javadoc-The Java API Documentation Generator (original) (raw)

Generates HTML pages of API documentation from Java source files. This document contains JavadocTMexamples for Sun Solaris.

CONTENTS

Reference Guide

Reference Guide

SYNOPSIS

**javadoc** [ [options](#options) ] [ packagenames ] [ sourcefilenames ] [ -subpackages pkg1:pkg2:... ] [ [@argfiles](#argumentfiles) ]

Arguments can be in any order. See processing of Source Filesfor details on how the Javadoc tool determines which ".java" files to process.

options

Command-line options, as specified in this document. To see a typical use of javadoc options, see Real-World Example.

packagenames

A series of names of packages, separated by spaces, such as java.lang java.lang.reflect java.awt. You must separately specify each package you want to document. Wildcards are not allowed; use -subpackages for recursion. The Javadoc tool uses -sourcepath to look for these package names. See Example - Documenting One or More Packages

sourcefilenames

A series of source file names, separated by spaces, each of which can begin with a path and contain a wildcard such as asterisk (*). The Javadoc tool will process every file whose name ends with ".java", and whose name, when stripped of that suffix, is actually a legal class name (see Identifiers). Therefore, you can name files with dashes (such as X-Buffer), or other illegal characters, to prevent them from being documented. This is useful for test files and template files The path that precedes the source file name determines where javadoc will look for the file. (The Javadoc tool does not use -sourcepath to look for these source file names.) Relative paths are relative to the current directory, so passing in Button.java is identical to ./Button.java. A source file name with an absolute path and a wildcard, for example, is /home/src/java/awt/Graphics*.java. See Example - Documenting One or More Classes. You can also mix packagenames and sourcefilenames, as in Example - Documenting Both Packages and Classes

-subpackages pkg1:pkg2:...

Generates documentation from source files in the specified packages and recursively in their subpackages. An alternative to supplying packagenames or sourcefilenames.

@argfiles

One or more files that contain a list of Javadoc options, packagenames and sourcefilenames in any order. Wildcards (*) and -J options are not allowed in these files.

DESCRIPTION

The JavadocTM tool parses the declarations and documentation comments in a set of Java source files and produces a corresponding set of HTML pages describing (by default) the public and protected classes, nested classes (but not anonymous inner classes), interfaces, constructors, methods, and fields. You can use it to generate the API (Application Programming Interface) documentation or the implementation documentation for a set of source files.

You can run the Javadoc tool on entire packages,individual source files, or both. When documenting entire packages, you can either use -subpackages for traversing recursively down from a top-level directory, or pass in an explicit list of package names. When documenting individual source files, you pass in a list of source (.java) filenames. Examples are given at the end of this document. How Javadoc processes source files is covered next.

Processing of source files

The Javadoc tool processes files that end in ".java" plus other files described under Source Files. If you run the Javadoc tool by explicitly passing in individual source filenames, you can determine exactly which ".java" files are processed. However, that is not how most developers want to work, as it is simpler to pass in package names. The Javadoc tool can be run three ways without explicitly specifying the source filenames. You can (1) pass in package names, (2) use -subpackages, and (3) use wildcards with source filenames (*.java). In these cases, the Javadoc tool processes a ".java" file only if it fulfills all of the following requirements:

Processing of links - During a run, the Javadoc tool automatically adds cross-reference links to package, class and member names that are being documented as part of that run. Links appear in several places:

Other processing details - The Javadoc tool produces one complete document each time it is run; it cannot do incremental builds -- that is, it cannot modify or _directly_incorporate results from previous runs of the Javadoc tool. However, it can link to results from other runs, as just mentioned.

As implemented, the Javadoc tool requires and relies on the java compiler to do its job. The Javadoc tool calls part of javac to compile the declarations, ignoring the member implementation. It builds a rich internal representation of the classes, including the class hierarchy, and "use" relationships, then generates the HTML from that. The Javadoc tool also picks up user-supplied documentation fromdocumentation comments in the source code.

In fact, the Javadoc tool will run on .java source files that are pure stub files with no method bodies. This means you can write documentation comments and run the Javadoc tool in the earliest stages of design while creating the API, before writing the implementation.

Relying on the compiler ensures that the HTML output corresponds exactly with the actual implementation, which may rely on implicit, rather than explicit, source code. For example, the Javadoc tool documents default constructors (section 8.6.7 of Java Language Specification) that are present in the .class files but not in the source code.

In many cases, the Javadoc tool allows you to generate documentation for source files whose code is incomplete or erroneous. This is a benefit that enables you to generate documentation before all debugging and troubleshooting is done. For example, according to the_Java Language Specification_, a class that contains an abstract method should itself be declared abstract. The Javadoc tool does not check for this, and would proceed without a warning, whereas the javac compiler stops on this error. The Javadoc tool does do some primitive checking of doc comments. Use the DocCheck doclet to check the doc comments more thoroughly.

