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(Although it isn't implicitly obvious, it is also possible to call any of the eleven methods defined in the Object class on an object's reference being stored as an interface type. Those eleven methods can be called on any object,including array objects, regardless of how the references are stored.)

Not the standard approach

If you are defining your own container, this is a satisfactory approach to implementation of the observer design pattern. However, you cannot use thisapproach when using containers from the standard collections framework, because those containers are designed to always store references as the generic type Object . In those cases, the casting solution of Question 7 (or the use of generics) is required.

Back to Question 8

Answer 7

C. A-intfcMethodX B-intfcMethodX

Explanation 7

The correct use of an interface

This program illustrates the correct use of an interface. It uses a cast of the interface type in the following fragment toresolve the problem that was discussed at length in Question 6 earlier.

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()

Back to Question 7

Answer 6

A. Compiler Error

Explanation 6

What is a container?

The word container is often used in Java, with at least two different meaning. One meaning is to refer to the type of an object that is instantiatedfrom a subclass of the class named Container . In that case, the object can be considered to be of type Container , and typically appears in a graphical user interface (GUI) . That is not the usage of the word in the explanation of this program.

A more generic meaning

In this explanation, the word container has a more generic meaning. It is common to store a collection of object references in some sort of Javacontainer, such as an array object or a Vector object. In fact, there is a complete collections framework provided to facilitate that sort of thing ( Vector is one of the concrete classes in the Java Collections Framework) .

Storing references as type Object

It is also common to declare the type of references stored in the container to be of the class Object . Because Object is a completely generic type, this means that a reference to any object instantiated from any class (or any array object) can be stored in the container. The standard containers such as Vector and Hashtable take this approach.

(Note that this topic became a little more complicated with the release of generics in jdk version 1.5.)

A class named Base and an interface named X

In a manner similar to several previous programs, this program defines a class named Base and an interface named X as shown in the following fragment.

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

Classes A and B extend Base and implement X

Also similar to previous programs, this program defines two classes named A and B . Each of these classes extends the class named Base and implements the interface named X , as shown in the next fragment.

Questions & Answers

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 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
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
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
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
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
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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