Interfaces

- Interfaces are another common form of abstraction…that's supported by many object-oriented languages.…An interface is a programming structure…that declares a set of methods for a class to implement,…but the interface itself doesn't contain any functionality.…There's no implemented code or behavior.…It's just a collection of method signatures…to specify a service.…For example, in Java an interface…would be written like this,…using the word interface instead of class.…This interface is named Moveable…and it declares one method called move.…

But that method doesn't have a body.…Again, you're not allowed to put any functionality…inside an interface.…When we defined a new class…and choose to implement a specific interface,…it's like signing a contract,…promising that the new class we're defining…will implement all of the methods in that interface.…But, we're free to implement the inner workings…of those methods however we want as long as the method…names, inputs, and outputs match the interface.…For example, if we define an Asteroid class that implements…