When the Javadoc tool builds its internal structure for the documentation, it loads all referenced classes. Because of this, the Javadoc tool must be able to find all referenced classes, whether bootstrap classes, extensions, or user classes. For more about this, see How Classes Are Found. Generally speaking, classes you create must either be loaded as an extension or in the Javadoc tool's class path.

Javadoc Doclets

You can customize the content and format of the Javadoc tool's output by using doclets. The Javadoc tool has a default "built-in" doclet, called the standard doclet, that generates HTML-formatted API documentation. You can modify or subclass the standard doclet, or write your own doclet to generate HTML, XML, MIF, RTF or whatever output format you'd like. Information about doclets and their use is at the following locations:

Terminology

The terms documentation comment, doc comment, main description, tag, block tag, and in-line tag are described atDocumentation Comments. These other terms have specific meanings within the context of the Javadoc tool:

generated document

The document generated by the javadoc tool from the doc comments in Java source code. The default generated document is in HTML and is created by the standard doclet.

name

A name of a program element written in the Java Language -- that is, the name of a package, class, interface, field, constructor or method. A name can be fully-qualified, such as java.lang.String.equals(java.lang.Object), or partially-qualified, such as equals(Object).

documented classes

The classes and interfaces for which detailed documentation is generated during a javadoc run. To be documented, the source files must be available, their source filenames or package names must be passed into the javadoc command, and they must not be filtered out by their access modifier (public, protected, package-private or private). We also refer to these as the classes included in the javadoc output, or the included classes.

included classes

Classes and interfaces whose details are documented during a run of the Javadoc tool. Same as documented classes.

excluded classes

Classes and interfaces whose details are not documented during a run of the Javadoc tool.

referenced classes

The classes and interfaces that are explicitly referred to in the definition (implementation) or doc comments of the documented classes and interfaces. Examples of references include return type, parameter type, cast type, extended class, implemented interface, imported classes, classes used in method bodies, @see, {@link}, {@linkplain}, and {@inheritDoc} tags. (Notice this definition has changed since 1.3.) When the Javadoc tool is run, it should load into memory all of the referenced classes in javadoc's bootclasspath and classpath. (The Javadoc tool prints a "Class not found" warning for referenced classes not found.) The Javadoc tool can derive enough information from the .class files to determine their existence and the fully-qualified names of their members.

external referenced classes

The referenced classes whose documentation is not being generated during a javadoc run. In other words, these classes are not passed into the Javadoc tool on the command line. Links in the generated documentation to those classes are said to be external references or external links. For example, if you run the Javadoc tool on only the java.awt package, then any class in java.lang, such as Object, is an external referenced class. External referenced classes can be linked to using the -link and -linkoffline options. An important property of an external referenced class is that its source comments are normally not available to the Javadoc run. In this case, these comments cannot be inherited.

SOURCE FILES

The Javadoc tool will generate output originating from four different types of "source" files: Java language source files for classes (.java), package comment files, overview comment files, and miscellaneous unprocessed files. This section also covers test files and template files that can also be in the source tree, but which you want to be sure not to document.

Class Source Code Files

Each class or interface and its members can have their own documentation comments, contained in a .java file. For more details about these doc comments, seeDocumentation Comments.

Package Comment Files

Each package can have its own documentation comment, contained in its own "source" file, that the Javadoc tool will merge into the package summary page that it generates. You typically include in this comment any documentation that applies to the entire package.

To create a package comment file, you have a choice of two files to place your comments:

**package-info.java** This file can contain a package comment of the following structure -- the comment is placed before the package declaration:

File: java/applet/package-info.java

/**

Note that while the comment separators /** and /*must be present, the leading asteriskson the intermediate lines can be omitted.**package.html** - This file can contain a package comment of the following structure -- the comment is placed in the <body> element:

File: java/applet/package.html

Provides the classes necessary to create an applet and the classes an applet uses to communicate with its applet context.

The applet framework involves two entities: the applet and the applet context. An applet is an embeddable window (see the {@link java.awt.Panel} class) with a few extra methods that the applet context can use to initialize, start, and stop the applet.

@since 1.0 @see java.awt

Notice this is just a normal HTML file and does not include a package declaration. The content of the package comment file is written in HTML, like all other comments, with one exception: The documentation comment should not include the comment separators /** and */ or leading asterisks. When writing the comment, you should make the first sentence a summary about the package, and not put a title or any other text between<body> and the first sentence. You can include package tags; as with any documentation comment, all block tags must appear after the main description. If you add a @see tag in a package comment file, it must have a fully-qualified name. For more details, see the example of package.html.

Processing of package comment file - When the Javadoc tool runs, it will automatically look for the package comment file; if found, the Javadoc tool does the following:

Overview Comment File

Each application or set of packages that you are documenting can have its own overview documentation comment, kept in its own "source" file, that the Javadoc tool will merge into the overview page that it generates. You typically include in this comment any documentation that applies to the entire application or set of packages.

