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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

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
okay, so you have 6 raised to the power of 2. what is that part of your answer
I don't understand what the A with approx sign and the boxed x mean
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
I'm not sure why it wrote it the other way
I got X =-6
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
oops. ignore that.
so you not have an equal sign anywhere in the original equation?
is it a question of log
Commplementary angles
Idrissa Reply
im all ears I need to learn
right! what he said ⤴⤴⤴
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
kkk nice
Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
many many of nanotubes
what is the k.e before it land
what is the function of carbon nanotubes?
I'm interested in nanotube
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
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
what is system testing
what is the application of nanotechnology?
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
anybody can imagine what will be happen after 100 years from now in nano tech world
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
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
silver nanoparticles could handle the job?
not now but maybe in future only AgNP maybe any other nanomaterials
I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
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
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele 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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