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public static final double PI

The double value that is closer than any other to pi, the ratio of the circumference of a circle to its diameter.

The constant named PI

You may recognize the constant named PI from your high school geometry class.

Whenever you need the value for the constant PI , you shouldn't have to instantiate an object just to get access to it. Furthermore, your class shouldnot be required to have any special package relationship with the Math class just to get access to PI .

The good news ...

Because PI is declared to be both public and static in the Math class, it is readily available to any code in any method in any Java program that has access to the standard Java class library.

How is PI accessed?

PI can be accessed by using an expression as simple as that shown below, which consists simply of the name of the class and the name ofthe variable joined by a period (Math.PI) .

double piRSquare = Math.PI * R * R;

No notion of public local variables

As a result of the above, many of you may have become accustomed to associating the keyword public with the keyword final . However, if you missed this question and you have read the explanation to thispoint, you must also remember that there is no notion of public or private for local variables. Therefore, when this program was compiled under JDK 1.3, a compiler error was produced. That compiler error is partiallyreproduced below:

Ap103.java:16: illegal start of expressionpublic final int x = 5;

Back to Question 4

Answer 3

A. Compiler Error

Explanation 3

The final keyword

The final keyword can be applied in a variety of ways in Java. This includes:

  • final parameters
  • final methods
  • final classes
  • final variables (constants)

Behaves like a constant

When the final keyword is applied to a variable in Java, that causes the variable to behave like a constant. In other words, the value of the variablemust be initialized when it is declared, and it cannot be changed thereafter (see the exception discussed below) .

Apply to local or member variables

The final keyword can be applied to either local variables or member variables. (In case you have forgotten, local variables are declared inside a method or constructor, while member variables are declared inside a class, but outside amethod.)

So, what is the problem?

The problem with this program is straightforward. As shown in the following code fragment, after declaring a final local variable and initializing its value to 5, the program attempts to change the value stored in that variable to 10.This is not allowed.

final int x = 5; x = 10;

A compiler error

JDK 1.3 produces the following error message:

Ap102.java:17: cannot assign a value to finalvariable x x = 10;

An interesting twist - blank finals

An interesting twist of the use of the final keyword with local variables is discussed below.

Background information

Regardless of whether or not the local variable is declared final , the compiler will not allow you to access the value in a local variable if thatvariable doesn't contain a value. This means that you must always either initialize a local variable or assign a value to it before you can access it.

Questions & Answers

Application of nanotechnology in medicine
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.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
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
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
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
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
hi
Loga
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit 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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