To create an overview comment file, you can name the file anything you want, typically overview.html and place it anywhere, typically at the top level of the source tree. For example, if the source files for the java.applet package are contained in /home/user/src/java/applet directory, you could create an overview comment file at/home/user/src/overview.html.

Notice you can have multiple overview comment files for the same set of source files, in case you want to run javadoc multiple times on different sets of packages. For example, you could run javadoc once with -private for internal documentation and again without that option for public documentation. In this case, you could describe the documentation as public or internal in the first sentence of each overview comment file.

The content of the overview comment file is one big documentation comment, written in HTML, like the package comment file described previously. See that description for details. To re-iterate, when writing the comment, you should make the first sentence a summary about the application or set of packages, and not put a title or any other text between <body> and the first sentence. You can include overview tags; as with any documentation comment, all tags except in-line tags, such as {@link}, must appear after the main description. If you add a @see tag, it must have a fully-qualified name.

When you run the Javadoc tool, you specify the overview comment file name with the -overview option. The file is then processed similar to that of a package comment file.

Miscellaneous Unprocessed Files

You can also include in your source any miscellaneous files that you want the Javadoc tool to copy to the destination directory. These typically includes graphic files, example Java source (.java) and class (.class) files, and self-standing HTML files whose content would overwhelm the documentation comment of a normal Java source file.

To include unprocessed files, put them in a directory called**doc-files** which can be a subdirectory of any package directory that contains source files. You can have one such subdirectory for each package. You might include images, example code, source files, .class files, applets and HTML files. For example, if you want to include the image of a buttonbutton.gif in the java.awt.Button class documentation, you place that file in the/home/user/src/java/awt/doc-files/ directory. Notice the doc-files directory should not be located at/home/user/src/java/doc-files because java is not a package -- that is, it does not directly contain any source files.

All links to these unprocessed files must be hard-coded, because the Javadoc tool does not look at the files -- it simply copies the directory and all its contents to the destination. For example, the link in the Button.java doc comment might look like:

/** * This button looks like this: * */

Test Files and Template Files

Some developers have indicated they want to store test files and templates files in the source tree near their corresponding source files. That is, they would like to put them in the same directory, or a subdirectory, of those source files.

If you run the Javadoc tool by explicitly passing in individual source filenames, you can deliberately omit test and templates files and prevent them from being processed. However, if you are passing in package names or wildcards, you need to follow certain rules to ensure these test files and templates files are not processed.

Test files differ from template files in that the former are legal, compilable source files, while the latter are not, but may end with ".java".

Test files - Often developers want to put compilable, runnable test files for a given package in the same directory as the source files for that package. But they want the test files to belong to a package other than the source file package, such as the unnamed package (so the test files have no package statement or a different package statement from the source). In this scenario, when the source is being documented by specifying its package name specified on the command line, the test files will cause warnings or errors. You need to put such test files in a subdirectory. For example, if you want to add test files for source files in com.package1, put them in a subdirectory that would be an invalid package name (because it contains a hyphen):

com/package1/test-files/

The test directory will be skipped by the Javadoc tool with no warnings.

If your test files contain doc comments, you can set up a separate run of the Javadoc tool to produce documentation of the test files by passing in their test source filenames with wildcards, such as com/package1/test-files/*.java.

Templates for source files - Template files have names that often end in ".java" and are not compilable. If you have a template for a source file that you want to keep in the source directory, you can name it with a dash (such as Buffer-Template.java), or any other illegal Java character, to prevent it from being processed. This relies on the fact that the Javadoc tool will only process source files whose name, when stripped of the ".java" suffix, is actually a legal class name (see Identifiers).

GENERATED FILES

By default, javadoc uses a standard doclet that generates HTML-formatted documentation. This doclet generates the following kinds of files (where each HTML "page" corresponds to a separate file). Note that javadoc generates files with two types of names: those named after classes/interfaces, and those that are not (such as package-summary.html). Files in the latter group contain hyphens to prevent filename conflicts with those in the former group.

Basic Content Pages

Cross-Reference Pages

Support Files

HTML Frames

The Javadoc tool will generate either two or three HTML frames, as shown in the figure below. It creates the minimum necessary number of frames by omitting the list of packages if there is only one package (or no packages). That is, when you pass a single package name or source files (*.java) belonging to a single package as arguments into the javadoc command, it will create only one frame (C) in the left-hand column -- the list of classes. When you pass into javadoc two or more package names, it creates a third frame (P) listing all packages, as well as an overview page (Detail). This overview page has the filename overview-summary.html. Thus, this file is created only if you pass in two or more package names. You can bypass frames by clicking on the "No Frames" link or entering at overview-summary.html.

If you are unfamiliar with HTML frames, you should be aware that frames can have focus for printing and scrolling. To give a frame focus, click on it. Then on many browsers the arrow keys and page keys will scroll that frame, and the print menu command will print it.

