javadoc - The Java API Documentation Generator

Generates HTML pages of API documentation from Java source files.

CONTENTS

SYNOPSIS

javadoc [ options ] [ packagenames ] [ sourcefiles ] [ @files ]
Arguments can be in any order.
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. Javadoc uses -sourcepath to look for these package names. Javadoc does not recursively traverse subpackages. Wildcards such as asterisks (*) are not allowed. See Example - Documenting One or More Packages
sourcefiles
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 path that precedes the source file name determines where javadoc will look for it. (Javadoc does not use -sourcepath to look for these source file names.) For example, passing in Button.java is identical to ./Button.java. An example source file name with a full path is /home/src/java/awt/Graphics*.java. See Example - Documenting One or More Classes. You can also mix packagenames and sourcefiles, as in Example - Documenting Both Packages and Classes
@files
One or more files that contain packagenames and sourcefiles in any order, one name per line.

DESCRIPTION

JavadocTM 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, inner classes, interfaces, constructors, methods, and fields.

You can run Javadoc on entire packages, individual source files, or both. In the first case, you pass in as an argument to javadoc a series of package names. In the second case you pass in a series of source (.java) filenames. Examples are given at the end of this document.

NOTE - When you pass in package names to Javadoc, it currently processes all .java classes in the specified package directories, even if the .java files are code examples or other classes that are not actually members of the specified packages. It does not parse each .java file for a package declaration; we may add this parsing in a future release.
Javadoc 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 Javadoc. However, it can link to results from previous runs.

As implemented, Javadoc requires and relies on the java compiler to do its job. Javadoc 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. Javadoc also picks up user-supplied documentation from documentation comments in the source code.

In fact, Javadoc will run on .java source files that are pure stub files with no method bodies. This means you can write documentation comments and run Javadoc 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, Javadoc documents default constructors (section 8.6.7 of Java Language Specification) that are present in the .class files but not in the source code.

When Javadoc builds its internal structure for the documentation, it loads all referenced classes. Because of this, Javadoc 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 Javadoc's class path.

Javadoc Doclets

You can customize the content and format of Javadoc's output by using doclets. Javadoc 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: When a custom doclet is not specified with the -doclet command line option, Javadoc will use the default standard doclet. The javadoc tool has several command line options that are available regardless of which doclet is being used. The standard doclet adds a supplementary set of command line options. Both sets of options are described below in the options section.

Related Documentation

Terminology

A few terms have specific meanings within the context of Javadoc:
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 in the Java Language, namely 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 full documentation is generated during a javadoc run. To be documented, the source files must be available, and either their source filenames or package names must be passed into the javadoc command. We also refer to these as the classes included in the javadoc run, or the included classes.

referenced classes
The classes and interfaces that are explicitly referred to in the definition (implementation) 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, and so forth. Classes referred to in doc comments (such as @see tags) do not qualify as referenced classes. When Javadoc is run, it loads into memory all of the referenced classes in javadoc's bootclasspath and classpath. (Javadoc prints a "Class not found" warning for referenced classes not found.) Javadoc can derive enough information from the 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 external to that javadoc run. Links for names in the documentation to those classes are said to be external references or external links. For example, if you run javadoc 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 not available to the Javadoc run. Therefore, these comments cannot be inherited.


SOURCE FILES

Javadoc 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.

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, see Documentation Comments.

Package Comment Files

Each package can have its own documentation comment, contained in its own "source" file, that Javadoc 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 must name it package.html and place it in the package directory in the source tree along with the .java files. Javadoc will automatically look for this filename in this location. Notice that the filename is identical for all packages. For explicit details, see the example of package.html.

The content of the package comment file is one big documentation comment, 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 tags except {@link} must appear after the description. If you add a @see tag in a package comment file, it must have a fully-qualified name.

When Javadoc runs, it will automatically look for this file; if found, Javadoc 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 Javadoc 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. 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, 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.

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 description. If you add a @see tag, it must have a fully-qualified name.

When you run Javadoc, 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 Javadoc 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 button button.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 Javadoc 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: 
     * <img src="doc-files/Button.gif">
     */

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

Javadoc will generate either two or three HTML frames, as shown in the figure below. When you pass source files (*.java) or a single package name 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: Generated File Structure

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
 * overview-summary.html            Lists all packages with first sentence summaries
   overview-tree.html               Lists class hierarchy for all packages
   deprecated-list.html             Lists deprecated API for all packages
   serialized-form.html             Lists serialized form for all packages
 * overview-frame.html              Lists all packages, used in upper-left frame
   allclasses-frame.html            Lists all classes for all packages, used in lower-left frame
   help-doc.html                    Lists user help for how these pages are organized
   index-all.html                   Default index created without -splitindex option
   index-files                      Directory created with -splitindex option
       index-<number>.html          Index files created with -splitindex option
   package-list                     Lists package names, used only for resolving external refs
   stylesheet.css                   HTML style sheet for defining fonts, colors and positions
   java                             Subpackage directory
       applet                       Subpackage directory
            Applet.html             Page for Applet class
            AppletContext.html      Page for AppletContext interface
            AppletStub.html         Page for AppletStub interface
            AudioClip.html          Page for AudioClip interface
          * package-summary.html    Lists classes with first sentence summaries for this package
          * package-frame.html      Lists classes in this package, used in lower left-hand frame
          * package-tree.html       Lists class hierarchy for this package
            package-use             Lists where this package is used
            doc-files               Directory holding image and example files
            class-use               Directory holding pages API is used
                Applet.html         Page for uses of Applet class
                AppletContext.html  Page for uses of AppletContext interface
                AppletStub.html     Page for uses of AppletStub interface
                AudioClip.html      Page for uses of AudioClip interface

API SIGNATURES

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

public final class Boolean
extends Object
implements Serializable

and the signature for the Boolean.valueOfmethod is:

public static Boolean valueOf(String s)

Javadoc 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 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 in the source code, ahead of declarations for any entity (classes, interfaces, methods, constructors, or fields). These are also known as Javadoc comments. A doc comment consists of the characters between the characters /** that begin the comment and the characters */ that end it. The text can continue onto multiple lines. 

