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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

can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
im not good at math so would this help me
Rachael Reply
I'm not good at math so would you help me
what is the problem that i will help you to self with?
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris 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?
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
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele 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, 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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