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Inner classes do not have to be anonymous as shown in the above examples. They can be named as well.

Access specifier

Just like any other class, a class defined inside of another class can be public , protected , package private, or private .

Extensibility specifier

Just like a regular class, a final nested/inner class cannot extended.

Abstract specifier

Just like a regular class, an abstract nested/inner class cannot be instantiated.

Inheritance specifier

Just like a regular class, an nested/inner can extend any non-final class and implement any number of interfaces that are within its scope.


Nested classes are used mostly to avoid name clash and to promote and enforce information hiding. For example the specialized double precision geometric point class, Point2D.Double is defined as an nested class of Point2D which is in turn a nested class of Point . In such, it has access to all the functionality of its parent plus it avoids the name clash with the double precision number class, Double

Inner classes are used to create (at run-time) objects that have direct access to the internals of the outer object and perform complex tasks that simple methods cannot do. Most of the time, they are defined anonymously. For examples, " event listeners " for Java GUI components are implemented as inner classes. The dynamic behavior and versatility of these "listeners" cannot be achieved by the addition of a set of fixed methods to a GUI component. We shall study Java event handling soon!

An inner object can be thought as an extension of the outer object.

6. closure

In functional programming, the closure of a function ( lamdba ) consists of the function itself and an environment in which the function is well-defined. In Java, a function is replaced by a class. An inner class is only defined in the context of its outer object (and the outer object of the outer object, etc...). An inner class together with its nested sequence of outer objects in which the inner class is well-defined is the equivalent of the notion of closure in functional programming. Such a notion is extremely powerful. Just like knowing how to effectively use lambda expressions and higher order functions is key to writing powerful functional programs in Scheme, effective usage of anonymous inner classes is key to writing powerful OO programs in Java.

Some important points to remember about closures and inner classes:

  • An object's closure is defined at the time of its creation.
  • An object "remembers" its closure for its entire lifetime.
  • An inner object's closure includes any local variables that are declared as final , plus all fields of the enclosing object, including private ones.
  • Every time a factory method is run, where a new anonymous object is created, a new closure for that object is created. This is because the local variables could change between calls.
  • Closures enable decoupled communication because an inner class can communicate with its outer class through its closure.

One of the most important ways in which we will use anonymous inner classes it to take advantage of their closure properties. Anonymous inner classes are the only objects in Java that can be instantiated in such a manner that the variables in their environments (closures) can be dynamically defined. That is, since an anonymous inner class can reference a local variable (that is declared final ) and since local variables are created every time a method is called, then every the anonymous inner class object created has a different set of dynamically created variables that it is referencing. This means that we can make unique objects with unique behaviors at run time.

Questions & Answers

how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
what is system testing
what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
can nanotechnology change the direction of the face of the world
Prasenjit Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Principles of object-oriented programming. OpenStax CNX. May 10, 2013 Download for free at http://legacy.cnx.org/content/col10213/1.37
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