/**
 * This is the typical format of a simple documentation comment.
 */
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 Javadoc will ignore the class comment. 

   /**
    * This is the class comment for the class Whatever.
    */

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

    public class Whatever {
    }
A comment is a description followed by tags - The description begins after the starting delimiter /** and continues until the tag section. The tag section starts with the first character @ that begins a line (ignoring leading asterisks, white space and comment separator). The description cannot continue after the tag section begins. There can be any number of tags -- some types of tags can be repeated while others cannot. This @see starts the tag section: 

/**
 * This is a doc comment.
 * @see java.lang.Object
 */
Standard and in-line tags - A tag is a special keyword within a doc comment that Javadoc can process. Javadoc has standard tags, which appear as @tag, and in-line tags, which appear within braces, as {@tag}. To be interpreted, a standard tag must appear at the beginning of a line, ignoring leading asterisks, white space and comment 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 standard 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. An in-line tag is allowed and interpreted anywhere that text is allowed. The following example contains the standard tag @deprecated and in-line tag {@link}. 

/**
 * @deprecated  As of JDK 1.1, replaced by {@link #setBounds(int,int,int,int)}
 */

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: 

/**
 * This is a <b>doc</b> comment.
 * @see java.lang.Object
 */

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. If you omit the leading asterisk on a line, all leading white space is removed. Therefore, you should not omit leading asterisks if you want leading white space to kept, such as when indenting sample code with the <pre> tag. Without leading asterisks, the indents are lost in the generated documents, since the leading white space is removed.

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 tag. Javadoc 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
Javadoc 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 <H1> and <H2>, because Javadoc 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 Reuse of Method Comments

Javadoc has the ability to automatically reuse or "inherit" method comments. If a method in a class or interface has no doc comment or tags, Javadoc will instead use the comment and tags from a method it either overrides or implements, if any, according to the algorithm below. The overridden method must be a member of a documented class, and not an external referenced class for the doc comment to actually be available to copy. This occurs in three cases:

In the first two cases, for method overrides, Javadoc generates a subheading "Overrides" in the documentation for the overriding method, with a link to the method it is overriding.

In the third case, when a method in a given class implements a method in an interface, Javadoc generates a subheading "Specified by" in the documentation for the overriding method, with a link to the method it is implementing.

Algorithm for Inheriting Method Descriptions - If a method does not have a doc comment, Javadoc 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):
    1. If the superclass has a doc comment for this method, use it.
    2. If step 3a failed to find a doc comment, recursively apply this entire algorithm to the superclass.

JAVADOC TAGS

Javadoc 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.

For information about tags we might introduce in future releases, see Proposed Tags.

The current tags are:

Tag Introduced in JDK/SDK
@author 1.0
{@docRoot} 1.3
@deprecated 1.0
@exception 1.0
{@link} 1.2
@param 1.0
@return 1.0
@see 1.0
@serial 1.2
@serialData 1.2
@serialField 1.2
@since 1.1
@throws 1.2
@version 1.0
@author  name-text
Adds an "Author" entry with the specified name-text to 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, Javadoc 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, use multiple names per line if you want a localized name separator other than comma.

{@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:

  1. On the command line, where the header/footer/bottom are defined: 
       javadoc -bottom '<a href="{@docRoot}/copyright.html">Copyright</a>'
  2. In a doc comment: 
       /**
    * See the <a href="{@docRoot}/copyright.html">Copyright</a>.
    */
The reason this tag is needed is because the generated docs are in hierarchical directories, as deep as the number of subpackages. This expression: 
  <a href="{@docRoot}/copyright.html">
would resolve to: 
  <a href="../../copyright.html">      for java/lang/Object.java
and 
  <a href="../../../copyright.html">   for java/lang/ref/Reference.java

@deprecated  deprecated-text
Adds a comment indicating that this API should no longer be used (even though it may continue to work). Javadoc moves the deprecated-text ahead of the description, placing it in italics and preceding it with a bold warning: "Deprecated".

The first sentence of deprecated-text should at least tell the user when the API was deprecated and what to use as a replacement. Javadoc 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 Javadoc 1.2 and later, use a {@link} tag. This creates the link in-line, where you want it. For example: 
    /**
 * @deprecated  As of JDK 1.1, replaced by {@link #setBounds(int,int,int,int)}
 */
  • For Javadoc 1.1, the standard format is to create a @see tag (which cannot be in-line) for each @deprecated tag.

For more about deprecation, see The @deprecated tag.

@exception  class-name  description
The @exception tag is a synonym for @throws.

{@link  package.class#member  label}
Inserts an in-line link with visible text label that points to the documentation for the specified name in the Java Language that is referenced in a signature of the source files being documented. This tag accepts exactly the same syntax for package.class#member and label as the @see tag, described below, but generates an in-line link rather than placing the link in the "See Also" section. This 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 &#125;

There is no limit to the number of {@link} tags allowed in a sentence. You can use this tag in the description part of a 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 <a href="Component.html#getComponentAt(int, int)">getComponentAt</a> 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. Note that this works only for classes that are referenced in a particular way as described at How a Class Must Be Referenced.

@param  parameter-name description
Adds a parameter to the "Parameters" section. The description may be continued on the next line.

@return  description
Adds a "Returns" section with the description text. This text should describe the return type and permissible range of values.

@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.

@see "string"     Note - This form is broken in version 1.2 (prints none of the quoted text) but fixed in 1.2.2.
Adds a text entry for string. No link is generated. The string is a book or other reference to information not available by URL. Javadoc 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. Javadoc 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 the label when you want the visible text to be abbreviated or different from the name.

