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Not runtime polymorphic behavior

Just for the record, the above invocation of the method does not constitute runtime polymorphism (in my opinion) . I included that invocation of the method to serve as a backdrop for what follows.

If this is runtime polymorphism, it is not a very significant example, because there was no requirement for the runtime system to decide betweendifferent methods having the same name. The runtime system simply executed a method belonging to an object using a reference of the same type as the object.

This is runtime polymorphic behavior

However, the call to the method in Listing 4 does constitute runtime polymorphism.

Listing 4 . This is runtime polymorphic behavior.

//Following will also compile // and run due to polymorphic// behavior. ((A)var).m();

The statement in Listing 4 casts the reference down to type A and calls the method named m on that reference.

The method output

Here is the punch line. Not only does the statement in Listing 4 compile and run successfully, it produces the following output, (which is exactly the same output as before) :

m in class B

The same method was executed in both cases

Very important

It is very important to note that this output, (produced by casting the reference variable to type A instead of type B ) , is exactly the same as that produced by the earlier call to the method when thereference was cast to type B . This means that the same version of the method was executed in both cases.

This confirms that even though the type of the reference was converted to type A , (rather than type Object or type B ) , the overridden version of the method defined in class B was actually executed.

This is runtime polymorphic behavior in a nutshell.

The version of the method that was executed was based on the actual type of the object, B , and not on the type of the reference, A . This is an extremely powerful and useful concept.

Another invocation of the method

Now take a look at the statement in Listing 5 . Will this statement compile and execute successfully? If so, which version of the method will be executed?

Listing 5 . A failed attempt.

//Following will not compile //var.m();

(That was easy. The answer to the question is given in Listing 5 ) .

Compiler error

The code in Listing 5 attempts, unsuccessfully, to call the method named m using the reference variable named var , which is of type Object . The result is a compiler error, which reads something like the following:

error CS0117: 'object' does not contain a definition for 'm'

Some important rules

The Object class does not define a method named m . Therefore, the overridden method named m in the class named B is not an overridden version of a method that is defined in the class named Object .

Necessary, but not sufficient

Runtime polymorphism based on class inheritance requires that the type of the reference variable be a superclass of the class from which the object (on which the method will be called) is instantiated.

At least this requirement is true if a significant decision among methods is to be made.

Questions & Answers

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
Do somebody tell me a best nano engineering book for beginners?
s. Reply
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
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
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
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
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
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
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
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
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Xna game studio. OpenStax CNX. Feb 28, 2014 Download for free at https://legacy.cnx.org/content/col11634/1.6
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