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In some cases, multiple methods have the same name, but different formal argument lists. This is polymorphism implemented using overloaded methods. I explained this form of polymorphism in an earlier module.

In other cases, multiple methods have the same name, same return type, and same formal argument list. This is method overriding , which is the main topic of this module.

The essence of runtime polymorphic behavior

Methods are called on references to objects. Typically, those references are stored in reference variables, or in the elements of a collection such as anarray, stack, or queue.

The decision process

With runtime polymorphism based on method overriding , the decision regarding which version of a method will be executed is based on the actual type of the object whose reference is stored in the reference variable, and not on the type of the reference variable on which the method is called.

Stated differently, the type of the reference determines which methods can be called . The type of the object determines which method (from that set of allowable methods) will be called .

Late binding

The decision regarding which version of the method to call cannot be made at compile time. That decision must be deferred and made at runtime. This issometimes referred to as late binding .

Operational description of runtime polymorphism

Here is an operational description of runtime polymorphism as implemented in C# through inheritance and method overriding:

  • Assume that a class named SuperClass defines a method named method .
  • Assume that a class named SubClass extends SuperClass and overrides the method named method .
  • Assume that a reference to an object of the class named SubClass is assigned to a reference variable named ref of type SuperClass .
  • Assume that the method named method is then called on the reference variable using the following syntax: ref.method() .
  • Result: The version of the method named method that will actually be executed is the overridden version in the class named SubClass . The version that is defined in the class named SuperClass will not be not executed.

This is runtime polymorphism.

Runtime polymorphism is very powerful

As you gain more experience with C#, you will learn that much of the power of OOP using C# is centered on runtime polymorphism using class inheritance,interfaces, and method overriding. (The use of interfaces for polymorphism will be discussed in a subsequent module.)

An important attribute of runtime polymorphism

This is worth repeating:

The decision regarding which version of the method to execute is based on the actual type of object whose reference isstored in the reference variable, and not on the type of the reference variable on which the method is called.

Why is it called runtime polymorphism?

The reason that this type of polymorphism is often referred to as runtime polymorphism is because the decision regarding which version of the method to execute cannot be made until runtime. The decision cannot be made at compiletime (as is the case with overloaded methods).

Questions & Answers

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
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Anassong
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
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I start with an easy one. carbon nanotubes woven into a long filament like a string
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many many of nanotubes
Porter
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what is the function of carbon nanotubes?
Cesar
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what is nanomaterials​ and their applications of sensors.
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what is system testing?
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how to synthesize TiO2 nanoparticles by chemical methods
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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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