Abstract Class vs Interfaces
Abstract Class
An abstract class is a class that contains 0 or more abstract methods.
An abstract class can contain instance variables and concrete methods in addition to abstract methods.
We cannot declare a class as both abstract and final
It is possible to derive an abstract class as a subclass from a concrete super class
Abstract class and method is declared by using the keyword
abstract.All the abstract methods of the abstract class should be implemented in its subclasses
We cannot create an object to abstract class.
The reference of abstract class can not refer to individual methods of its subclasses
The reference of abstract class can be used to refer to objects of its subclasses
Interface
An interface cannot implement another interface.
It is possible to write a class within an interface.
An interface can extend another interface.
An interface is a specification of method prototypes.
An interface will have 0 to more abstract methods which are all public and abstract by default
None of the methods in an interface can be private, protected or static
We cannot create an object to an interface, but we can create a reference of interface type
When an interface is written, any third party vendor can provide implementation classes to it
Interface forces the implementation classes to implement all of its methods.
Abstract Class Vs Interfaces
| Abstract Class | Interfaces |
|---|---|
| An abstract class is written when there are some common features shared by all the objects | An interface is written when all the features are implemented differently in different objects |
| When an abstract class is written, it is the responsibility of the programmer to provide subclasses to it | An interface is written when the programmer wants to leave the implementation to the third-party vendors |
| Abstract methods and concrete methods can coexist in an abstract class | An interface contains only abstract methods |
| An abstract class can contain instance variable also | An interface can not contain instance variables |
| All the abstract methods of the abstract class should be implemented in its subclasses | All the methods of interface should be implemented in its implementation classes |
Abstract class is declared by using the keyword abstract | Interface is declared using the keyword interface |
⌖ core java programming abstract class differences interfaceAlso know when to use abstract classes and interfaces