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

  • package.class#member is any valid name in the Java Language that is referenced -- a package, class, interface, constructor, method or field name -- except that you replace the dot ahead of the member name with a hash character (#). If this name is in the documented classes, Javadoc will automatically create a link to it. To create links to external referenced classes, use the -link option. Use either of the other two @see forms for referring to documentation of a name that does not belong to a referenced class. This argument is described at greater length below under Specifying a Name.

  • label is optional text that is visible as the link's label. The label can contain whitespace. If label is omitted, then package.class.member will appear, suitably shortened relative to the current class and package -- see How a name is displayed.

  • A space is the delimiter between package.class#member and label. A space inside parentheses does not indicate the start of a label, so spaces may be used between parameters in a method.

Example - In this example, an @see tag (in the Character class) 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: 
<dl>
<dt><b>See Also:</b>
<dd><a href="../../java/lang/String#equals(java.lang.Object)"><code>equals<code></a>
</dl>
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 as java.lang.String#toUpperCase() or not, such as String#toUpperCase() or #toUpperCase(). If less than fully-qualified, Javadoc 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 to providing shorter, "partially-qualified" names is that they are less to type and less clutter in the source code. The following table shows the different forms of the name, where Class can 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,...)

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

Referencing 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
@see  package

The following notes apply to the above table:

  • The first set of forms (with no class or package) will cause Javadoc to search only through the current class's hierarchy. It will find a member of the current class or interface, one of its superclasses or superinterfaces, or one of its enclosing classes or interfaces (search steps 1-3). It will not search the rest of the current package or other packages (search steps 4-5).
  • If any method or constructor is entered as a name with no parentheses, such as getValue, and if there is no field with the same name, Javadoc will correctly create a link to it, but will print a warning message reminding you to add the parentheses and arguments. If this method is overloaded, Javadoc will link to the first method its search encounters, which is unspecified.
  • Inner classes must be specified as outer.inner, not simply inner, for all forms.
  • As stated, the hash character (#), rather than a dot (.) separates a member from its class. This enables Javadoc to resolve ambiguities, since the dot also separates classes, inner classes, packages, and subpackages. However, Javadoc is generally lenient and will properly parse a dot if you know there is no ambiguity, though it will print a warning.

Search order for @see - Javadoc will process a @see tag that appears in a source file (.java), package file (package.html) 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 Javadoc 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 Javadoc 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, modified by the Inner Classes Specification. Javadoc 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

Javadoc 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, Javadoc does not search classes or interfaces within a package in any specified order (that order depends on the particular compiler). In step 5, Javadoc will look in java.lang, since that is automatically imported by all programs.

Javadoc won't 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 java.awt.event.KeyEvent class and refers to a name in the java.awt package, javadoc will not look in that package unless that class imports it.

How a name is displayed - If label is omitted, then package.class.member will appear. In general, it will be suitably shortened relative to the current class and package. By "shortened", we mean Javadoc will display 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 will be displayed only in the latter case:

Type of Reference Example Displays As
@see tag refers to member of the same class @see String#toLowerCase()
toLowerCase()
(omits the class name)
@see tag refers to member of a different class @see Character#toLowerCase(char)
Character.toLowerCase(char)
(includes the class name)

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 <a href="spec.html">Java Spec</a>  //  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. Note that this works only for classes that are referenced in a particular way as described at How a Class Must Be Referenced.

@since  since-text
Adds a "Since" heading with the specified since-text to the generated documentation. The text has no special internal structure. This tag means that this change or feature has existed since the software release specified by the since-text. For example: 
    @since 1.3

@serial  field-description
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.

The @since tag should be added to each serializable field that has been added since the initial version of a Serializable class.

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 the questions "Why does the javadoc standard doclet generate many warnings about missing @serial and/or @serialData tags?" and "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?".

@serialField  field-name  field-type  field-description
Documents an ObjectStreamField component of a Serializable class' 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, and readExternal methods.

@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. If this class is not fully-specified, Javadoc uses the search order to look up this class.

@version  version-text
Adds a "Version" subheading with the specified version-text to the generated docs when the -version option is used. The text has no special internal structure. A doc comment may contain at most one @version tag. Version normally refers to the version of the software (such as the Java 2 SDK) that contains this class or member.


WHERE TAGS CAN BE USED

The following sections describe where the tags can be used. Note that these four tags can be used in all doc comments: @see, @link, @since, @deprecated.


Overview Documentation Tags

Overview tags are tags that can appear in the documentation comment for the overview page (which resides in the source file typically named overview.html). Like in any other documentation comments, these tags must appear after the description.

NOTE - The {@link} tag has a bug in overview documents in version 1.2 -- the text appears properly but has no link.

Overview Tags
@see
{@link}
@since

Package Documentation Tags

Package tags are tags that can appear in the documentation comment for a package (which resides in the source file named package.html).

Package Tags
@see
{@link}
@since
@deprecated

Class and Interface Documentation Tags

The following are tags that can appear in the documentation comment for a class or interface.

Class/Interface Tags
@see
{@link}
@since
@deprecated
@author
@version

An example of a class comment:

/**
 * A class representing a window on the screen.
 * For example:
 * <pre>
 *    Window win = new Window(parent);
 *    win.show();
 * </pre>
 *
 * @author  Sami Shaio
 * @version %I%, %G%
 * @see     java.awt.BaseWindow
 * @see     java.awt.Button
 */
class Window extends BaseWindow {
   ...
}

Field Documentation Tags

The following are the tags that can appear in the documentation comment for a field.

Field Tags
@see
{@link}
@since
@deprecated
@serial
@serialField

An example of a field comment:

    /**
     * The X-coordinate of the component.
     *
     * @see #getLocation()
     */
    int x = 1263732;

Constructor and Method Documentation Tags

The following are the tags that can appear in the documentation comment for a constructor or method.

