Inner Class

Group 3 Kompongsom Class

Introduction

Member : Leang BunrongChea SocheatHeak MenghokHoun SreynavBouy Sodeth

Content

• Static inner class• Local inner class• Anonymous inner class

Inner Class

Overview of Nested Class (Inner Class)

Nested Class

Non-Static Nested Class (Inner Class)

Static Nested Class

Local inner Class

Anonymous inner Class

Why Inner Class?

• A big class to small class• Easy to maintenance• Increased encapsulation

Static Inner Class

• Can use Public, Protected, Default, Private modifier• marked with static modifier. • doesn’t share any special kind of relationship with

an instance of outer class. • It can access static data members of outer class

including private.• Static inner class cannot access non-static (instance)

data member or method of its Outer class.

Static Inner Class (cont.)Example:

public class Outer {static int code=1;static String name="Cheat";static int birth=1994;static class Inner {public String toString(){return code+"\t"+name+"\t"+birth;}}public static void main(String[] args) {Outer.Inner n = new Outer.Inner();System.out.println(n.toString());}

}

Local Inner Class

• Local class can access local variable that are declare final keyword

• We can create Local class in the method• We can not declare some static member

Local Inner Class (cont.)Ex:

class Simple{ private int data=30; //instance variable void display(){class Local{void msg(){System.out.println(data);}}Local l=new Local();l.msg();}public static void main(String args[]){Simple obj=new Simple();obj.display();}

}

Anonymous Inner Class

• No-name declaration• Declared and instantiated at the same time• Must implement an Interface or extend a Class• No ‘implements’ or ‘extends’ keywords used• No Constructor• Can not define static fields, static method or

static class except constants (static final).

Anonymous Inner Class (cont.)Example:

Class MyClass{JButton button = new JButton("Click Me");button.addActionListener(new ActionListener() {

@Overridepublic void actionPerformed(ActionEvent arg0) {

JOptionPane.showMessageDialog(null, "Message", "Title", JOptionPane.ERROR_MESSAGE);

}});

}

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