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Figure 2 . Text output for overridden ToString method and class B.

ToString in class B

Do you recognize this?

You should recognize this as the text that was encapsulated in the String object returned by the overridden version of the ToString method defined in the class named B . (See Listing 2 .)

Overridden version of ToString was executed

This verifies that even though the reference to the object of the class B was stored in a reference variable of type Object , the overridden version of the ToString method in the class named B was executed (instead of the default version defined in the class named Object) . This is runtime polymorphic behavior , as described in a previous module.

Once again, what is the rule?

The selection of a method for execution is based on the actual type of object whose reference is stored in a reference variable, and not on the type of the reference variable on which the method is called.

An object of the class C

Finally, the code in Listing 6

  • Instantiates a new object of the class C
  • Stores the object's reference in a reference variable of type Object
  • Calls the ToString method on the reference and saves the returned string
  • Displays the returned string on the computer screen

Listing 6 . An object of the class C.

Object varC = new C(); String v3 = varC.ToString();Console.WriteLine(v3); //Pause until user presses any key.Console.ReadKey();}//end Main }//end class Polymorph04

What will the output look like?

By now, you should know what to expect in the way of text appearing on the computer screen. The code in Listing 6 causes the text shown in Figure 3 to be displayed.

Figure 3 . Text output for overridden ToString method and class C.

ToString in class C

Overridden version of ToString was called

This confirms what you should already have known by now. In particular, even though the reference to the object of the class C was stored in a reference variable of type Object , the overridden version of the ToString method defined in the class named C was executed. Again, this is runtime polymorphic behavior based on class inheritance and method overriding.

No downcasting was required

It is also very important to note that no downcasting was required in order to call the ToString method in any of the cases shown above.

Because a default version of the ToString method is defined in the Object class, that method can be called without a requirement for downcasting on a reference to any object stored in a variable oftype Object . This holds true for any of the methods defined in the class named Object .

A generic array object

Therefore, if we create an array object designed to store references of type Object , we can store (potentially mixed) references to any type of object in that array. We can later call any of the methods definedin the Object class on any of the references stored in the array.

The result will be the execution of the overridden version of the method as defined in the class from which the object was instantiated, or the versioninherited into that class if the method is not overridden in that class. Current jargon would say that the behavior of the method is appropriate for the type of object on which it is called.

Questions & Answers

why is economics important
Derrick Reply
What will you do as a consumer if you are not at equilibrium?
chukwu Reply
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Gloria Reply
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Omben Reply
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Alex Reply
What is an indifference curve?
layla Reply
different levels of utilities of a person in a given set of bundles of goods
RAM
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Mokgobo Reply
identify and quantity five social costs and social benefits of building a hospital
Mokgobo
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Jean
state the law of diminishing return?
Ibrahim
The Law of Diminishing (Marginal) Returns simply states that at some point in time a business/operation/etc.'s increased productivity will begin to decline.
The
For example, if a small pizza shop currently has 3 workers in the kitchen at any given time,and hiring 1 more worker will increase productivity, at some number of workers hired will the business see a decrease in productivity because the capital resources that the pizza shop has is not infinite.
The
Five social benefits of building a hospital, in my opinion and depending on where it's built, would be 1) Increased care for neighboring residents, 2) Potential jobs for individuals, 3) May decrease the travel time residents need to endure in order to reach the nearest hospital
The
4) May create work-study programs for individuals who aspire to be future Doctors, Nurses, Physicians, etc. 5) Assuming there are local pharmaceutical businesses nearby, the hospital may decide to purchase supplies local, increasing the business' sales. Thus, generating more income.
The
5 costs of building a hospital would be 1) Increased noise and waste pollution from service vehicles and hospital visitors, 2) May require large amounts of space, possibly jeopardizing nearby animal habitats, 3) May see an increase in traffic and possibly car accidents from frantic individuals
The
racing to see their injured friends, family members, etc. 4) Constructing a hospital and hiring staff is very expensive 5) To use funds, private or public, to finance the construction of a hospital cannot be used to fund any other projects. (The concept of opportunity costs.)
The
what is meant by inteference with the price mechanism operation?
Mugen
We use a Supply and Demand graph to illustrate at what price level will the market for a certain good or service be at equilibrium. If the price for a good or service is set too high, consumers will be less inclined to buy that product Thus, creating a surplus.
The
This surplus will eventually drive the price back down to it's equilibrium point. Similarly, if a price for a good or service is set too low, individuals would be more inclined to buy more of a certain product, creating a shortage. This shortage will cause sellers to drive the price back up to the
The
equilibrium point.
The
is it true that the opportunity cost of unemployed labour is zero?
Wisdom Reply
no
Oigebe
give two forms of collusion
nondumiso Reply
1.Explicit Collusion: Also termed overt collusion, this occurs when two or more firms in the same industry formally agree to control the market .
Gafar
2.Implicit Collusion: Also termed tacit collusion, this occurs when two or more firms in the same industry informally agree to control the market, often through nothing more than interdependent actions. A prime example of implicit collusion is price leadership .
Gafar
explicit collusion: this occurs when two or more firms in the same industry legally agree to control the market
Panashe
implicit collusion this occurs when two or more firms in the same industry illegally agree to control the market
Panashe
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nondumiso
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Godwin
reasons why a country maybe involved in international trade
Nde Reply
state five similarities and differences between money market and capital market
Victoria Reply
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Pam Reply
what is an industry
EWAH Reply
An industry is the production of goods and related services within an economy
Prabhu
an industry is place where goods and services are produced for human consumption....
Usman
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Abdulhameed Reply
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Abayneh
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Michael Reply
economics is a social sciences that deals with the production distribution and consumption of goods and services produced.its study of behaviour between economic agents
rkesh
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Ridwan
change in demand/change in variable variable may be price, income,
rkesh
in a comparison of the stages of meiosis to the stage of mitosis, which stages are unique to meiosis and which stages have the same event in botg meiosis and mitosis
Leah 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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