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An anonymous class that extends an existing class

The program illustrates the use of an anonymous class that extends the WindowAdapter class, to instantiate an object to handle window events fired by the close button in theupper-right corner of the Frame object shown in Figure 2 . This class also uses the source-listener event model, and uses an instance initializer todisplay the name of the class file.

The screen output

The program produces the screen output shown in Figure 4 when

  • The program is started
  • Each button shown in Figure 2 is clicked once in succession, going from left to right
  • The close button in the upper-right corner of the Frame object in Figure 2 is clicked

When the close button is clicked, the program produces the last line of text in Figure 4 and terminates. I will identify the code that produces each line of output text in the discussion of the program that follows.

The controlling class

The controlling class for the program is shown in Listing 1 .

As you can see, the controlling class is very simple, with the main method instantiating an object of the GUI class. This results in the GUI that is pictured in Figure 2 .

Local and anonymous classes inside GUI constructor

The local class and the three anonymous classes are defined inside the constructor for the GUI class.

(Recall that local classes and anonymous classes are defined inside code blocks, which often place them inside methods and constructors, but you canalso place them inside static initializer blocks and instance initializers.)

The first four lines of the output text in Figure 4 are produced by constructors and instance initializers in the local and anonymous classes.Therefore, those four lines of text are produced when the new object of the GUI class is instantiated.

The GUI class

As is often the case, the GUI class used to create the visual GUI shown in Figure 2 consists solely of a constructor. Basically, this constructor

  • places three buttons in the frame and
  • registers event handlers on the buttons and on the frame.

Once the GUI object is constructed and appears on the screen, all furtheractivity in the program occurs under control of the event handlers associated with the buttons and the frame.

(You can learn more about event handling here .)

The GUI constructor

The GUI class, and the constructor for that class begin in Listing 2 .

As you can see, the GUI class extends Frame , so that an object of the class is a frame.

The constructor code shown in Listing 2 simply sets values for the layout, size, and title properties of the frame.

The BaldButton class

The definition of the BaldButton class begins in Listing 3 . This is a local class that extends Button .

Extending the Button class makes it possible to override the processMouseEvent method in order to handle mouse events that are fired by the button.

This is a form of low-level event handling that will be contrasted with source-listenerevent handling later in the program.

Listing 3 shows the constructor for the BaldButton class.

Enable mouse events

The most important code in the constructor is the statement that enables mouse events on the button.

Questions & Answers

what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
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
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
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 ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
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.
Virgil
is Bucky paper clear?
CYNTHIA
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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