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Writing your own methods

As mentioned earlier, you can write your own methods in Java. I mention this here so you will know that it is possible. I will have more to say about writing your own methods in futuremodules.

Sample program

A complete listing of a sample program named SqRt01.java is provided in Listing 5 near the end of the lesson. A batch file that you can use to compile and run the program is provided in Listing 6 .

When you compile and run the program, the following output should appear on your computer screen:

5.049752469181039 6.0

As you will see shortly, these are the square root values respectively for 25.5 and 36.

Interesting code fragments

I will explain portions of this program in fragments. I will explain only those portions of the program that are germane to this module. Don't worry about the other details of the program. You will learn about those details infuture modules.

You may find it useful to open this lesson in another browser window so that you can easily scroll back and forth among the fragments while reading the discussion.

The first code fragment that I will explain is shown in Listing 1 .

Listing 1 . The price of beans.
double beans; beans = 25.5;

What is the price of beans?

The code fragment shown in Listing 1 declares a variable named beans and assigns a value of 25.5 to the variable. (I briefly discussed the declaration of variables in a previous module. I will discuss them in more detail in a future module.)

What is that double thing?

In an earlier module, I declared a variable with a type named int . At that time, I explained that only integer values could be stored in that variable.

The variable named beans in Listing 1 is declared to be of the type double . I will explain the concept of data types in detail in a future module. Briefly, double means that you can store any numeric value in this variable, with or without adecimal part. In other words, you can store a value of 3 or a value of 3.33 in this variable, whereas a variable with a declared type of int won't accept a value of 3.33.

Every method has a name

Every method, every variable, and some other things as well have names. The names in Java are case sensitive . By case sensitive, I mean that the method named amethod is not the same as the method named aMethod .

A few words about names in Java

There are several rules that define the format of allowable names in Java. You can dig into this in more detail on the web if you like, but if you followthese two rules, you will be okay:

  • Use only letters and numbers in Java names.
  • Always make the first character a letter.

A standard method named sqrt

Java provides a Math library that contains many standard methods. Included in those methods is a method named sqrt that will calculate and return the square root of a number that is passed as a parameter when the method iscalled.

The sqrt method is called on the right-hand side of the equal sign (=) in the code fragment in Listing 2 .

Listing 2 . Compute the square root of the price of beans.
double sqRtBns = Math.sqrt(beans);

Questions & Answers

Do somebody tell me a best nano engineering book for beginners?
s. Reply
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
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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