Method/Constructor Tags
@see
{@link}
@since
@deprecated
@param
@return
@throws (@exception)
@serialData

An example of a method doc comment:

    /**
     * Returns the character at the specified index. An index 
     * ranges from <code>0</code> to <code>length() - 1</code>.
     *
     * @param     index  the index of the desired character.
     * @return    the desired character.
     * @exception StringIndexOutOfRangeException 
     *              if the index is not in the range <code>0</code> 
     *              to <code>length()-1</code>.
     * @see       java.lang.Character#charValue()
     */
    public char charAt(int index) {
       ...
    }

COMMAND LINE ARGUMENT FILE

To shorten or simplify the javadoc command, you may specify one or more files that themselves contain one source filename or package name per line. When executing javadoc, pass in the filename with the '@' leading character to specify it as a file list. When javadoc encounters an argument beginning with the character `@', it operates on the names in that file as if they were on the command line.

For example, you can list all of the package names in a file named packages. This file might look like: 

     com.mypackage1
     com.mypackage2
     com.mypackage3
You could then run javadoc with: 
  % javadoc -d apidocs @packages

OPTIONS
The javadoc tool uses doclets to determine its output. Javadoc uses the default standard doclet unless a custom doclet is specified with the -doclet option. Javadoc provides a set of command-line options that can be used with any doclet -- these options are described below under the sub-heading Javadoc Options. The standard doclet provides an additional set of command-line options that are described below under the sub-heading Options Provided by the Standard Doclet. All option names are case-insensitive, though their arguments can be case-sensitive.

The options are:

-1.1
-author
-bootclasspath
-bottom
-charset
-classpath
-d
-docencoding
-doclet
-docletpath
-doctitle
-encoding
-extdirs
-footer
-group
 -header
-help
-helpfile
-J
-link
-linkoffline
-locale
-nodeprecated
-nodeprecatedlist
-nohelp
-noindex
-nonavbar
-nosince
-notree
-overview
 -package
-private
-protected
-public
-serialwarn
-sourcepath
-splitindex
-stylesheetfile
-title
-use
-verbose
-version
-windowtitle

Javadoc Options

-overview  path/filename
Specifies that javadoc should retrieve the text for the overview documentation from the "source" file specified by path/filename and place it on the Overview page (overview-summary.html). The path/filename is relative to the -sourcepath.

While you can use any name you want for filename and place it anywhere you want for path, a typical thing to do is to name it overview.html and place it in the source tree at the directory that contains the topmost package directories. In this location, no path is needed when documenting packages, since -sourcepath will point to this file. For example, if the source tree for the java.lang package is /src/classes/java/lang/, then you could place the overview file at /src/classes/overview.html. See Real World Example.

For information about the file specified by path/filename, see overview comment file.

Note that the overview page is created only if you pass into javadoc two or more package names. For further explanation, see HTML Frames.)

The title on the overview page is set by -doctitle.

-public
Shows only public classes and members.

-protected
Shows only protected and public classes and members. This is the default.

-package
Shows only package, protected, and public classes and members.

-private
Shows all classes and members.

-help
Displays the online help, which lists these javadoc and doclet command line options.

-doclet  class
Specifies the class file that starts the doclet used in generating the documentation. Use the fully-qualified name. This doclet defines the content and formats the output. If the -doclet option is not used, javadoc uses the standard doclet for generating the default HTML format. This class must contain the start(Root) method. The path to this starting class is defined by the -docletpath option.

For example, to call the MIF doclet, use: 

    -doclet com.sun.tools.doclets.mif.MIFDoclet

-docletpath  classpathlist
Specifies the path to, or jar file containing, the doclet starting class file (specified with the -doclet option) and any jar files it depends on. If classpathlist contains multiple paths or jar files, they should be separated with a colon (:) on Solaris and a semi-colon (;) on Windows. This option is not necessary if the doclet is already in the search path.

-1.1
Generates the documentation with the appearance and functionality of documentation generated by Javadoc 1.1. That is, the pages have a gray background, use images for headers, have bulleted lists instead of tables, have a flat destination directory structure, do not contain inherited API, do not use HTML frames, and do not support inner classes. This option also automatically splits the index into a separate file for each letter of the alphabet. If you want this appearance, this option has the advantage over javadoc 1.1 of having some bugs fixed.

Not all options work with the -1.1 option. To find out which other options are available, execute: 

  % javadoc -1.1 -help
The -footer option shown in this list is functionally the same as the -bottom option described elsewhere on this page. The -title option is functionally the same as -doctitle.

-sourcepath  sourcepathlist
Specifies the search paths for finding source files (.java) when passing package names into the javadoc command. The sourcepathlist can contain multiple paths by separating them with a colon (:). Javadoc will search in all subdirectories of the specified paths.

Note that you can use the -sourcepath option only when passing package names into the javadoc command -- it will not locate .java files passed into the javadoc command. (To locate .java files, cd to that directory or include the path ahead of each file, as shown at Documenting One or More Classes.) If -sourcepath is omitted, javadoc uses the class path to find the source files (see -classpath). Therefore, the default -sourcepath is the value of class path. If -classpath is omitted and you are passing package names into javadoc, it looks in the current directory (and subdirectories) for the source files.

Set sourcepathlist to the root directory of the source tree for the package you are documenting. For example, suppose you want to document a package called com.mypackage whose source files are located at: 

  /home/user/src/com/mypackage/*.java
In this case you would specify the sourcepath to /home/user/src, the directory that contains com/mypackage, and then supply the package name com.mypackage: 
  % javadoc -sourcepath /home/user/src/ com.mypackage
This is easy to remember by noticing that if you concatenate the value of sourcepath and the package name together and change the dot to a slash "/", you end up with the full path to the package: /home/user/src/com/mypackage.

