “perimeter()”
functions of the object sq are called.
2.3 PROPERTIES OF CLASS AND OBJECT
Class and object have some properties. Let us discuss them in detail.
2.3.1 Class is an Object Factory
Factories are places that produce products of the same kind. In the same way, a class acts as a factory as it is used to create
similar types of objects with different characteristics and common behaviours. Hence, a class is called an object factory.
The this keyword is used to refer to the current instance of the class within instance methods and constructors. It
allows you to access instance variables and methods of the current object.
For example:
// Define a class called Bus
class Bus
{
String color; // Fields (attributes)
String model;
// Constructor
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Elementary Concept of Objects and Classes 27

