<< Chapter < Page Chapter >> Page >

(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

Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
Application of nanotechnology in medicine
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
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
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
hi
Loga
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
Privacy Information Security Software Version 1.1a
Good
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply

Get the best Algebra and trigonometry course in your pocket!





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
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Object-oriented programming (oop) with java' conversation and receive update notifications?

Ask