Designing Elegant Solutions through Interface Magic The topic of interfaces. An interface resembles an abstract class but there are a few differences. With the abstract class, you can create method declarations and implemented methods. Child classes can then inherit an abstract class and override or implement its methods. With an interface, you can only define the functionality. You can’t actually implement anything. The biggest difference is that a child class can only extend one abstract class but it can implement multiple interfaces. You will hear the term contract when talking about interfaces meaning that once you implement it, you are obligated