Object and Class

It is a basic runtime entity that has

State
Behaviour
Identity

It is an instance(result) of a class. It is made up of attributes and methods

Syntax :

class_name object_name= new class_name();

Example:

 B obj= new B();         //here obj is attribute
 obj.s();                //here s() is method

Characteristics of the objects:

Feature	Description	Example (Car)
State	Represents the data/attributes of an object.	Speed, Fuel Level, Color
Behavior	Represents the functionality of an object.	Accelerate, Brake, Turn
Identity	A unique identity that distinguishes objects.	Vehicle Registration Number

Class:

Blueprint from which object is created.

It contains:

Fields
Methods
Constructor
Blocks

Syntax:

access_modifier class class_name
  {
      // var
      // method
      // constructor
      // blocks and statement. 
  }

Example: Creation of class

Access
modifier keyword class_name
   |       |        |
public   class   HelloWorld {
	public static void main(String[] args) {
		System.out.println("hello");
	}
}

Output:

hello

Accessing a Class and Calling its Members

To use a class, create an object and access its variables/methods.

Example: Calling and accessing the Class

package quipohouse;
public class HelloWorld {
	int a = 10;

	public static void main(String[] args) {

		HelloWorld obj = new HelloWorld();   // here helloWorld is a class and obj is an object
		System.out.println(obj.a);           // calling instance variable by its object
	}
}

Output: