Sadegh Aliakbary

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Agenda Inner classes Anonymous inner class 3

Class Types class FriendlyClass{ } public class OuterClass { private int value; public class Inner{ public void f(){ … } JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source4 Friendly Class Public class Inner Class

Inner Classes Declared in another class Instantiated using a reference object of outer class Has access to this object The inner class can be static No reference object of outer class is needed No access to outer class is provided JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source5

public class OuterClass { private int value = 2; class Inner{ public void innerMethod(){ OuterClass.this.value = 5; } public void outerMethod(){ Inner inner = new Inner(); inner.innerMethod(); } public static void main(String[] args) { OuterClass outer = new OuterClass(); System.out.println(outer.value); outer.outerMethod(); System.out.println(outer.value); } JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source6 OuterClass.this is implicitly saved in inner object

public class OuterClass { private int value = 2; class Inner{ public void f(){ OuterClass.this.value = 5; } public static void main(String[] args) { OuterClass outer = new OuterClass(); OuterClass.Inner inner = outer.new Inner(); System.out.println(outer.value); inner.f(); System.out.println(outer.value); } JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source7 Why we need outer reference?

class OuterClass { static class Inner{ public void f(){ System.out.println("f() invoked"); } public class MainClass { public static void main(String[] args) { OuterClass.Inner in = new OuterClass.Inner() ; in.f(); } JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source8

Inner Class Specifiers static final Access Specifiers public private Friendly (no specifier) protected JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source9

Anonymous Inner Class An inner class With no name Created once Used once No access to this class from any other place Once created and used JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source10

interface Inner{ void innerMethod();} public class OuterClass { private int value = 2; public void outerMethod(){ Inner inner = new Inner() { public void innerMethod() { OuterClass.this.value = 5; } }; inner.innerMethod(); } public static void main(String[] args) { OuterClass outer = new OuterClass(); System.out.println(outer.value); outer.outerMethod(); System.out.println(outer.value); } JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source11

Anonymous Inner Class Usually implements an interface Or extends another class And Overrides some special method Main Application : Event Handlers JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source12

public class MyFrame extends JFrame{ JButton button; JTextField textbox; public MyFrame(){ button = new JButton("Click!"); button.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { JOptionPane.showMessageDialog(null, textbox.getText()); } }); add(button); textbox = new JTextField(10); add(textbox); } JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source13

JAVACUP.ir Contents redistribution is allowed if JAVACUP is noted as the source14