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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

Do somebody tell me a best nano engineering book for beginners?
s. Reply
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Devang Reply
are you nano engineer ?
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
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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.
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Sanket Reply
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Damian Reply
types of nano material
abeetha Reply
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Sravani Reply
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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
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silver nanoparticles could handle the job?
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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.
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