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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

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
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
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
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
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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