         ------------                  ------------
         |C| Detail |                  |P| Detail |
         | |        |                  | |        |
         | |        |                  |-|        |
         | |        |                  |C|        |
         | |        |                  | |        |
         | |        |                  | |        |
         ------------                  ------------
        javadoc *.java           javadoc java.lang java.awt

Load one of the following two files as the starting page depending on whether you want HTML frames or not:

The generated class and interface files are organized in the same directory hierarchy that Java source files and class files are organized. This structure is one directory per subpackage.

For example, the document generated for the class java.applet.Applet class would be located at java/applet/Applet.html. The file structure for the java.applet package follows, given that the destination directory is named apidocs. All files that contain the word "frame" appear in the upper-left or lower-left frames, as noted. All other HTML files appear in the right-hand frame.

NOTE - Directories are shown in bold. The asterisks (*) indicate the files and directories that are omitted when the arguments to javadoc are source filenames (*.java) rather than package names. Also when arguments are source filenames, package-list is created but is empty. The doc-files directory will not be created in the destination unless it exists in the source tree.

apidocs Top directory index.html Initial page that sets up HTML frames

Generated API Declarations

The Javadoc tool generates a declaration at the start of each class, interface, field, constructor, and method description for that API item. For example, the declaration for theBoolean class is:

public final class Boolean extends Object implements Serializable

and the declaration for the Boolean.valueOfmethod is:

public static Boolean valueOf(String s)

The Javadoc tool can include the modifiers public, protected, private, abstract, final, static, transient, and volatile, but not synchronized or native. These last two modifiers are considered implementation detail and not part of the API specification.

Rather than relying on the keyword synchronized, APIs should document their concurrency semantics in the comment's main description, as in "a single Enumeration cannot be used by multiple threads concurrently". The document should not describe how to achieve these semantics. As another example, while Hashtable should be thread-safe, there's no reason to specify that we achieve this by synchronizing all of its exported methods. We should reserve the right to synchronize internally at the bucket level, thus offering higher concurrency.

DOCUMENTATION COMMENTS

The original "Documentation Comment Specification" can be found under related documentation.

Commenting the Source Code

You can include documentation comments ("doc comments") in the source code, ahead of declarations for any class, interface, method, constructor, or field. You can also create doc comments for eachpackage and another one for the overview, though their syntax is slightly different. Doc comments are also known informally as "Javadoc comments" (but this term violates its trademark usage). A doc comment consists of the characters between the characters/** that begin the comment and the characters*/ that end it. Leading asterisks are allowed on each line and are described further below. The text in a comment can continue onto multiple lines.

/**

To save space you can put a comment on one line:

/** This comment takes up only one line. */

Placement of comments - Documentation comments are recognized only when placed immediately before class, interface, constructor, method, or field declarations -- see the class example, method example, and field example. Documentation comments placed in the body of a method are ignored. Only one documentation comment per declaration statement is recognized by the Javadoc tool.

A common mistake is to put an import statement between the class comment and the class declaration. Avoid this, as the Javadoc tool will ignore the class comment.

/**

import com.sun; // MISTAKE - Important not to put import statement here

public class Whatever { }

A doc comment is composed of a main description followed by a tag section - The _main description_begins after the starting delimiter /** and continues until the tag section. The tag section starts with the first block tag, which is defined by the first @ character that begins a line (ignoring leading asterisks, white space, and leading separator /**). It is possible to have a comment with only a tag section and no main description. The main description cannot continue after the tag section begins. The argument to a tag can span multiple lines. There can be any number of tags -- some types of tags can be repeated while others cannot. For example, this @see starts the tag section:

/**

Block tags and in-line tags - A tagis a special keyword within a doc comment that the Javadoc tool can process. There are two kinds of tags:block tags, which appear as @tag (also known as "standalone tags"), and in-line tags, which appear within curly braces, as {@tag}. To be interpreted, a block tag must appear at the beginning of a line, ignoring leading asterisks, white space, and separator (/**). This means you can use the @ character elsewhere in the text and it will not be interpreted as the start of a tag. If you want to start a line with the @ character and not have it be interpreted, use the HTML entity &#064;. Each block tag has associated text, which includes any text following the tag up to, but not including, either the next tag, or the end of the doc comment. This associated text can span multiple lines. An in-line tag is allowed and interpreted anywhere that text is allowed. The following example contains the block tag @deprecated and in-line tag {@link}.

/**

Comments are written in HTML - The text must be written in HTML, in that they should use HTML entities and can use HTML tags. You can use whichever version of HTML your browser supports; we have written the standard doclet to generate HTML 3.2-compliant code elsewhere (outside of the documentation comments) with the inclusion of cascading style sheets and frames. (We preface each generated file with "HTML 4.0" because of the frame sets.)

For example, entities for the less-than (<) and greater-than (>) symbols should be written &lt; and &gt;. Likewise, the ampersand (&) should be written &amp;. The bold HTML tag <b> is shown in the following example.

