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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

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
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
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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