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?

Ocr captcha solving, I'm seeking to hire someone to build me a program that...

I'm seeking to hire someone to build me a program that can solve a php captcha. It should be a web service or script. You will write it in any language since i will execute i ca

Write code in javascript language to show the odd numbers, Write code in Ja...

Write code in JavaScript language to show the odd numbers among 20 to 100 using FOR statement. Note: No requirement to write whole HTML program. Just JavaScript code of need p

Bidirectional currency conversion, Write a AXIS2 SOAP Java Web Service that...

Write a AXIS2 SOAP Java Web Service that performs a bidirectional currency conversion for the following currencies- GBP, EUR and USD (American Dollar). You are allowed to hardco

Development of an application using jade agent toolkit, You need to build a...

You need to build an agent system using the JADE Toolkit that allows the lecturer of FIT5031 to broadcast their availability and arrange for consultation with students in a dynamic

Kik messenger program, Kik Messenger is a plan mobile messenger like Skype....

Kik Messenger is a plan mobile messenger like Skype. It's available on each major smart phone for Android and Iphone. Here is the entire process: Could be able to add multipl

We are in need of programmer, We are in need of Programmer In search of ...

We are in need of Programmer In search of someone who know java well enough to work under my in-house programmer and take work form him to keep the project moving. The project d

What is constraints explain with example, What is Constraints explain with ...

What is Constraints explain with example? One of the purposes to use constructors and setter techniques rather than directly accessing fields is to enforce constraints. For exa

Arraya, what is arrays and how do they operate

what is arrays and how do they operate

Describe invoking methods in java, Describe Invoking Methods in java? c...

Describe Invoking Methods in java? class Car { String licensePlate = ""; // e.g. "New York 543 A23" double speed = 0.0; // in kilometers per hour double maxS

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