Explain nested classes (or outer and inner classes) in java?, JAVA Programming

Assignment Help:

 

In Java not all classes must be described separate from each other. You may put the definition of one class under the definition of another class. The class inside class is called an inner class and the enclosing class is called an outer class. So when you prepare an inner class, it is a member of the outer class in much the similar way as other members like attributes, constructors and methods.

 

Where should we need inner classes? Code without inner classes is hard to maintainable and readable. When you use private data members of the outer class, the JDK compiler provides package-access member functions in the outer class for the inner class to use the private members. That leaves a security hole. We could avoid it using inner classes. Use inner class only when an inner class is only in the context of the outer class and/or inner class may be prepared private so that only outer class can access it. Inner classes are needed primarily to implement helper classes like Comparators, Iterators etc which are needed in the context of an outer class.

 

Member inner class

Anonymous inner class

public class MyStack {

private Object[] items = null;

...

public Iterator iterator() {

return new StackIterator();

}

//inner class

class StackIterator implements Iterator{

...

public boolean hasNext(){...}

}

}

public class MyStack {

private Object[] items = null;

...

public Iterator iterator() {

return new Iterator {

...

public boolean hasNext() {...}

}

}

}

 

Class Type

Description

Example +

Class name

 

Outer

class

Package

member class or interface

Top level class. Only type JVM

can access.

//package scope

class Outside{}

 

Outside.class

Inner

class

static nested

class or interface

Defined within the context of the

top-level class. Must be static & can access static members of its having class. No relationship between the instances of outside and Inside classes.

//package scope

class Outside {

static class Inside{       }

}

 

Outside.class ,Outside$Inside.class

Inner

class

Member class

Defined within the context of

outer class, but non-static. Until an object of Outside class has

been started you can't create

Inside.

class Outside{

class Inside(){}

}

 

Outside.class , Outside$Inside.class

Inner

class

Local class

Defined within a part of code.

Can use final local variables and final method parameters. Only

visible within the part of code that defines it.

class Outside {

void first() {

final int i = 5;

class Inside{}

}

}

 

Outside.class , Outside$1$Inside.class

Inner

class

Anonymous

class

Just like local class, but no

name is used. Useful when only one instance is used in a

method. Most naturally used in

AWT/SWING event model, Spring framework hibernate call

back methods etc.

//AWT example

class Outside{

void first() {

button.addActionListener ( new ActionListener()

{

public void actionPerformed(ActionEvent e) { System.out.println("The button was  pressed!");

}

});

}

}

 

Outside.class , Outside$1.class

 

 


Related Discussions:- Explain nested classes (or outer and inner classes) in java?

Write a note on java beans, Question 1 Explain the data types in Java ...

Question 1 Explain the data types in Java Question 2 Write a note on StringBuffer Question 3 What is Exception? Question 4 Write a note on stream classes Questi

Programing, A servey is done in M.P. by forest department finding different...

A servey is done in M.P. by forest department finding different types of species of birds the servey data covered four major cities indore,Bhopal,Gwalior,vidhisa. The result they o

How to construct objects with new operator, How to Construct objects with n...

How to Construct objects with new operator? class Car { String licensePlate; // e.g. "New York 543 A23" double speed; // in kilometers per hour double maxSpeed;

Explain booleans in java, Explain Booleans in java? Booleans are named ...

Explain Booleans in java? Booleans are named after George Boole, a nineteenth century logician. Every boolean variable has one of two values, true or false. These are not the s

What are the advantages of multimedia presentations, What are the advantage...

What are the advantages of multimedia presentations? Write any five. Multimedia presentation is a excellent tool for effective communication: Advantages: 1. Easy to make l

Create a program using constructors, Create a program Using Constructors? ...

Create a program Using Constructors? The further program uses the constructor to initialize a car rather than setting the areas directly. class CarTest7 { public static voi

Application to control robot arm , I send you these files in order to make ...

I send you these files in order to make clear image about my task that I want you to design for me an application for PC that used to control robot arm via micro controller PIC18.

Give an example for using getter methods, Give an example for Using Getter ...

Give an example for Using Getter Methods ? class CarTest6 { public static void main(String args[]) { Car c = new Car(); c.setLicensePlate("New York A45 636"); c.setMa

Use of unicastremoteobject in rmi, What is the use of UnicastRemoteObject i...

What is the use of UnicastRemoteObject in RMI? Ans) The UnicastRemoteObject class gives support for point-to-point active object references using TCP streams. Objects that need

Write a xhtml document with java script, Write an XHTML document that uses ...

Write an XHTML document that uses JavaScript code to do the following.  The user is first prompted for a word and then for a possible prefix for that word.  If the prefix is not an

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd