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词条 Javadoc
释义

  1. History

  2. Technical architecture

      Structure of a Javadoc comment    Overview of Javadoc    Table of Javadoc tags    Examples  

  3. See also

  4. References

  5. External links

{{manual|date=May 2018}}Javadoc (originally cased JavaDoc)[1] is a documentation generator created by Sun Microsystems for the Java language (now owned by Oracle Corporation) for generating API documentation in HTML format from Java source code. The HTML format is used for adding the convenience of being able to hyperlink related documents together.[2]

The "doc comments" format[3] used by Javadoc is the de facto industry standard for documenting Java classes. Some IDEs,[4] like IntelliJ IDEA, NetBeans and Eclipse, automatically generate Javadoc HTML. Many file editors assist the user in producing Javadoc source and use the Javadoc info as internal references for the programmer.

Javadoc also provides an API for creating doclets and taglets, which allows users to analyze the structure of a Java application. This is how JDiff can generate reports of what changed between two versions of an API.

Javadoc does not affect performance in Java as all comments are removed at compilation time. Writing comments and Javadoc is for better understanding the code and thus better maintaining it.

History

Javadoc was an early Java language documentation generator.[5] Prior to the use of documentation generators it was customary to use technical writers who would typically write only standalone documentation for the software,[6] but it was much harder to keep this documentation in sync with the software itself.

Javadoc has been used by Java since the first release, and is usually updated upon every new release of the Java Development Kit.

Technical architecture

Structure of a Javadoc comment

A Javadoc comment is set off from code by standard multi-line comment tags /* and */. The opening tag (called begin-comment delimiter), has an extra asterisk, as in /**.

  1. The first paragraph is a description of the method documented.
  2. Following the description are a varying number of descriptive tags, signifying:
    1. The parameters of the method (@param)
    2. What the method returns (@return)
    3. Any exceptions the method may throw (@throws)
    4. Other less-common tags such as @see (a "see also" tag)

Overview of Javadoc

The basic structure of writing document comments is to embed them inside

/** ... */. The Javadoc is written next to the items

without any separating newline. Note that any import statements must precede the class declaration. The class declaration usually

contains:

// import statements

/**

 * @author      Firstname Lastname 
 * @version     1.6                 (current version number of program) * @since       1.2          (the version of the package this class was first added to) */

public class Test {

}

For methods there is (1) a short, concise, one line description to

explain what the item does. This is followed by (2) a longer

description that may span multiple paragraphs. The details

can be explained in full here. This section is

optional. Lastly, there is (3) a tag section to list the accepted input

arguments and return values of the method. Note that all of the

Javadoc is treated as HTML so the multiple paragraph sections

are separated by a "<p>" paragraph break tag.

/**

 * Short one line description.                           (1) * 
 * Longer description. If there were any, it would be    (2) * here. * 
 * And even more explanations to follow in consecutive * paragraphs separated by HTML paragraph breaks. * * @param  variable Description text text text.          (3) * @return Description text text text. */

public int methodName (...) {

}

Variables are documented similarly to methods with the exception that

part (3) is omitted. Here the variable contains only the short

description:

/**

 * Description of the variable here. */

private int debug = 0;

Note that it is not recommended[7] to define multiple variables in a single documentation comment. This is because Javadoc reads each variable and places them separately to the generated HTML page with the same documentation comment that is copied for all fields.

/**

 * The horizontal and vertical distances of point (x,y) */

public int x, y; // AVOID

Instead, it is recommended to write and document each variable separately:

/**

 * The horizontal distances of point. */

public int x;

/**

 * The vertical distances of point. */

public int y;

Table of Javadoc tags

Some of the available Javadoc tags[8] are listed in the table below:

