What is class , abstract class & interface .

What is class ?

• class is blueprint from which we create object.

• we declare class with the help of class keyword.

• Inside the class, we can directly write fields (non-static / static), blocks (non-static / static), constructors, concrete methods (non-static / static), inner classes, interfaces, and so on.

• Generally, we can create object of class with the help of new keyword.

• class is also a user-defined data type.

• we cannot write abstract method inside the normal class.

Abstract Class :

• Abstract class is declare with the abstract keyword .
• We can not create object of the abstract class .
• Abstract class may contain non - abstract method ( concrete methods ) , may contain abstract method , may contain non - static field . may contain static field .
• Abstract class can not be final .
• for declare abstract class , we use abstract keyword.

Note :

• Abstract method is type of method having no body . We have to provide body of abstract method in their child class .

interface :

• Interface is a blueprint that contains abstract methods and constant (public static final) variables.
• for declare interface , we use interface keyword .
• with the help of interface , we achieve multiple inheritance .