To point to two source paths: 

  % javadoc -sourcepath /home/user1/src:/home/user2/src com.mypackage

-classpath  classpathlist
Specifies the paths where javadoc will look for referenced classes (.class files) -- these are the documented classes plus any classes referenced by those classes. The classpathlist can contain multiple paths by separating them with a colon (:). Javadoc will search in all subdirectories of the specified paths. Follow the instructions in class path documentation for specifying classpathlist.

If -sourcepath is omitted, Javadoc uses -classpath to find the source files as well as class files (for backward compatibility). Therefore, if you want to search for source and class files in separate paths, use both -sourcepath and -classpath.

For example, if you want to document com.mypackage, whose source files reside in the directory /home/user/src/com/mypackage, and if this package relies on a library in /home/user/lib, you would specify: 

  % javadoc -classpath /home/user/lib -sourcepath /home/user/src com.mypackage
As with other tools, if you do not specify -classpath, Javadoc uses the CLASSPATH environment variable, if it is set. If both are not set, Javadoc searches for classes from the current directory.

For an in-depth description of how Javadoc uses -classpath to find user classes as it relates to extension classes and bootstrap classes, see How Classes Are Found.

-bootclasspath  classpathlist
Specifies the paths where the boot classes reside. These are nominally the Java platform classes. The bootclasspath is part of the search path Javadoc will use to look up source and class files. See How Classes Are Found. for more details. Separate directories in classpathlist with colons (:).

-extdirs  dirlist
Specifies the directories where extension classes reside. These are any classes that use the Java Extension mechanism. The extdirs is part of the search path Javadoc will use to look up source and class files. See -classpath (above) for more details. Separate directories in dirlist with colons (:).

-verbose
Provides more detailed messages while javadoc is running. Without the verbose option, messages appear for loading the source files, generating the documentation (one message per source file), and sorting. The verbose option causes the printing of additional messages specifying the number of milliseconds to parse each java source file.

-locale  language_country_variant
Important - The -locale option must be placed ahead (to the left) of any options provided by the standard doclet or any other doclet. Otherwise, the navigation bars will appear in English. This is the only command-line option that is order-dependent.
Specifies the locale that javadoc uses when generating documentation. The argument is the name of the locale, as described in java.util.Locale documentation, such as en_US (English, United States) or en_US_WIN (Windows variant).

Specifying a locale causes javadoc to choose the resource files of that locale for messages (strings in the navigation bar, headings for lists and tables, help file contents, comments in stylesheet.css, and so forth). It also specifies the sorting order for lists sorted alphabetically, and the sentence separator to determine the end of the first sentence. It does not determine the locale of the doc comment text specified in the source files of the documented classes.

-encoding  name
Specifies the encoding name of the source files, such as EUCJIS/SJIS. If this option is not specified, the platform default converter is used.

-Jflag
Passes flag directly to the runtime system java that runs javadoc. Notice there must be no space between the J and the flag. For example, if you need to ensure that the system sets aside 32 megabytes of memory in which to process the generated documentation, then you would call the -Xmx option of java as follows (-Xms is optional, as it only sets the size of initial memory, which is useful if you know the minimum amount of memory required): 
   % javadoc -J-Xmx32m -J-Xms32m com.mypackage
To tell what version of javadoc you are using, call the "-version" option of java: 

   % javadoc -J-version
   java version "1.2"
   Classic VM (build JDK-1.2-V, green threads, sunwjit)

Options Provided by the Standard Doclet

-d  directory
Specifies the destination directory where javadoc saves the generated HTML files. (The "d" means "destination.") Omitting this option causes the files to be saved to the current directory. The value directory can be absolute or relative to the current working directory. For example, the following generates the documentation for the com.mypackage package and saves the results in the /home/user/doc/ directory: 
  % javadoc -d /home/user/doc com.mypackage

-use
Includes one "Use" page for each documented class and package. The page describes what packages, classes, methods, constructors and fields use any API of the given class or package. Given class C, things that use class C would include subclasses of C, fields declared as C, methods that return C, and methods and constructors with parameters of type C.

For example, let's look at what might appear on the "Use" page for String. The getName() method in the java.awt.Font class returns type String. Therefore, getName() uses String, and you will find that method on the "Use" page for String.

Note that this documents only uses of the API, not the implementation. If a method uses String in its implementation but does not take a string as an argument or return a string, that is not considered a "use" of String.

You can access the generated "Use" page by first going to the class or package, then clicking on the "Use" link in the navigation bar.

-version
Includes the @version text in the generated docs. This text is omitted by default. To tell what version of Javadoc you are using, use the -J-version option.

-author
Includes the @author text in the generated docs.

-splitindex
Splits the index file into multiple files, alphabetically, one file per letter, plus a file for any index entries that start with non-alphabetical characters.

-windowtitle  title
Specifies the title to be placed in the HTML <title> tag. This appears in the window title and in any browser bookmarks (favorite places) that someone creates for this page. This title should not contain any HTML tags, as the browser will not properly interpret them. Any internal quotation marks within title may have to be escaped. If -windowtitle is omitted, Javadoc uses the value of -doctitle for this option. 

  % javadoc -windowtitle "Java 2 Platform" com.mypackage
-doctitle  title
Specifies the title to be placed near the top of the overview summary file. The title will be placed as a centered, level-one heading directly beneath the upper navigation bar. The title may contain html tags and white space, though if it does, it must be enclosed in quotes. Any internal quotation marks within title may have to be escaped. 

  % javadoc -doctitle "Java<sup><font size=\"-2\">TM</font></sup>" com.mypackage
-title  title
This option no longer exists. It existed only in Beta versions of Javadoc 1.2. It has been renamed to -doctitle. This option is being renamed to make it clear that it defines the document title rather than the window title.

