Java 212: Interfaces Intro to UML Diagrams

1. Java 212: Interfaces Intro to UML Diagrams

2. UML Class Diagram: class Rectangle • +/- refers to visibility • Color coding is not part of the UML diagram

3. Interfaces • Definition: A class that contains onlyabstract methods and/or named constants • Abstract methods are methods that have no body • The body for those methods should be written inside any class that “implements” the interface • Typically used as a software design parameter during the design phase of an application. • Also sometimes used as a workaround on Java’s limitation of not allowing multiple inheritance • Java allows classes to implement more than one interface • eg: If you want a class to respond to different kinds of events (ActionEvent, WindowEvent, MouseEvent, etc), you can have a class implement all of these interfaces.

4. public interface Animal { public void speak(); public void eat(); } public class Dog implements Animal { public void speak() { System.out.println("Woof"); } public void eat() { //code to display bone, kibbles } } public class Whale implements Animal { public void speak() { System.out.println("Squeak"); } public void eat() { //code to display little fish, plankton, etc } } An Interface with two implemented classes

5. Interfaces In our discussion of GUIs, we discussed the use of inner (nested) classes to handle events. In these cases, we implemented the interface by creating a whole new inner class. However, we could just as easily declared an outer class as ‘implementing’ the interface. public class RectangleCalculator implements ActionListener { … or even public class RectangleCalculator implements ActionListener, WindowListener, MouseListener { //declares that this class implements three interfaces…

6. Two Interface Definitions: public interface WindowListener { public void windowOpened(WindowEvent e); public void windowClosing(WindowEvent e); public void windowClosed(WindowEvent e); public void windowIconified(WindowEvent e); public void windowDeiconified(WindowEvent e); public void windowActivated(WindowEvent e); public void windowDeactivated(WindowEvent e); } public interface ActionListener { public void actionPerformed(ActionEvent e); }