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Program output

The output produced by compiling and running this program is shown in Figure 1 . The second line of text in Figure 1 ending with the # characterwas typed by the user.

Figure 1 . Screen output from the program named simple1.
Enter some text, terminate with # abcde#The char before the # was e

Discussion of the simple1 program

Purpose

I will use the program shown in Listing 1 to discuss several important aspects of the structure of a Java program. I will also providetwo additional sample programs that illustrate specific points not illustrated in the above program later in this module.

Variables

What is a variable?

Variables are used in a Java program to contain data that changes during the execution of the program.

Declaring a variable

To use a variable, you must first notify the compiler of the name and the type of the variable. This is known as declaring a variable .

The syntax for declaring a variable is to precede the name of the variable with the name of the type of the variable as shown in Listing 2 . It is also possible (but not always required) to initialize a variable in Java when it is declared as shown in Listing 2 .

Listing 2 . Declaring and initializing two variables named ch1 and ch2.
int ch1, ch2 = '0';

The statement in Listing 2 declares two variables of type int , initializing the second variable (ch2) to the value of the zero character (0). (Note that I didn't say initialized to the value zero.)

Difference between zero and '0' - Unicode characters

The value of the zero character is not the same as the numeric value of zero, but hopefully you already knew that.

As an aside, characters in Java are 16-bit entities called Unicode characters instead of 8-bit entities as is the case with many programming languages. The purpose is to provide many more possible characters including characters used in alphabets other than the one used in the United States.

Initialization of the variable

Initialization of the variable named ch2 in this case was necessary to prevent a compiler error. Without initialization of this variable,the compiler would recognize and balk at the possibility that an attempt might be made to execute the statement shown in Listing 3 with a variable named ch2 that had not been initialized

Listing 3 . Display the character.
System.out.println("The char before the # was " + (char)ch2);

Error checking by the compiler

The strong error-checking capability of the Java compiler would refuse to compile this program until that possibility was eliminated by initializing thevariable.

Using the cast operator

You should also note that the contents of the variable ch2 is being cast as type char in Listing 3 .

(A cast is used to change the type of something to a different type.)

Recall that ch2 is a variable of type int , containing the numeric value that represents a character.

We want to display the character that the numeric value represents and not the numeric value itself. Therefore, we must cast it (purposely change its type for the evaluation of the expression) . Otherwise, we would not see the character on the screen. Rather, we would see the numeric value that representsthat character.

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
Abhi
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?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
🤔.
Abhi
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
right! what he said ⤴⤴⤴
Tamia
hii
Uday
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?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
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
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
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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