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Java Language Basics

Comments

Languages Focus

Commenting code generally has three purposes: to document your code, for psuedo coding prior to coding, and to embed compiler directives. Most languages support both a single line comment and a multiple line comment. Some languages also use comments to give instructions to the compiler or interpreter.

Java:   // or /* ... */

Commenting Code
Java uses "//" for a single line comment and /* */ for a multiple line comment.

Syntax Example:
//Single line comment in MS (not ANSI compliant so do NOT use).
/* ANSI compliant single line comment. */
/*
Multiple line
comment.
*/
/*
* This is another popular way 
* to write multi-line comments.
*/




Cross Reference Examples:

Access VBA:   ' or REM

Commenting Code
Access VBA, like all the VB-based languages, uses a single quote (') or the original class-style basic "REM" (most developers just use a quote). Access VBA does NOT have a multiple line comment.

Directives - #

Directives are sometimes called compiler or preprocessor directives. A # is used for directives within Access VBA code. Access VBA offers only an #If..then/#ElseIf/#Else directive.

Syntax Example:
'Single line comment.

REM Old school single line comment.

#If MyDirective Then
'...some code.
#End If
ASP Classic:   ' or REM

Commenting Code
ASP Classic, like all the VB-based languages, uses a single quote (') or the original class-style basic "REM" (most developers just use a quote). ASP Classic does NOT have a multiple line comment.

Preprocessor Directives - @ and #
An @ is used for preprocessor directives within ASP code (within <% %>) and a # is used for HTML-style preprocessor directives.

Note: ASP Classic does not support VB Classic's #If directive.

Syntax Example:
'Single line comment.
REM Old school single line comment.

 

Common Preprocessor Directives include:

<%@LANGUAGE=VBScript%>
<!-- #Include File="includes.inc" -->
C#:  "Multiple Line Comment" // or /* */

Commenting Code
C# uses "//" for a single line comment and /* */ for a multiple line comment.

Syntax Example:
//Single line comment.

/*
Multiple line
comment.
*/
C++:   // or /* ... */

Commenting Code
C++ uses "//" for a single line comment and /* */ for a multiple line comment.

Syntax Example:
//Single line comment in MS (not ANSI compliant so do NOT use).
/* ANSI compliant single line comment. */
/*
Multiple line
comment.
*/
  
/*
* This is another popular
* way to write multi-line
* comments.
*/
C++/CLI:   // or /* ... */

Commenting Code
Same as standard C++. C++ uses "//" for a single line comment and /* */ for a multiple line comment.

Syntax Example:
//Single line comment in MS (not ANSI compliant so do NOT use).
/* ANSI compliant single line comment. */
/*
Multiple line
comment.
*/
  
/*
* This is another popular
* way to write multi-line
* comments.
*/
Corel Paradox:   ; and { ... }

Commenting Code
ObjectPAL uses ; for a single line comment and { } for a multiple line comment.

Syntax Example:  
;Single line comment.

{
Multiple line
comment.
}
Delphi:   // or { ... } or (* ... *)

Commenting Code
Delphi uses // for a single line comment and both {} and (**) for multiple line comments. Although you can nest different types of multiple line comments, it is recommended that you don't.

Compiler Directives - $
A special comment. Delphi compiler directives are in the form of {$DIRECTIVE}. Of interest for comments is using the $IFDEF compiler directive to remark out code.

Syntax Example:
//This is a single line comment.
 
{
Multiple line
comment.
}
 
(*
This too is a
multiple line comment.
*)
 
{$IFDEF TEMPOUT}
//...code here
{$ENDIF}
Delphi Prism:   // or { ... } or (* ... *)

Commenting Code
Delphi uses // for a single line comment and both {} and (**) for multiple line comments. Although you can nest different types of multiple line comments, it is recommended that you don't.

Compiler Directives - $
A special comment. Delphi compiler directives are in the form of {$DIRECTIVE}. Of interest for comments is using the $IFDEF compiler directive to remark out code.

Syntax Example:
//This is a single line comment.
 
{
Multiple line
comment.
}
 
(*
This too is a
multiple line comment.
*)
 
{$IFDEF TEMPOUT}
//...code here
{$ENDIF}
JavaScript:   // or /* ... */

Commenting Code
JavaScript uses "//" for a single line comment and /* */ for a multiple line comment.

Syntax Example:
//This is a single line comment.

/*
Multiple line
comment.
*/
Perl:   #

Commenting Code
Perl uses # for single line comments and Perl does NOT have a multiple line comment.

Compiler Directives (A special comment.)

Perl also uses compiler directives embedded in comments with #! as in:

#!/usr/local/bin/perl -w
Syntax Example:
#This is a comment in Perl.
PHP:   # or // or /* ... */

Commenting Code
Use the multi-line to comment out large blocks of code and to write multiple line comments.

Syntax Example:
#This is a comment in PHP.

//This is too!

/*
This is a multi-line
comment.
*/
VB Classic:   ' or REM

Commenting Code
VB Classic, like all the VB-based languages, uses a single quote (') or the original class-style basic "REM" (most developers just use a quote). VB Classic does NOT have a multiple line comment.

Directives - #

Directives are sometimes called compiler or preprocessor directives. A # is used for directives within VB Classic code. VB Classic offers only an #If..then/#ElseIf/#Else directive.

Syntax Example:
'Single line comment.

REM Old school single line comment.

#If MyDirective Then
'...some code.
#End If

 

VB.Net:   ' or REM

Commenting Code
VB.Net, like all the VB-based languages, uses a single quote (') or the original class-style basic "REM" (most developers just use a quote). VB.Net does NOT have a multiple line comment.

Syntax Example:
'Single line comment.

REM Old school single line comment.

 






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