Class

• A class is simply a representation of a type of object.


• It is the blueprint/ plan/ template that describe the details of an object.


• It contains state(instance variables) and behaviour (methods).


• A template that describes the kinds of state and behaviour that objects of its type support.

Example:-

Class Employee
{
  //code......
}			

Object:-

• An Object is a real world entity.


• An object can be considered a "thing" that can perform a set of related activities.


• The set of activities that the object performs defines the object's behavior.

For Example:

amit is an object of class Employee.

Employee tkhts = new Employee();
				

Instance Member:-

• Instance variables are non-static.


• There is one occurrence of an instance variable in each class instance.


• It is also known as a member variable or a field.

Example of an instance variable:-

class Employee
{
 int id;
  //code......
  //code......
}

Class Member:-

• Class variables are called static variables.
• There is only one occurrence of a class variable per JVM per class loader.
• When a class is loaded the class variables are initialized.
• A static variable is used in the singleton Design pattern.
• A static variable is used with a final modifier to define constants.

Example of a class variable

class Employee
{
  static int id;
  //code......
  //code......
}