JavaInterfacesFour kinds of inner classesMember classesMember classes IIAnonymous inner classesExample anonymous inner classStatic member classesLocal classesInterfaces, againAdaptersThe EndJavaInner ClassesInterfacesinterface KeyListener { public void keyPressed(KeyEvent e); public void keyReleased(KeyEvent e); public void keyTyped(KeyEvent e);}•An interface describes methods but does not supply bodies for them.Four kinds of inner classes•Member classes–simple•Anonymous classes–syntax is ugly but anonymous classes are useful•Static member classes (not too useful)•Local classes (not too useful)•Every class compiles to a separate .class fileMember classes•A member class is an “ordinary” inner class•class Outer { int n; class Inner { int ten = 10; void setNToTen ( ) { n = 10; } } void setN ( ) { new Inner ( ).setNToTen ( ); }}Member classes II•Member classes are useful for handling events•Button b = new Button (“Click Me”);b.addActionListener (new Clicker ( ));…class Clicker implements ActionListener { … }•Can access the variables of the outer classAnonymous inner classes•Convenient for short code•b.addActionListener (anonymous inner class);•The anonymous inner class can be either:–new Superclass (args) { body }–new Interface (args) { body }•Notice that no class name is given--only the name of the superclass or interfaceExample anonymous inner classb.addActionListener (new ActionListener ( ) { public void actionPerformed (ActionEvent e) { System.out.println (“Ouch!”);} } ) ;Static member classes•static class Inner { … }•A static member class can access only static variables of the outer class•A static member class isn't "really" an inner class•Inner classes did not exist in Java 1.0Local classes•A local class is a class defined inside a method.•A local class cannot access variables declared in the method (!)•There are many other restrictions on local classes.Interfaces, againinterface KeyListener { public void keyPressed(KeyEvent e); public void keyReleased(KeyEvent e); public void keyTyped(KeyEvent e);}Adaptersclass KeyAdapter implements KeyListener { public void keyPressed(KeyEvent e) { }; public void keyReleased(KeyEvent e) { }; public void keyTyped(KeyEvent e) { };}The
View Full Document
Unlocking...