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The multi-line comment style is particularly useful for creating large blocks of information that should be ignored by the compiler. This style can be used to produce a comment consisting of a single line of text as well. However, the single-line comment style discussed in the next section requires less typing.

Single-line comments

Single-line comments begin with // and end at the end of the line. The compiler ignores the // and everything following the slash characters to the end of the line.

This style is particularly useful for inserting short comments throughout the source code. In this case, the // can appear at the beginning of the line as shown in Figure 1 , or can appear anywhere in the line, including at the end of some valid source code (also shown in Figure 1 ) .

Sample program

The purpose of the program named Comments01 , which is shown in Listing 3 near the end of the module, is to illustrate the use of single and multi-line comments. The program does not contain any javadoc comments.

The commands for a batch file that you can use to compile and run this program are provided in Listing 4 .

When you compile and run the program, the following text should appear on your command-line screen:

Hello World

Interesting code fragments

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

A multi-line comment

Listing 1 , shows a multi-line comment, which consists of three lines of text.

As required, this multi-line comment begins with /* and ends with */. The extra stars on the third line are simply part of the comment.

You will often see formats similar to this being used to provide a visual separation between multi-line comments and the other parts of a program.

Listing 1 . A multi-line comment.
/*File Comments01.java This is a multi-line comment.*****************************************/

Single-line comments

Listing 2 shows three single-line comments. Can you spot them? Remember, single-line comments beginwith //.

Listing 2 . Three single-line comments.
class Comments01 { //This is a single-line commentpublic static void main(String[] args){System.out.println("Hello World"); }//end main}//End class

One of the comments in Listing 2 starts at the beginning of the line. The other two comments follow some program code.

Run the program

I encourage you to run the program that I presented in this lesson to confirm that you get the same results. Experiment withthe code, making changes, and observing the results of your changes. Make certain that you can explain why your changes behave as they do.

Complete program listings

Listing 3 contains a complete listing of the program named Comments01 .

Listing 3 . The program named Comments01.
/*File Comments01.java This is a multi-line comment.*****************************************/ class Comments01 {//This is a single-line comment public static void main(String[]args){ System.out.println("Hello World");}//end main }//End class

Listing 4 contains the commands for a batch file that can be used to compile and run the program named Comments01 .

Listing 4 . Batch file to compile and run the program named Comments01.
echo off clsdel *.class javac -cp .; Comments01.javajava -cp .; Comments01 pause


This section contains a variety of miscellaneous information.

Housekeeping material
  • Module name: JJb0140: Java OOP: Java comments
  • File: Jb0140.htm
  • Published: 11/16/12

Financial : Although the Connexions site makes it possible for you to download a PDFfile for this module at no charge, and also makes it possible for you to purchase a pre-printed version of the PDF file, you should be aware thatsome of the HTML elements in this module may not translate well into PDF.

I also want you to know that, I receive no financial compensation from the Connexions website even if you purchase the PDF version of the module.

In the past, unknown individuals have copied my modules from cnx.org, converted them to Kindle books, and placed them for sale on Amazon.comshowing me as the author. I neither receive compensation for those sales nor do I know who does receive compensation. If you purchase such a book, pleasebe aware that it is a copy of a module that is freely available on cnx.org and that it was made and published without my prior knowledge.

Affiliation : I am a professor of Computer Information Technology at Austin Community College in Austin, TX.


Questions & Answers

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 to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
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.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
what is biological synthesis of nanoparticles
Sanket Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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