-header  header
Specifies the header text to be placed at the top of each output file. The header will be placed to the right of the upper navigation bar. header may contain HTML tags and white space, though if it does, it must be enclosed in quotes. Any internal quotation marks within header may have to be escaped. 

  % javadoc -header "<b>Java 2 Platform </b><br>v1.3" com.mypackage

-footer  footer
Specifies the footer text to be placed at the bottom of each output file. The footer will be placed to the right of the lower navigation bar. footer may contain html tags and white space, though if it does, it must be enclosed in quotes. Any internal quotation marks within footer may have to be escaped.

-bottom  text
Specifies the text to be placed at the bottom of each output file. The text will be placed at the bottom of the page, below the lower navigation bar. The text may contain HTML tags and white space, though if it does, it must be enclosed in quotes. Any internal quotation marks within text may have to be escaped.

-link  extdocURL
Creates links to already existing javadoc-generated documentation of external referenced classes. The argument extdocURL is the URL for the external documentation you want to link to. You can supply either an absolute URL or a relative URL -- the latter should be relative to the destination directory (specified with -d). For a link to an external referenced class to actually appear, the class must be referenced as described below in How a Class Must Be Referenced.

In other words, this option enables you to link to classes referenced to by your code but not being documented in the current javadoc run. For these links to go to valid pages, you must know where those HTML pages are located, and specify that location with extdocURL. This allows, for instance, third party documentation to link to java.* documentation on http://java.sun.com. Another use is to for cross-links between sets of packages: Execute javadoc on one set of packages, then run javadoc again on another set of packages, creating links both ways between both sets. A third use is as a "hack" to update docs: Execute javadoc on a full set of packages, then run javadoc again on only the smaller set of changed packages, so that the updated files can be inserted back into the original set. (This is done to save time, but can be tricky -- if you add or remove API from the subset, there will be missing or broken links in the index.)

Use the -link option as follows:

  • Omit the -link option for javadoc to create links only to API within the documentation it is generating in the current run. (Without the -link option, Javadoc does not create links to documentation for external references, because it does not know if (or where) that documentation exists.)

  • Include the -link option for javadoc to also create links to documentation at location extdocURL for external referenced classes.

Note that if the URL is on the World Wide Web, javadoc must have a web connection in order to access the package-list when generating the documentation. If you do not have access, use -linkoffline instead.

How a Class Must be Referenced - For a link to an external referenced class to actually appear, the class must be referenced in a particular way. It is not sufficient for it to be referenced in the body of a method. It must be referenced in either an import statement or in a declaration. Here are examples of how the class java.lang.SecurityManager can be referenced:

  • In an explicit import statement:
    import java.lang.SecurityManager;
    A wildcard import statement does not work (such as import java.lang.*).

  • In the return type or parameter type of a method:
    void foo(SecurityManager sm) {}

  • In an implements, extends or throws statement:
    public abstract class MyClass extends SecurityManager {}

An important corollary is that when you use the -link option, there will probably be many links that do not appear due to this constraint. (The text would appear without a hypertext link.) The only way to find the missing links would be by visual inspection. The most innocuous way to properly reference a class and thereby add the link would be to import that class, as shown above.

Package List - The -link option requires that a file named package-list, which is generated by Javadoc, exist at the URL you specify with -link. The package-list file is a simple text file that lists the names of packages documented at that location. How Javadoc uses the package list is described below.

For example, the package list for the Java 2 Platform v1.3 API is located at http://java.sun.com/products/jdk/1.3/docs/api/package-list. and starts out as follows: 

  java.applet  
  java.awt
  java.awt.color
  java.awt.datatransfer
  java.awt.dnd
  java.awt.event
  java.awt.font
  etc.

When javadoc is run without the -link option, as it is generating documentation, when it encounters a name that belongs to an external referenced class, it prints the name with no link. However, when the -link option is used, Javadoc searches the package-list file at the specified extdocURL location for that package name. If it finds the package name, it prefixes the name with that URL.

In order for there to be no broken links, all of the documentation for the external references must exist at the specified URLs. Javadoc will not check that these pages exist -- only that the package-list exists.

The package-list file is created but is empty if the argument to javadoc is source files rather than packages.

Example - For example, the following command causes Javadoc to look for a package-list file at the given URL, reads in the package names in that file, and then uses the given URL when adding links to API in those external packages: 

  % javadoc -link http://java.sun.com/products/jdk/1.3/docs/api com.mypackage
Multiple Links - You can supply multiple -link options to link to any number of external generated documents.   Known Bug - Javadoc 1.2 has a known bug which prevents you from supplying more than one -link command. This is fixed in 1.2.2.

Specify a different link option for each external document to link to:

   % javadoc -link extdocURL1 -link extdocURL2 ... -link extdocURLn com.mypackage

where extdocURL1,  extdocURL2,  ... extdocURLn point respectively to the roots of external documents, each of which contains a file named package-list.

Cross-links - Note that "bootstrapping" may be required when cross-linking two or more documents that have not previously been generated. In other words, if package-list does not exist for either document, when you run javadoc on the first document, the package-list will not yet exist for the second document. Therefore, to create the external links, you must re-generate the first document after generating the second document.

In this case, the purpose of first generating a document is to create its package-list (or you can create it by hand it if you're certain of the package names). Then generate the second document with its external links. Javadoc prints a warning if a needed external package-list file does not exist.

Updating docs - The third use for -link option is useful if your project has dozens or hundreds of packages, if you have already run javadoc on the entire tree, and now, in a separate run, you want to quickly make some small changes and re-run javadoc on just a small portion of the source tree. This is somewhat of a hack in that it works properly only if your changes are only to doc comments and not to signatures. If you were to add, remove or change any signatures from the source code, then broken links could show up in the index, package tree, inherited member lists, use page, or other places.

