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Defining a Class in Java
Let us define a class circle:
class circle
{
//Data Members
double radius; // used for storing the radius of the circle
//Member Methods
void input() // Accepts the radius from the user
void area() // Calculates the area of the circle
void diameter() // Calculates the diameter of the circle
}
Here, "radius" is data member or attribute and "input ()", "area ()" and "diameter ()" are the member methods.
3.3 OBJECT IN JAVA
In everyday life, we encounter various objects, such as books, school uniforms, and buildings. These objects have
their own characteristics (attributes) and behaviours (methods), which are based on the structure or blueprint from
which they were created. For example, if "Fan" is a class, then individual fans produced by different companies are
objects of that class.
An object in Java is an instance of a class that contains the characteristics (attributes) and behaviours (methods)
defined by the class. Objects are the fundamental units of Object-Oriented Programming, and we can say that an
object is an implementation of a class. The key components of an object are:
• Characteristics or Attributes: These are properties that define the state of an object. They help distinguish one
object from another by holding unique values for each instance.
• Behaviour or Methods: These are actions or operations that an object can perform, defined by the methods
in the class.
• Name of the Object: Each object can have a unique name, allowing it to be identified and referenced within a
program.
3.3.1 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();
Definition
Constructor is a function or method that has same name as that of the class and used for
initializing an object created by the class.
Note: In Java, if you do not define a constructor for a class explicitly, the Java compiler provides a default
constructor implicitly.
Creating objects for class Circle:
public static void main ()
44 Touchpad Computer Applications-IX

