Revised: Sun Mar 27 20:34:41 CDT 2016
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Table of contents
Preface
General
This module is part of a collection of modules designed to help you learn to program computers.
It explains Java comments.
Prerequisites
In addition to an Internet connection and a browser, you will need the following tools (as a minimum) to work through the exercises in these modules:
- The Sun/Oracle Java Development Kit (JDK) (See (External Link) )
- Documentation for the Sun/Oracle Java Development Kit (JDK) (See (External Link) )
- A simple IDE or text editor for use in writing Java code.
The minimum prerequisites for understanding the material in these modules include:
- An understanding of algebra.
- An understanding of all of the material covered in the earlier modules in this collection.
Viewing tip
I recommend that you open another copy of this document in a separate browser window and use the following links to easily find and view the Figuresand Listings while you are reading about them.
Figures
- Figure 1 . Three styles of comments.
Listings
- Listing 1 . A multi-line comment.
- Listing 2 . Three single-line comments.
- Listing 3 . The program named Comments01.
- Listing 4 . Batch file to compile and run the program named Comments01.
Discussion and sample code
Comments
Producing and using a Java program consists of the following steps:
- Write the source code.
- Compile the source code.
- Execute the program.
The source code consists of a set of instructions that will later be presented to a special program called a compiler for the purpose of producing a program that can be executed. In other words, when you write the source code, you are writing instructions that the compiler will use to produce the executable program.
Some things should be ignored
Sometimes, when you are writing source code, you would like to include information that may be useful to you, but should be ignored by the compiler. Information of that sort is called a comment .
Three styles of comments
Java supports the three styles of comments shown in Figure 1 .
| Figure 1 . Three styles of comments. |
|---|
/** special documentation comment
used by the javadoc tool *//* This is a
multi-line comment *///Single-line comment
program code // Another single-line comment |
The javadoc tool
The javadoc tool mentioned in Figure 1 is a special program that is used to produce documentation for Java programs. Comments of this style begin with /** and end with */ as shown in Figure 1 .
The compiler ignores everything in the source code that begins and ends with this pattern of characters. Documentation produced using the javadoc program is very useful for on-line oron-screen documentation.
Multi-line comments
Multi-line comments begin with /* and end with */ as shown in Figure 1 . As you have probably already guessed, the compiler also ignores everything in the source code that matches this format. (A javadoc comment is simply a multi-line comment insofar as the compiler knows. Only the special program named javadoc.exe cares about javadoc comments.)