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Otherwise, a cast is required

In order to call any method other than one of the eleven methods in the above list , (on an object's reference being stored as type Object without using generics) , you must cast the reference to some other type.

Casting to an interface type

The exact manner in which you write the cast will differ from one situation to the next. In this case, the problem can be resolved by rewriting the programusing the interface cast shown in the following fragment.

void doIt(){ Object[]myArray = new Object[2];myArray[0] = new A();myArray[1] = new B();for(int i=0;i<myArray.length;i++){ ((X)myArray[i]).intfcMethodX(); }//end for loopSystem.out.println(""); }//end doIt()

The observer design pattern

By implementing an interface, and using a cast such as this, you can store references to many different objects, of many different actual types, each ofwhich implements the same interface, but which have no required superclass-subclass relationship, in the same container. Then, when needed, youcan call the interface methods on any of the objects whose references are stored in the container.

This is a commonly used design pattern in Java, often referred to as the observer design pattern.

Registration of observers

With this design pattern, none, one, or more observer objects, (which implement a common observer interface) are registered on an observable object. This means references to the observer objects are stored in a container by theobservable object.

Making a callback

When the observable object determines that some interesting event has occurred, the observable object calls a specific interface method on each of theobserver objects whose references are stored in the container.

The observer objects execute whatever behavior they were designed to execute as a result of having been notified of the event.

The model-view-control (MVC) paradigm

In fact, there is a class named Observable and an interface named Observer in the standard Java library. The purpose of these class and interface definitionsis to make it easy to implement the observer design pattern.

(The Observer interface and the Observable class are often used to implement a programming style commonly referred to as the MVC paradigm.)

Delegation event model, bound properties of Beans, etc.

Java also provides other tools for implementing the observer design pattern under more specific circumstances, such as the Delegation Event Model, and inconjunction with bound and constrained properties in JavaBeans Components.

Back to Question 6

Answer 5

C. A-intfcMethodX B-intfcMethodX

Explanation 5

More substantive use of an interface

This program illustrates a more substantive use of the interface than was the case in the previous programs.

The class named Base

The program defines a class named Base as shown in the following fragment.

class Base{ public void inherMethod(){System.out.print("Base "); }//end inherMethod()}//end class Base

The interface named X

The program also defines an interface named X as shown in the next fragment. Note that this interface declares a method named intfcMethodX .

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
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 did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit 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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