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class A extends Base implements X{ public void inherMethod(){System.out.print( " A-inherMethod ");}//end inherMethod()public void intfcMethodX(){ System.out.print("A-intfcMethodX "); }//end intfcMethodX()}//end class A class B extends Base implements X{public void inherMethod(){ System.out.print(" B-inherMethod "); }//end inherMethod()public void intfcMethodX(){System.out.print("B-intfcMethodX "); }//end intfcMethodX()}//end class B

Concrete definitions of the interface method

As before, these methods provide concrete definitions of the method named intfcMethodX , which is declared in the interface named X .

An array of references of type Object

The interesting portion of this program begins in the following fragment, which instantiates and populates a two-element array object (container) of type Object . (In the sense of this discussion, an array object is a container, albeit a very simple one.)

void doIt(){ Object[]myArray = new Object[2];myArray[0] = new A();myArray[1] = new B();

Store object references of type A and B as type Object

Because the container is declared to be of type Object , references to objects instantiated from any class can be stored in the container. The code in theabove fragment instantiates two objects, (one of class A and the other of class B ), and stores the two object's references in the container.

Cannot call interface method as type Object

The code in the for loop in the next fragment attempts to call the method named intfcMethodX on each of the two objects whose references are stored in the elements of the array.

for(int i=0;i<myArray.length;i++){ myArray[i].intfcMethodX(); }//end for loopSystem.out.println(""); }//end doIt()

This produces the following compiler error under JDK 1.3:

Ap136.java:24: cannot resolve symbol symbol : method intfcMethodX ()location: class java.lang.ObjectmyArray[i].intfcMethodX();

What methods can you call as type Object?

It is allowable to store the reference to an object instantiated from any class in a container of the type Object . However, the only methods that can be directly called (without a cast and not using generics) on that reference are the following eleven methods. These methods are defined in the class named Object :

  • clone ()
  • equals(Object obj)
  • finalize()
  • getClass()
  • hashCode()
  • notify()
  • notifyAll()
  • toString()
  • wait()
  • wait(long timeout)
  • wait(long timeout,int nanos)

Overridden methods

Some, (but not all) , of the methods in the above list are defined with default behavior in the Object class, and are meant to be overridden in new classes that you define. This includes the methods named equals and toString .

Some of the methods in the above list, such as getClass , are simply utility methods, which are not meant to be overridden.

Polymorphic behavior applies

If you call one of these methods on an object's reference (being stored as type Object) , polymorphic behavior will apply. The version of the method overridden in, or inherited into, the class from which the object wasinstantiated will be identified and executed.