First, you create a new destination directory for this new small run and set -link and -d to that same relative path: If the original docs are in a directory named html: 

  % javadoc -d update -link . html com.mypackage
When javadoc is done, copy these generated files in update over the original files in html.

Background information: In general, when javadoc runs, it has the potential to generate links for names that appear throughout its generated pages: in signatures, @see tags, {@link} tags, summaries, hierarchies, the overview, and the index. Some of these links will go to pages generated in the current run, while other links will potentially go to pages not generated in the current run.

-linkoffline  extdocURL  packagelistLoc
This option is a variation of -link; they both create links to documentation for external referenced classes, where the classes must be referenced as described above in How a Class Must Be Referenced.

You must use this option instead of -link if, at the time you run javadoc, the external document's package-list file does not exist at the extdocURL location (is "offline") but exists at a different location packageListLoc (typically local). This can happen when the shell you are running javadoc in does not have web access to the extdocURL. Thus, if extdocURL is accessible only on the World Wide Web, -linkoffline removes the constraint that javadoc have a web connection when generating the documentation. Examples are given below.

You can specify multiple -linkoffline options in a given javadoc run. (Prior to 1.2.2, it could be specified only once.)

The arguments are:

  • extdocURL is the URL for the root location of the external javadoc-generated documentation you want to link to. This location can be an absolute or relative URL -- if relative, make it relative to the destination directory (specified with -d).

  • packagelistLoc is the location to the directory containing the package-list file for the external documentation. This can be a URL (http: or file:) or file path, and can be absolute or relative. If relative, make it relative to the current directory from where javadoc was run. Do not include the package-list filename.

For example, if you want to link to the java.lang package at http://java.sun.com/products/jdk/1.3/docs/api, but your shell does not have web access, then you could access the package-list file using http://java.sun.com/products/jdk/1.3/docs/api/package-list, save it to a local directory, and point to this local copy with packagelistLoc.

If a package-list file does not yet exist, but you know what package names your document will link to, you can create your own copy of this file by hand and specify its path with packagelistLoc. This is useful when you need to generate documentation that links to new external documentation whose package names you know, but which is not yet published. This is also a way of creating a package-list file for linking to documentation generated with Javadoc 1.0 or 1.1, earlier versions where package-list files were not generated.

Two companies can share their unpublished package-list files, enabling them to release their cross-linked documentation simultaneously.

As shown below, to use this option, specify extdocURL1, the location of the javadoc-generated documentation for external referenced classes, and packagelistLoc1, the location of its package-list file. Include -linkoffline once for each generated document you want to refer to (each option is shown on a separate line for clarity):

% javadoc -linkoffline extdocURL1 packagelistLoc1 \
          -linkoffline extdocURL2 packagelistLoc2 \
          ...

For example, the following command adds links pointing to a document (whose root is specified by the first argument), for packages listed in the /jdk/package-list file (as specified by the second argument). It generates documentation for the com.mypackage package. 

% javadoc -linkoffline http://java.sun.com/products/jdk/1.3/docs/api /jdk com.mypackage

-group  groupheading  packagepattern:packagepattern:...
Separates packages on the overview page into whatever groups you specify, one group per table. You specify each group with a different -group option. The groups appear on the page in the order specified on the command line; packages are alphabetized within a group. For a given -group option, the packages matching the list of packagepattern expressions appear in a table with the heading groupheading.

  • groupheading can be any text, and can include white space. This text is placed in the table heading for the group.

  • packagepattern can be any package name, or can be the start of any package name followed by an asterisk (*). The asterisk is a wildcard meaning "match any characters". This is the only wildcard allowed. Multiple patterns can be included in a group by separating them with colons (:).
NOTE: If using an asterisk in a pattern or pattern list, the pattern list must be inside quotes, such as "java.lang*:java.util"

If you do not supply any -group option, all packages are placed in one group with the heading "Packages". If the all groups do not include all documented packages, any leftover packages appear in a separate group with the heading "Other Packages".

For example, the following option separates the four documented packages into core, extension and other packages. Notice the trailing "dot" does not appear in "java.lang*" -- including the dot, such as "java.lang.*" would omit the java.lang package. 

  % javadoc -group "Core Packages" "java.lang*:java.util"
            -group "Extension Packages" "javax.*"
            java.lang java.lang.reflect java.util javax.servlet java.new
This results in the groupings:
Core Packages
java.lang
java.lang.reflect
java.util
Extension Packages
javax.servlet
Other Packages
java.new

-nodeprecated
Prevents the generation of any deprecated API at all in the documentation. This does what -nodeprecatedlist does, plus it does not generate any deprecated API throughout the rest of the documentation. This is useful when writing code and you don't want to be distracted by the deprecated code.

-nodeprecatedlist
Prevents the generation of the file containing the list of deprecated APIs (deprecated-list.html) and the link in the navigation bar to that page. (However, javadoc continues to generate the deprecated API throughout the rest of the document.) This is useful if your source code contains no deprecated API, and you want to make the navigation bar cleaner.

-nosince
Omits from the generated docs the "Since" sections associated with the @since tags.

-notree
Omits the class/interface hierarchy from the generated docs. The hierarchy is produced by default.

-noindex
Omits the index from the generated docs. The index is produced by default.

-nohelp
Omits the HELP link in the navigation bars at the top and bottom of each page of output.

-nonavbar
Prevents the generation of the navigation bar, header and footer, otherwise found at the top and bottom of the generated pages. Has no affect on the "bottom" option. The -nonavbar option is useful when you are interested only in the content and have no need for navigation, such as converting the files to PostScript or PDF for print only.

