Usage and importance of Abstract and Interface

Question

Accepted Answer

Abstract and Interface are important concepts in object-oriented programming.

Abstract classes provide a way to define common behavior for a group of classes.
Interfaces define a contract that classes must adhere to.
Abstract classes can have both abstract and non-abstract methods.
Interfaces can only have abstract methods and constants.
Classes can implement multiple interfaces but can only inherit from one abstract class.
Abstract classes can have constructors, while interfaces cannot.
Abstract classes can have instance variables, while interfaces cannot.
Interfaces allow for better code reusability and maintainability.
Abstract classes allow for code sharing and provide a common base for related classes.
Example: An abstract class 'Animal' can have abstract methods like 'eat()' and non-abstract methods like 'sleep()'.
Example: An interface 'Drawable' can have a method 'draw()' that different classes like 'Circle' and 'Rectangle' can implement.

Accepted Answer

After Java8 provided option to put default and static method It is little mixed up when differentiating between interface and abstract class. I see few differences including the BOT :

1) Interface is still interface, so If a class want to implement interfaces than it can implement more than one interface but a class can extend only one abstract class.

2) Interfaces are useful for functional programming in java.

Usage and importance of Abstract and Interface

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