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An inherited virtual method can be overridden by every class that inherits it, resulting in potentially many differentoverridden versions of a given method in a class hierarchy.

Listing 3 . Definition of class C.

class C : B { public override String ToString() {return "ToString in class C"; }//end overridden ToString()}//end class B

Behavior of overridden version

The behavior of this overridden version of the method is similar to, but different from the overridden version in the class B.

In this case, the method returns a reference to a String object that can be used to confirm that this overridden version of the methodhas been executed.

The driver class

Listing 4 shows the beginning of the driver class named Polymorph04 .

Listing 4 . Beginning of the driver class.

public class Polymorph04 { public static void Main() {Object varA = new A(); String v1 = varA.ToString();Console.WriteLine(v1);

A new object of the class A

The Main method of the driver class begins by instantiating a new object of the class A, and saving the object's reference in a reference variable of type Object , named varA .

It is very important to note that even though the object was instantiated from the class named A , the reference was saved as type Object , not type A.

Call ToString method on the reference

Then the code in Listing 4 calls the ToString method on the reference variable named varA , saving the returned reference to the String object in a reference variable of type String named v1 .

Display the returned String

Finally, that reference is passed to the WriteLine method, causing the String returned by the ToString method to be displayed on the computer screen. This causes the text shown in Figure 1 to be displayed.

Figure 1 . Text output for ToString method and class A.

A

Default ToString behavior

What you are seeing here is the String produced by the default version of the ToString method, as defined by the class named Object . The default implementation of the ToString method returns the fully qualified name of the type of the object. In this case, the object was instantiated from the class named A (so the type of the object is A ) .

Class A does not override ToString

Recall that our new class named A does not override the ToString method. Therefore, when the ToString method is called on a reference to an object of the class A, the default version of the method is executed, producing the output shown in Figure 1 .

A new object of the class B

Now consider the code shown in Listing 5 , which instantiates a new object of the class named B , and stores the object's reference in a reference variable of type Object .

Listing 5 . A new object of the class B.

Object varB = new B(); String v2 = varB.ToString();Console.WriteLine(v2);

Call ToString and display the result

The code in Listing 5 calls the ToString method on the reference of type Object , saving the returned reference in the reference variable named v2 . (Recall that the ToString method is overridden in the class named B .)

As before, the reference is passed to the WriteLine method, which causes the text shown in Figure 2 to be displayed on the computer screen.

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
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
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
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
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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