What are the reasons involved in using the interface?

• Interfaces are used to implement the skeleton methods and provide a way through which the class can extend other classes. 
• The example shows that a sub-class can extend the bicycle class that contains mountain bike, etc. 
• They provide lots of inherited functions and features that can be added to provide unique features. 
• They are allowed to apply one method to multiple classes and extend more than one class functionality and characteristics.
•  High level classes can be defined using the interface in this case it can consists of methods and other definitions of classes.