Interfaces Outline Generic interface versus Java interface What

Interfaces • Outline: – Generic interface versus Java interface – What a (Java) interface is: • • Its syntax What it says What it does NOT say How it is used, why it is useful – How interfaces are used in Word. Games • UML class diagram for Word. Games – Word. Games • An application of interfaces Fundamentals of Software Development 1 1

Generic interfaces • Generic computer-science interface – The “face” that one entity shows others: • What services it provides • What information it expects – Physical examples: • • • Computer Interfaces Stethoscope Telephone Camera Toaster Fundamentals of Software Development 1 2

Why have interfaces? • A Java interface is the “face” that one class shows others – An interface contains the signature but not body for each method – Any class that implements an interface must provide the methods listed in the interface • So an interface specifies a contract Example of a Java interface public interface Clock. Radio { public Time get. Time(); public void set. Time(Time x, Station s); } Fundamentals of Software Development 1 3

Why have interfaces? public interface Clock. Radio { public Time get. Time(); public void set. Time(Time x, Station s); } • Java interfaces are important because: – They provide for software reuse. For example: • • • Interfaces can I provide a String. Transformable interface You provide classes that implement String. Transformable (and should) be used as types Our separately-written code works together seamlessly! – They provide genericity. For example: • My code declares each of your things as a String. Transformable thing • You provide various implementations of String. Transformable – e. g. Capitalizer, Name. Dropper, Ubby. Dubber, … • My code is generic – it doesn’t care what implementation of String. Transformable you supply! Fundamentals of Software Development 1 4

UML class diagram for Word. Games All our stuff The String. Transformable interface is how our code knows how to “connect” to your code <<interface> String. Transformable -------------transform(String) : String Capitalizer Fundamentals of Software Development 1 Name. Dropper xxx … xxx Questions on this important idea? 5

Java Interfaces: Summary public interface Clock. Radio { public Time get. Time(); public void set. Time(Time x, Station s); } • A Java interface is the “face” that one class shows others – An interface contains the signature but not body for each method – Any class that implements an interface must provide the methods listed in the interface • So an interface provides a contract • Java interfaces are important because they provide for: – Software reuse – Genericity Fundamentals of Software Development 1 From now on, “interface” means “Java interface” to us 6