Interfaces

In this section we will cover the following :

1. What are interfaces and what are they used for?
2. Declare interfaces
3. Implement interfaces

What are Interfaces

Interfaces are 100% abstract classes. Interfaces define method definitions but does not provide the implementation. Each class that implements the interface must provide its own implementation.

An interface is like a contract. The methods it defines are mandatory and any class that implements the interface should provide the implementations.

What are interfaces used for?

1. An interface defines a contract. Interfaces guarantees that if any class implements the interface, the classes are guaranteed to have those methods available.
2. Interfaces allow multiple inheritance in Java. In Java a class can only inherit from one parent class.
3. Interfaces decouples the definition from its implementation. The concept is similar to C++ header definition and implementation which are defined in separate files.