Here is a doc comment:

/**

Leading asterisks - When javadoc parses a doc comment, leading asterisk (*) characters on each line are discarded; blanks and tabs preceding the initial asterisk (*) characters are also discarded. Starting with 1.4, if you omit the leading asterisk on a line, the leading white space is no longer removed. This enables you to paste code examples directly into a doc comment inside a <PRE> tag, and its indentation will be honored. Spaces are generally interpreted by browsers more uniformly than tabs. Indentation is relative to the left margin (rather than the separator /** or <PRE> tag).

First sentence - The first sentence of each doc comment should be a summary sentence, containing a concise but complete description of the declared entity. This sentence ends at the first period that is followed by a blank, tab, or line terminator, or at the first block tag. The Javadoc tool copies this first sentence to the member summary at the top of the HTML page.

Declaration with multiple fields - Java allows declaring multiple fields in a single statement, but this statement can have only one documentation comment, which is copied for all fields. Therefore if you want individual documentation comments for each field, you must declare each field in a separate statement. For example, the following documentation comment doesn't make sense written as a single declaration and would be better handled as two declarations:

/**

  • The horizontal and vertical distances of point (x,y) */ public int x, y; // Avoid this

The Javadoc tool generates the following documentation from the above code:

public int x

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

public int y

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

Use header tags carefully - When writing documentation comments for members, it's best not to use HTML heading tags such as

and

, because the Javadoc tool creates an entire structured document and these structural tags might interfere with the formatting of the generated document. However, it is fine to use these headings in class and package comments to provide your own structure.

Automatic Copying of Method Comments

The Javadoc tool has the ability to copy or "inherit" method comments in classes and interfaces under the following two circumstances. Constructors, fields and nested classes do not inherit doc comments.

The source file for the inherited method need only be on the path specified by -sourcepathfor the doc comment to actually be available to copy. Neither the class nor its package needs to be passed in on the command line. This contrasts with 1.3.x and earlier releases, where the class had to be a documented class

Inherit from classes and interfaces - Inheriting of comments occurs in all three possible cases of inheritance from classes and interfaces:

In the first two cases, for method overrides, the Javadoc tool generates a subheading "Overrides" in the documentation for the overriding method, with a link to the method it is overriding, whether or not the comment is inherited.

In the third case, when a method in a given class implements a method in an interface, the Javadoc tool generates a subheading "Specified by" in the documentation for the overriding method, with a link to the method it is implementing. This happens whether or not the comment is inherited.

Algorithm for Inheriting Method Comments - If a method does not have a doc comment, or has an {@inheritDoc} tag, the Javadoc tool searches for an applicable comment using the following algorithm, which is designed to find the most specific applicable doc comment, giving preference to interfaces over superclasses:

  1. Look in each directly implemented (or extended) interface in the order they appear following the word implements (or extends) in the method declaration. Use the first doc comment found for this method.
  2. If step 1 failed to find a doc comment, recursively apply this entire algorithm to each directly implemented (or extended) interface, in the same order they were examined in step 1.
  3. If step 2 failed to find a doc comment and this is a class other than Object (not an interface):
  4. If the superclass has a doc comment for this method, use it.
  5. If step 3a failed to find a doc comment, recursively apply this entire algorithm to the superclass.

JAVADOC TAGS

The Javadoc tool parses special tags when they are embedded within a Java doc comment. These doc tags enable you to autogenerate a complete, well-formatted API from your source code. The tags start with an "at" sign (@) and are case-sensitive -- they must be typed with the uppercase and lowercase letters as shown. A tag must start at the beginning of a line (after any leading spaces and an optional asterisk) or it is treated as normal text. By convention, tags with the same name are grouped together. For example, put all @see tags together.

Tags come in two types:

The current tags are:

Tag Introduced in JDK/SDK
@author 1.0
{@code} 1.5
{@docRoot} 1.3
@deprecated 1.0
@exception 1.0
{@inheritDoc} 1.4
{@link} 1.2
{@linkplain} 1.4
{@literal} 1.5
@param 1.0
@return 1.0
@see 1.0
@serial 1.2
@serialData 1.2
@serialField 1.2
@since 1.1
@throws 1.2
{@value} 1.4
@version 1.0

For custom tags, see the -tag option.

@author name-text

Adds an "Author" entry with the specified name-textto the generated docs when the -author option is used. A doc comment may contain multiple @author tags. You can specify one name per @author tag or multiple names per tag. In the former case, the Javadoc tool inserts a comma (,) and space between names. In the latter case, the entire text is simply copied to the generated document without being parsed. Therefore, you can use multiple names per line if you want a localized name separator other than comma.

For more details, see Where Tags Can Be Used andwriting @author tags.

@deprecated deprecated-text

Note: Starting with JDK 5.0, you can deprecate a program element using the @Deprecated annotation.

Adds a comment indicating that this API should no longer be used (even though it may continue to work). The Javadoc tool moves the deprecated-text ahead of the main description, placing it in italics and preceding it with a bold warning: "Deprecated". This tag is valid in all doc comments: overview, package, class, interface, constructor, method and field.