Tag & ParameterUsageApplies toSince
@author John Smith Describes an author. Class, Interface, Enum
{@docRoot}Represents the relative path to the generated document's root directory from any generated page.Class, Interface, Enum, Field, Method
@version version Provides software version entry. Max one per Class or Interface. Class, Interface, Enum
@since since-text Describes when this functionality has first existed. Class, Interface, Enum, Field, Method
@see reference Provides a link to other element of documentation. Class, Interface, Enum, Field, Method
@param name description Describes a method parameter. Method
@return description Describes the return value. Method
@exception classname description
@throws classname description		 Describes an exception that may be thrown from this method. Method
@deprecated description Describes an outdated method. Class, Interface, Enum, Field, Method
{@inheritDoc}Copies the description from the overridden method.Overriding Method1.4.0
{@link reference}Link to other symbol.Class, Interface, Enum, Field, Method
{@linkplain reference}Identical to {@link}, except the link's label is displayed in plain text than code font.Class, Interface, Enum, Field, Method
{@value #STATIC_FIELD} Return the value of a static field.Static Field1.4.0
{@code literal} Formats literal text in the code font. It is equivalent to <code>{@literal}</code>. Class, Interface, Enum, Field, Method1.5.0
{@literal literal} Denotes literal text. The enclosed text is interpreted as not containing HTML markup or nested javadoc tags. Class, Interface, Enum, Field, Method1.5.0
{@serial literal}Used in the doc comment for a default serializable field.Field
{@serialData literal}Documents the data written by the writeObject( ) or writeExternal( ) methods.Field, Method
{@serialField literal}Documents an ObjectStreamField component.Field

Examples

An example of Javadoc to document a method follows. Notice that spacing and number of characters in this example are as conventions state.

/**

 * Validates a chess move. * * 
Use {@link #doMove(int theFromFile, int theFromRank, int theToFile, int theToRank)} to move a piece. * * @param theFromFile file from which a piece is being moved * @param theFromRank rank from which a piece is being moved * @param theToFile   file to which a piece is being moved * @param theToRank   rank to which a piece is being moved * @return            true if the move is valid, otherwise false * @since             1.0 */

boolean isValidMove(int theFromFile, int theFromRank, int theToFile, int theToRank) {

}

/**

 * Moves a chess piece. * * @see java.math.RoundingMode */

void doMove(int theFromFile, int theFromRank, int theToFile, int theToRank) {

}

See also

  • Comparison of documentation generators
  • .NET XML documentation comments

References

1. ^Now cased as 'Javadoc'. See  . Originally cased as 'JavaDoc'. See  
2. ^https://web.archive.org/web/20170613233020/http://agile.csc.ncsu.edu/SEMaterials/tutorials/javadoc/
3. ^{{cite web|url = http://docs.oracle.com/javase/1.5.0/docs/tooldocs/solaris/javadoc.html|title = javadoc - The Java API Documentation Generator|accessdate = 2011-09-30|publisher = Sun Microsystems}}.
4. ^[https://www.jetbrains.com/idea/ IntelliJ IDEA], NetBeans and Eclipse
5. ^{{cite web|url = http://www.oracle.com/technetwork/java/javase/documentation/index-137868.html|title = How to Write Doc Comments for the Javadoc Tool|accessdate = 2011-09-30|publisher = Sun Microsystems}}.
6. ^{{cite web|url=http://www.artima.com/intv/jackpot3.html |title=Visualizing with JavaDoc |author=Bill Venners, James Gosling....|publisher=artima.com|date=2003-07-08|accessdate=2013-01-19|quote=When I did the original JavaDoc in the original compiler, even the people close around me pretty soundly criticized it. And it was interesting, because the usual criticism was: a good tech writer could do a lot better job than the JavaDoc does. And the answer is, well, yeah, but how many APIs are actually documented by good tech writers? And how many of them actually update their documentation often enough to be useful?}}
7. ^{{cite news|title=Java Platform, Standard Edition Tools Reference for Oracle JDK on Solaris, Linux, and OS X, Release 8. Section "Multiple-Field Declarations"|url=https://docs.oracle.com/javase/8/docs/technotes/tools/unix/javadoc.html#JSSOR650|accessdate=20 Dec 2017}}
8. ^[https://docs.oracle.com/javase/8/docs/technotes/tools/unix/javadoc.html#CHDBEFIF Javadoc tags in JavaSE 6]

External links

  • [https://docs.oracle.com/javase/9/javadoc/javadoc.htm Java Platform, Standard Edition Javadoc Guide]
  • [https://www.jcp.org/en/jsr/detail?id=260 JSR 260] Javadoc Tag Technology Update Java Specification Request (defines new Javadoc tags)
  • [https://web.archive.org/web/20130927133806/https://today.java.net/pub/a/today/2004/08/26/ashkelon.html Improve on Javadoc with ashkelon]
  • Globaldocs: A viewer to browse multiple Javadocs simultaneously.
  • [https://javadoc.allimant.org/ Various Java documentations converted to Windows Help format]

2 : Free documentation generators|Java development tools
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