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In other words, the behavior of the method named test , when called on a reference to an object of type A , is different from the behavior of the method named test when called on a reference to an object of type B .

The method definitions

The definitions of the two classes named A and B , along with the two versions of the overridden method named test are shown in the following fragment.

class A extends Base{ public void test(){System.out.print("A "); }//end test()}//end class A class B extends Base{public void test(){ System.out.print("B ");}//end test() }//end class B

Store a subclass object's reference as a superclass type

The program declares a reference variable of type Base , instantiates a new object of the class named A , and assigns that object's reference to the reference variable of type Base . Then it calls the method named test on that reference as shown in the following fragment.

Base myVar = new A(); myVar.test();

Polymorphic behavior applies

Simple polymorphic behavior causes the overridden version of the method named test , defined in the class named A , (as opposed to the versions defined in class Base or class B ) to be executed. This causes the letter A followed by a space character to be displayed on the standard output device.

Store another subclass object's reference as superclass type

Then the program instantiates a new object from the class named B , and assigns that object's reference to the same reference variable, overwriting thereference previously stored there. (This causes the object whose reference was previously stored in the reference variable to become eligible for garbagecollection in this case.)

Then the program calls the method named test on the reference as shown in the following fragment.

myVar = new B(); myVar.test();

Polymorphic behavior applies again

This time, simple polymorphic behavior causes the overridden version of the method named test , defined in the class named B , (as opposed to the versions defined in class Base or class A ) to be executed. Thiscauses the letter B followed by a space character to be displayed on the standard output device.

Once again, what is runtime polymorphic behavior?

With runtime polymorphic behavior, the method selected for execution is based, not on the type of the reference variable holding the reference to theobject, but rather on the actual class from which the object was instantiated.

If the method was properly overridden, the behavior exhibited by the execution of the method is appropriate for an object of the class from which theobject was instantiated.

Back to Question 10

Answer 9

D. A

Explanation 9

Compiles and executes successfully

This program compiles and executes successfully causing the version of the method named test , which is overridden in the class named A to be executed. That overridden method is shown in the following fragment.

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

So, what is the issue here?

The purpose of this program is to determine if you understand polymorphic behavior and the role of downcasting. Consider the following fragment taken fromthe program in Question 8 .

Questions & Answers

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
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 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
How can I make nanorobot?
Lily
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
how can I make nanorobot?
Lily
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
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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