The first sentence of deprecated-text should at least tell the user when the API was deprecated and what to use as a replacement. The Javadoc tool copies just the first sentence to the summary section and index. Subsequent sentences can also explain why it has been deprecated. You should include a {@link} tag (for Javadoc 1.2 or later) that points to the replacement API:

For more details, seewriting @deprecated tags.

For more about deprecation, see The @deprecated tag.

{@code text**}**

Equivalent to <code>{@literal}</code>.

Displays text in code font without interpreting the text as HTML markup or nested javadoc tags. This enables you to use regular angle brackets (< and >) instead of the HTML entities (&lt; and &gt;) in doc comments, such as in parameter types (<Object>), inequalities (3 < 4), or arrows (<-). For example, the doc comment text:

`{@code A<B>C}`

displays in the generated HTML page unchanged, as:

`A<B>C`

The noteworthy point is that the <B> is not interpreted as bold and is in code font.

If you want the same functionality without the code font, use {@literal}.

{@docRoot}

Represents the relative path to the generated document's (destination) root directory from any generated page. It is useful when you want to include a file, such as a copyright page or company logo, that you want to reference from all generated pages. Linking to the copyright page from the bottom of each page is common.

This {@docRoot} tag can be used both on the command line and in a doc comment: This tag is valid in all doc comments: overview, package, class, interface, constructor, method and field, including the text portion of any tag (such as @return, @param and @deprecated).

  1. On the command line, where the header/footer/bottom are defined:
    javadoc -bottom 'Copyright'
    NOTE - When using {@docRoot} this way in a make file, some makefile programs require special escaping for the brace {} characters. For example, the Inprise MAKE version 5.2 running on Windows requires double braces: {{@docRoot}}. It also requires double (rather than single) quotes to enclose arguments to options such as -bottom (with the quotes around the href argument omitted).
  2. In a doc comment:
    /**
    • See the Copyright.
      */ The reason this tag is needed is because the generated docs are in hierarchical directories, as deep as the number of subpackages. This expression:

would resolve to:

for java/lang/Object.java

and

for java/lang/ref/Reference.java

@exception class-name description

The @exception tag is a synonym for @throws.

{@inheritDoc}

Inherits (copies) documentation from the "nearest" inheritable class or implementable interface into the current doc comment at this tag's location. This allows you to write more general comments higher up the inheritance tree, and to write around the copied text.

This tag is valid only in these places in a doc comment:

See Automatic Copying of Method Comments for a more precise description of how comments are found in the inheritance hierarchy. Note that if this tag is missing, the comment is or is not automatically inherited according to rules described in that section.

{@link package.class#member label**}**

Inserts an in-line link with visible text label that points to the documentation for the specified package, class or member name of a referenced class. This tag is valid in all doc comments: overview, package, class, interface, constructor, method and field, including the text portion of any tag (such as @return, @param and @deprecated).

This tag is very simliar to @see -- both require the same references and accept exactly the same syntax for package.class#memberand label. The main difference is that {@link}generates an in-line link rather than placing the link in the "See Also" section. Also, the {@link} tag begins and ends with curly braces to separate it from the rest of the in-line text. If you need to use "}" inside the label, use the HTML entity notation }

There is no limit to the number of {@link} tags allowed in a sentence. You can use this tag in the main descriptionpart of any documentation comment or in the text portion of any tag (such as @deprecated, @return or @param).

For example, here is a comment that refers to the getComponentAt(int, int) method:

Use the {@link #getComponentAt(int, int) getComponentAt} method.

From this, the standard doclet would generate the following HTML (assuming it refers to another class in the same package):

Use the getComponentAt method.

Which appears on the web page as:

Use the getComponentAt method.

You can extend {@link} to link to classes not being documented by using the -link option.

For more details, seewriting {@link} tags.

{@linkplain package.class#member label**}**

Identical to {@link}, except the link's label is displayed in plain text than code font. Useful when the label is plain text. Example:

Refer to {@linkplain add() the overridden method}.

This would display as:

Refer to the overridden method.

{@literal text**}**

Displays text without interpreting the text as HTML markup or nested javadoc tags. This enables you to use regular angle brackets (< and >) instead of the HTML entities (&lt; and &gt;) in doc comments, such as in parameter types (<Object>), inequalities (3 < 4), or arrows (<-). For example, the doc comment text:

`{@literal A<B>C}`

displays unchanged in the generated HTML page in your browser, as:

``AC

The noteworthy point is that the <B> is not interpreted as bold (and it is not in code font).

If you want the same functionality but with the text in code font, use {@code}.

@param parameter-name description

Adds a parameter with the specified parameter-name followed by the specified description to the "Parameters" section. When writing the doc comment, you may continue the description onto multiple lines. This tag is valid only in a doc comment for a method, constructor or class.

The parameter-name can be the name of a parameter in a method or constructor, or the name of a type parameter of a class, method or constructor. Use angle brackets around this parameter name to specify the use of a type parameter.

