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The public access modifier

A public instance variable can be accessed by any code in any method in any object that can obtain a reference to the object to which thevariable belongs. However, you must first gain access to the object in order to gain access to the variable. Normally you gain access to the object using areference to the object and then gain access to a member of the object such as a variable or method. This is indirection .

The private access modifier

A private instance variable can be accessed by any code in any method that is defined in the class of the object to which the variablebelongs.

The protected access modifier

A protected instance variable can be accessed by the same methods that can access a private instance variable plus methods in subclasses of the class of the object to which the instance variablebelongs.

I'm not going to try to explain the scope of internal and protected internal instance variables for the reasons that I discussed earlier.

Local variables

A local variable is declared inside a method or constructor. The lifetime of a local variable is limited to the time that control remains within the block ofcode in which the variable is declared. The scope of the variable is limited to the code block in which it is declared and then only to the statements followingthe declaration statement.

Class variables

A class variable belongs to a static class. I believe that the lifetime of a class variable is the same as the lifetime of the program in which the class isloaded.

It is not necessary to instantiate an object of the static class in order to access the variable. Assuming that you have access rights to the variable, youcan access it simply by joining the name of the class to the name of the variable using the dot operator.

More bad programming practice

I personally consider it bad programming practice to use class variables in most cases unless the variables are actually constants. However, there are a fewsituations where you have no choice but to use a non-constant class variable.

Reference variables

A reference variable contains a reference to an object or contains null. You typically use the value stored in a reference variable to locate an object inmemory. Once you locate the object, you typically use the dot operator along with the name of a variable or a method to ask the object to do something. Thisis called indirection .

Primitive variables

Primitive variables contain primitive values. No indirection is required to access the primitive value stored in a primitive variable.

An analogy

An analogy that I often use to explain the difference between a reference variable and a primitive variable goes as follows.

A primitive variable is analogous to your wallet.

If you get robbed and the robber takes your wallet, he has your money because the wallet contains your money just like a primitive variable contains aprimitive value.

A reference variable is analogous to your check book.

If the robber takes your checkbook, he doesn't have your money -- not yet anyway. The checkbook doesn't contain your money. Instead, it contains areference to your bank where your money is stored. A reference variable doesn't contain an object; it contains a reference to an object. Furthermore, two ormore reference variables can contain references to the same object but this is usually not a good idea.

Questions & Answers

current economic plans (MDGS) needs
Ajijola Reply
I don't know what is happening
What is economic
Joeali Reply
What is the importance of study economics
Economic is the study of how humans make decisions in face of sacristy
economics is the study of how humans makes decision in the face of scarcity
economics is the study of human behaviour when faced with difficult situation example when goods and services are scarcity.
what is Economic
Dauda Reply
what is 4ps of economic?
thomas Reply
production place Price product
Criticism of elasticity
Siddikur Reply
what is unemployment
Gyamfi Reply
ohk thanks
why is unemployment rapid in the country
I need more explanation
what is unemployment
Munanag Reply
not working
some one who is willing qualified to work but can't find job
Bethel...explain? please
some one who is willing to work but can't find job
Yes true
which one please
unemployment refers to the ability for someone who is capable and willing to work but could not find a job..
some one who not able to find a job
please what is the secret of learning?
What is stock market?
JOHN Reply
explain the various types of cost curve
Ruth Reply
Short-run average fixed cost (SRAFC) Short-run average total cost (SRAC or SRATC) Short-run average variable cost (AVC or SRAVC) Short-run fixed cost (FC or SRFC) Short-run marginal cost (SRMC) Short-run total cost (SRTC)
what's economic development and growth
Popoola Reply
what do you understand by Ceteris Paribus?
Gabriel Reply
the external factor will remained constant, except the price
everything being equal
explain the uses of microeconomics
Nikita Reply
uses of microeconomics
Adam Smith's definition of economics
Sylvia Reply
what is economic deficit
this is a situation whereby a nation's outcome or available resources are not enough to the people thereby causing scarcity
prices of Quality demanded is equal to Quality supplied
it's quantity demand and quantity supplied that's called equilibrium
they deal With prices
define the elasticity
explain different types of elasticity
oops 😬 you are right you talk about quality I tell about quantity
elasticity is the measurement of the percentage change of one economic variable in response to a change in another
Cross Elasticity of Demand (XED) Income Elasticity of Demand (YED) Price Elasticity of Supply (PES)
anything else?
I need to know everything about theory of consumer behavior
Romy, what is microeconomic?
What is Economic please
Thomas, microeconomics is the study of how consumers, workers, and firms interact to generate outcomes in specific markets
Dauda, economics is the study of people and choices. it is on one side the study of wealth and on the more important side, a part of the study if man
How does one analyze a market where both demand and supply shift?
Gabriel Reply
That's equilibrium market
but an equlibrum can appear twice on the same market... both in Movement along the Demand/supply curve of shift in the Curve
I Mean on the same curve..
how can consumer surplus be calculated
Difference between extinct and extici spicies
Amanpreet 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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