Questions & Answers

Inflation is defined as the rise in price of a commodity.
Nureni Reply
It is defined as the rise in price of a commodity.
Nureni
the persistent rise in the prices of goods and services. or commodities.
SULEIMAN
pls the third and fourth law of supply
Yarouh
what's GDP?
Allen
gross domestic product
Annor
GDP stands for Gross Domestic Product
Sande
yes
HlobisileM
what us maxima and minima
MiXUP Reply
Maxima s below equilibrium. Whilst minima s above. Equilibrium
Afran
Wht is demand
Afran
is the willingness and the ability of a consumer to purchase goods at a given price and at a particular point in time.
Assan
Ohhk different question? Ask
Afran
why is the demand curve downwards sloppy?
Assan
3 Reasons.. 1... diminishing marginal utility 2... substitution effect 3...income effect
Harshita
thanks
Assan
Because of the negative or inverse relationship between price and quantity demanded
Afran
what is the law of diminishing returns states?
Assan
ohk
Assan
The law states that all other things being equall as much of variable factor(labour) is employed on fixed factor(land) the marginal product rises..attain a maximum and begins to fall.
Afran
What is income elasticity of demand
Afran
what is monetary policy
Edward
Monetary policy is an attempt to influence the economy by opera ting in such monetary variables
Afran
thanks
Edward
Wlcm
Afran
Wht is disutility?
Afran
is disutility? is rightly writing?
Yhlas
is it i wanna say
Yhlas
Yes please Disutility
Afran
what is macro economics?
Oyas
the branch of economics concerned with large-scale or general economic factors, such as interest rates and national productivity.
idk
in other words it is the study of the economic as a whole
idk
What is an Economic growth
Ayumo Reply
Economic growth is the process whereby the real per capita income of an economy increases over a long period of time.
Nureni
what is the generally accepted defination of economics and by who
IDY Reply
Economics is defined by Lionel Robbins as a social science which studies human behaviour as a relationship between ends and scarce means which have alternative uses
Tba
Importance of economic
Achike Reply
Helps in decision making
MP
I need like 5 importance
Achike
hi
Physcal
Hey
Muhammad
hellow dear.
juwel
hello
Al-ameen
Hello
MP
it helps an individual in rational decision making process
Assan
Fine and u
Buzabaryaho
how does it make individual in rational dicision making decisions
Annor
if an individual is faced with unlimited wants.
Assan
it also helps an individual in arranging their wants in order of their importance.
Assan
ohk
Annor
ok
Al-ameen
Hello guys
Radah
My name is Radah
Radah
Please what is a scale of preference used for?
Radah
it's use for arranging wants in order of their importance.
Assan
in other words when an individual is faced with unlimited wants,scale of preference would help the individual to select the most important wants.
Assan
Thanks
Radah
welcome
Assan
what is tourism
forgive Reply
Tourism is travel for pleasure or business
Yusuf
It is the commercial organization and operation of holidays and visits to places of interest.
Nureni
who is a price taker?
sam Reply
A price taker is a person or a company who have no control to dictate a prices of a goods or services
Unique
Someone who sets price
Nureni
In the trading world, a price taker is a trader who does not affect the price of the stock if he or she buys or sells shares.
Nureni
A price taker refers to a firm or an individual who sets the price of his good and services based on an external factor. In other words he cannot choose and set a price by himself. An example is a firm operating in perfect competition where prices are set through the price mechanism.
Tba
in a common and suitable sense state the law of diminishing returns
Unique Reply
The higher the satisfaction derived from a particular commodity,the lower the demand for it but that law doesn't match in some instances.
Nureni
state the features of an imperfect competitive market
Naomi
@NURENI instance like wat
Unique
imperfect competitive market involves large number of sellers and buyers price makers selling cost product differentiation free entry and exit of a firms
Unique
is economics a science
Alex Reply
yes. a social science.
Carlos
Yes of cause It uses scientific principles in its research. That is to say, analyzing data, making experiment as well as making deductions and drawing conclusions
Aziz
U can understand the scientific nature of economics by learning about the methods used by Abhijit Banerjee(indian) ,the nobel prize laureate 2019.
Harshita
it is considered as a social science
idk
Hence, economics is a science, a social science many can call it, or more appropriately, a young science
Taha
it can be called social science because of behaviour ,which is unpredictable.There r many theroies in economics which make economics a social science But some economic theories makes it science
Harshita
human behaviour*
Harshita
remember science derives from the root words "to know". With that being said most fields of study can be considered as a science or soft science, for they possess key knowledge to attaining understanding of our world.
Alexander
economics is a science cos it deals with human wants, desire or neads in order to satisfy them
Unique
according comparision of political science economic is science.
Hassan
what's the question?
Nureni Reply
question is answering for something to someone
Suheb
Discuss economics system
Henry Reply
discuss institutional system
Henry
Give 3 at most advantages and disadvantages of economics system and institutional syatem
Henry
Give the features characteristics of market or free enterprise
Henry
The structure of an economy is largely determined by the economic system which is a function of the economic ideology of the nation
Nureni
The economic system is grouped into 5 groups: 1: Pure market 2: Developed market 3: Centrally planned or Socialist 4: Mixed market and 5: Market Socialist Economic systems
Nureni
what is inflation
Prince Reply
Inflation is a sustained and general rise in the price of all goods and services of an economy
Tba
hello everyone , I'm New here, third degree price discrimination?
Saeed Reply
2nd degree price discrimination?
Saeed
hi
Kini
hi
Mitchel
Hi
MP
price paid by consumers after the sales tax is called?
Pinias Reply
why government impose price floor on certain products?
Pinias
how can black market be occurred when price ceiling is introduced?
Pinias
How can inflation affect goods and services?
Ph
When prices rise for energy, food, commodities, and other goods and services, the entire economy is affected
Joan
If inflation becomes too high the economy can suffer conversely, if inflation is controlled and at reasonable levels, the economy may prosper. With controlled, lower inflation, employment increases.
Joan
Is it necessary to make decision when it fails you
Evelin Reply
Pls when what fails u
MP
I think so
Kini
well i might naught know what you on about but i gotta tell you, it is necessary
Troy
yep
Ibe
Kk
MP
yep
Ibe
good afternoon guy my name is sneh these any of you can do mathematics
HlobisileM
help me
HlobisileM
Yes I do
Sande
What help can we offer you.
Wahab
in analytical geometry
HlobisileM
chapter
HlobisileM
how to get the coordinates
HlobisileM
hello guys am Abdulai how is everyone doing
Abdulai
good evening guys
Alex
a(1,:3)b(t,0)c(p,-4)and corrdinate p
HlobisileM
pls send e mathematics question
Nti
it has a drawing i can not send photos
HlobisileM
can u hv e pic n send it
Nti
yesl
kafui
how you send a photo
HlobisileM
hello guys how are u all doing am Belinda
kafui
welcome Doh
Michael
Tnx
kafui
Difference between extinct and extici spicies
Amanpreet Reply
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Source:  OpenStax, Object-oriented programming (oop) with java. OpenStax CNX. Jun 29, 2016 Download for free at https://legacy.cnx.org/content/col11441/1.201
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