Example of a type parameter of a class:

/**
 * @param <E> Type of element stored in a list
 */
public interface List<E> extends Collection<E> {
}

Example of a type parameter of a method:

/**
 * @param string  the string to be converted
 * @param type    the type to convert the string to
 * @param <T>     the type of the element
 * @param <V>     the value of the element
 */
<T, V extends T> V convert(String string, Class<T> type) {
}

For more details, see writing @param tags.

@return description

Adds a "Returns" section with the description text. This text should describe the return type and permissible range of values. This tag is valid only in a doc comment for a method.

For more details, see writing @return tags.

@see reference

Adds a "See Also" heading with a link or text entry that points to reference. A doc comment may contain any number of @see tags, which are all grouped under the same heading. The @see tag has three variations; the third form below is the most common. This tag is valid in any doc comment: overview, package, class, interface, constructor, method or field. For inserting an in-line link within a sentence to a package, class or member, see {@link}.

@see "string"

Adds a text entry for string. No link is generated. The string is a book or other reference to information not available by URL. The Javadoc tool distinguishes this from the previous cases by looking for a double-quote (") as the first character. For example:

@see "The Java Programming Language"

This generates text such as:

See Also:

"The Java Programming Language"

@see <a href="URL#value">label</a>

Adds a link as defined by URL#value. The URL#value is a relative or absolute URL. The Javadoc tool distinguishes this from other cases by looking for a less-than symbol (<) as the first character. For example:

@see <a href="spec.html#section">Java Spec</a>

This generates a link such as:

See Also:

Java Spec

@see package.class#member label

Adds a link, with visible text label, that points to the documentation for the specified name in the Java Language that is referenced. The label is optional; if omitted, the name appears instead as the visible text, suitably shortened -- see How a name is displayed. Use -noqualifier to globally remove the package name from this visible text. Use the label when you want the visible text to be different from the auto-generated visible text.

Only in version 1.2, just the name but not the label would automatically appear in HTML tags, Starting with 1.2.2, the is always included around the visible text, whether or not a label is used.

Example - In this example, an @see tag (in the Characterclass) refers to the equals method in the String class. The tag includes both arguments: the name "String#equals(Object)" and the label "equals".

/**

  • @see String#equals(Object) equals */

The standard doclet produces HTML something like this:

See Also:
equals

Which looks something like this in a browser, where the label is the visible link text:

See Also:

equals

Specifying a name - This package.class#member name can be either fully-qualified, such asjava.lang.String#toUpperCase() or not, such as String#toUpperCase() or #toUpperCase(). If less than fully-qualified, the Javadoc tool uses the normal Java compiler search order to find it, further described below in Search order for @see. The name can contain whitespace within parentheses, such as between method arguments.

Of course the advantage of providing shorter, "partially-qualified" names is that they are shorter to type and there is less clutter in the source code. The following table shows the different forms of the name, where Classcan be a class or interface, Type can be a class, interface, array, or primitive, and method can be a method or constructor.

Typical forms for @see package.class#member
Referencing a member of the current class @see #field @see #method(Type, Type,...) @see #method(Type argname, Type argname,...) @see #constructor(Type, Type,...) @see #constructor(Type argname, Type argname,...) Referencing another class in the current or imported packages @see Class#field @see Class#method(Type, Type,...) @see Class#method(Type argname, Type argname,...) @see Class#constructor(Type, Type,...) @see Class#constructor(Type argname, Type argname,...) @see Class.NestedClass @see Class Referencing an element in another package (fully qualified) @see package.Class#field @see package.Class#method(Type, Type,...) @see package.Class#method(Type argname, Type argname,...) @see package.Class#constructor(Type, Type,...) @see package.Class#constructor(Type argname, Type argname,...) @see package.Class.NestedClass @see package.Class @see package

The following notes apply to the above table:

Search order for @see - the Javadoc tool will process a @see tag that appears in a source file (.java), package file (package.html or package-info.java) or overview file (overview.html). In the latter two files, you must fully-qualify the name you supply with @see. In a source file, you can specify a name that is fully-qualified or partially-qualified.

When the Javadoc tool encounters a @see tag in a .java file that is not fully qualified, it searches for the specified name in the same order as the Java compiler would (except the Javadoc tool will not detect certain namespace ambiguities, since it assumes the source code is free of these errors). This search order is formally defined in Chapter 6, "Names" of the Java Language Specification, Second Edition. The Javadoc tool searches for that name through all related and imported classes and packages. In particular, it searches in this order:

  1. the current class or interface
  2. any enclosing classes and interfaces, searching closest first
  3. any superclasses and superinterfaces, searching closest first
  4. the current package
  5. any imported packages, classes and interfaces, searching in the order of the import statement

The Javadoc tool continues to search recursively through steps 1-3 for each class it encounters until it finds a match. That is, after it searches through the current class and its enclosing class E, it will search through E's superclasses before E's enclosing classes.In steps 4 and 5, the Javadoc tool does not search classes or interfaces within a package in any specified order (that order depends on the particular compiler). In step 5, the Javadoc tool looks in java.lang, since that is automatically imported by all programs.

