Difference Between Abstract Classes and Interfaces

Abstract Classes Vs Interfaces

• Abstract Classes can have concrete methods while Interfaces can have only abstract methods.
• Abstract Classes can have fields and constants while Interfaces can have only constants(public static).
• Abstract Classes can have Private and Protected members while Interfaces can have only Public.
• A Class can extend from only one Abstract Class but can implement any number of Interfaces
• Abstract Classes can provide a default implementation while Interfaces can only provide the signature
• Abstract Classes are used for defining the core functionality of a class while Interfaces are used for defining the peripheral functions of a class.
• Abstract Classes are faster than Interfaces as Interfaces require time to find the actual method in the corresponding class.
• Adding/Modifying an Interface will involve searching every implementation and modifying it while this can be avoided for Abstract Classes by providing a default behavior.