The Javadoc tool does not necessarily look in subclasses, nor will it look in other packages even if their documentation is being generated in the same run. For example, if the @see tag is in the java.awt.event.KeyEvent class and refers to a name in the java.awt package, javadoc does not look in that package unless that class imports it.

How a name is displayed - If label is omitted, then _package.class.member_appears. In general, it is suitably shortened relative to the current class and package. By "shortened", we mean the Javadoc tool displays only the minimum name necessary. For example, if the String.toUpperCase() method contains references to a member of the same class and to a member of a different class, the class name is displayed only in the latter case, as shown in the following table.

Use -noqualifier to globally remove the package names.

Type of Reference Example in String.toUpperCase() Displays As
@see tag refers to member of the same class, same package @see String#toLowerCase() toLowerCase() (omits the package and class names)
@see tag refers to member of a different class, same package @see Character#toLowerCase(char) Character.toLowerCase(char) (omits the package name, includes the class name)
@see tag refers to member of a different class, different package @see java.io.File#exists() java.io.File.exists() (includes the package and class names)

Examples of @see
The comment to the right shows how the name would be displayed if the@see tag is in a class in another package, such as java.applet.Applet.

                                      See also:

@see java.lang.String // String
@see java.lang.String The String class // The String class
@see String // String
@see String#equals(Object) // String.equals(Object)
@see String#equals // String.equals(java.lang.Object)
@see java.lang.Object#wait(long) // java.lang.Object.wait(long)
@see Character#MAX_RADIX // Character.MAX_RADIX
@see Java Spec // Java Spec
@see "The Java Programming Language" // "The Java Programming Language"

You can extend @see to link to classes not being documented by using the -link option.

For more details, see writing @see tags.

@serial field-description | include | exclude

Used in the doc comment for a default serializable field.

An optional field-description should explain the meaning of the field and list the acceptable values. If needed, the description can span multiple lines. The standard doclet adds this information to the serialized form page.

If a serializable field was added to a class some time after the class was made serializable, a statement should be added to its main description to identify at which version it was added.

The include and exclude arguments identify whether a class or package should be included or excluded from the serialized form page. They work as follows:

Examples: The javax.swing package is marked @serial exclude (in package.html or package-info.java). The public class java.security.BasicPermission is marked @serial exclude. The package-private class java.util.PropertyPermissionCollection is marked @serial include.

The tag @serial at a class level overrides @serial at a package level.

For more information about how to use these tags, along with an example, see "Documenting Serializable Fields and Data for a Class," Section 1.6 of the Java Object Serialization Specification. Also see the Serialization FAQ, which covers common questions, such as "Why do I see javadoc warnings stating that I am missing @serial tags for private fields if I am not running javadoc with the -private switch?". Also see Sun's criteria for including classes in the serialized form specification.

@serialField field-name field-type field-description

Documents an ObjectStreamField component of a Serializable class's serialPersistentFields member. One @serialField tag should be used for each ObjectStreamField component.

@serialData data-description

The data-description documents the types and order of data in the serialized form. Specifically, this data includes the optional data written by the writeObject method and all data (including base classes) written by the Externalizable.writeExternal method.

The @serialData tag can be used in the doc comment for the writeObject, readObject, writeExternal, readExternal,writeReplace, and readResolve methods.

@since since-text

Adds a "Since" heading with the specified since-textto the generated documentation. The text has no special internal structure. This tag is valid in any doc comment: overview, package, class, interface, constructor, method or field. This tag means that this change or feature has existed since the software release specified by the since-text. For example:

@since 1.5

For source code in the Java platform, this tag indicates the version of the Java platform API specification (not necessarily when it was added to the reference implementation). Multiple @since tags are allowed and are treated like multiple @author tags. You could use multiple tags if the prgram element is used by more than one API.

@throws class-name description

The @throws and @exception tags are synonyms. Adds a "Throws" subheading to the generated documentation, with the class-name and description text. The class-name is the name of the exception that may be thrown by the method. This tag is valid only in the doc comment for a method or constructor. If this class is not fully-specified, the Javadoc tool uses the search order to look up this class. Multiple @throws tags can be used in a given doc comment for the same or different exceptions.

To ensure that all checked exceptions are documented, if a@throws tag does not exist for an exception in the throws clause, the Javadoc tool automatically adds that exception to the HTML output (with no description) as if it were documented with @throws tag.

The @throws documentation is copied from an overridden method to a subclass only when the exception is explicitly declared in the overridden method. The same is true for copying from an interface method to an implementing method. You can use {@inheritDoc} to force @throws to inherit documentation.

For more details, see writing @throws tags.

{@value package.class#field**}**

When {@value} is used (without any argument) in the doc comment of a static field, it displays the value of that constant:

/** * The value of this constant is {@value}. */ public static final String SCRIPT_START = "