-helpfile  path/filename
Specifies the path of an alternate help file path/filename that the HELP link in the top and bottom navigation bars link to. Without this option, Javadoc automatically creates a help file help-doc.html that is hard-coded in Javadoc. This option enables you to override this default. The filename can be any name and is not restricted to help-doc.html -- Javadoc will adjust the links in the navigation bar accordingly. For example: 
  % javadoc -helpfile /home/user/myhelp.html java.awt
-stylesheetfile  path/filename
Specifies the path of an alternate HTML stylesheet file. Without this option, Javadoc automatically creates a stylesheet file stylesheet.css that is hard-coded in Javadoc. This option enables you to override this default. The filename can be any name and is not restricted to stylesheet.css. For example: 
  % javadoc -stylesheetfile /home/user/mystylesheet.css com.mypackage
-serialwarn
Generates compile-time warnings for missing @serial tags. By default, Javadoc 1.2.2 (and later versions) generates no serial warnings. (This is a reversal from earlier versions.) Use this option to display the serial warnings, which helps to properly document default serializable fields and writeExternal methods.

-charset  name
Specifies the HTML character set for this document. For example: 
  % javadoc -charset "iso-8859-1" mypackage
would insert the following line in the head of every generated page: 
   <META http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
This META tag is described in the HTML standard. (4197265 and 4137321)

-docencoding  name
Specifies the encoding of the generated HTML files.


SIMPLE EXAMPLES

You can run javadoc on entire packages or individual classes. Each package name has a corresponding directory name. In the following examples, the source files are located at /home/src/java/awt/*java. The destination directory is /home/html.

Documenting One or More Packages

To document a package, the source files (*.java) for that package must be located in a directory having the same name as the package. If a package name is made up of several identifiers (separated by dots), each identifier represents a different directory. Thus, all java.awt classes must reside in a directory named java/awt/. You can run javadoc either of the following two ways -- by changing directories (with cd) or by using -sourcepath option. You cannot use wildcards to specify groups of packages.

Both cases generate HTML-formatted documentation for the public and protected classes and interfaces in packages java.awt and java.awt.event and save the HTML files in the specified destination directory (/home/html). Because two or more packages are being generated, the document has three frames -- for the list of packages, the list of classes, and the main page.

Documenting One or More Classes

The second way to run Javadoc is by passing in one or more source files (.java). You can run javadoc either of the following two ways -- by changing directories (with cd) or by fully-specifying the path to the .java files. Relative paths are relative to the current directory. The -sourcepath option is ignored when passing in source files. You can use command line wildcards, such as asterisk (*), to specify groups of classes.

Documenting Both Packages and Classes

You can document entire packages and individual classes at the same time. Here's an example that mixes two of the previous examples. You can use -sourcepath for the path to the packages but not for the path to the individual classes. 
  % javadoc -d /home/html -sourcepath /home/src java.awt /home/src/java/applet/Applet.java
This example generates HTML-formatted documentation for the package java.awt and class Applet. (Javadoc determines the package name for Applet from the package declaration, if any, in the Applet.java source file.)

REAL WORLD EXAMPLE

Javadoc has many useful options, some of which are more commonly used than others. Here is effectively the command we use to run Javadoc on the Java platform API. We use 180MB of memory to generate the documentation for the 1500 (approx.) public and protected classes in the Java 2 Platform, Standard Edition, v1.2.

The same example is shown twice -- first as executed on the command line, then as executed from a makefile. It uses absolute paths in the option arguments, which enables the same Javadoc command to be run from any directory.

Command Line Example

This command line example is over 900 characters, which is too long for some shells, such as DOS. You can write a shell script instead to execute this command. 
% javadoc -sourcepath /java/jdk/src/share/classes            \
    -overview /java/jdk/src/share/classes/overview.html      \
    -d /java/jdk/build/api                                   \
    -use                                                     \
    -splitIndex                                              \
    -windowtitle 'Java 2 Platform v1.2 API Specification'    \
    -doctitle 'Java<sup><font size="-2">TM</font></sup> 2 Platform v1.2 API Specification' \
    -header '<b>Java 2 Platform </b><br><font size="-1">v1.2</font>' \
    -bottom '<font size="-1"><a href="http://java.sun.com/cgi-bin/bugreport.cgi">Submit 
a bug or feature</a><br><br>Java is a trademark or registered trademark of Sun Microsystems, 
Inc. in the US and other countries.<br>Copyright 1993-1999 Sun Microsystems, Inc. 
901 San Antonio Road,<br>Palo Alto, California, 94303, U.S.A. All Rights Reserved.</font>' \  
    -group "Core Packages" "java.*:com.sun.java.*:org.omg.*" \
    -group "Extension Packages" "javax.*"                    \
    -J-Xmx180m                                               \  
    @filelist
where filelist is the name of a file containing the packages to process, such as java.applet java.lang. None of the options should contain any newline characters between the single quotes. (For example, if you copy and paste this example, delete the newline characters from the -bottom option.) See the other notes listed below.

Makefile Example

This is an example of a GNU makefile. For an example of a Windows makefile, see creating a makefile for Windows. 
javadoc -sourcepath $(SRCDIR)              \   /* Sets path for source files     */
        -overview $(SRCDIR)/overview.html  \   /* Sets file for overview text    */
        -d /java/jdk/build/api             \   /* Sets destination directory     */
        -use                               \   /* Adds "Use" files               */
        -splitIndex                        \   /* Splits index A-Z               */
        -windowtitle $(WINDOWTITLE)        \   /* Adds a window title            */
        -doctitle $(DOCTITLE)              \   /* Adds a doc title               */
        -header $(HEADER)                  \   /* Adds running header text       */
        -bottom $(BOTTOM)                  \   /* Adds text at bottom            */
        -group $(GROUPCORE)                \   /* 1st subhead on overview page   */
        -group $(GROUPEXT)                 \   /* 2nd subhead on overview page   */
        -J-Xmx180m                         \   /* Sets memory to 180MB           */
        java.lang java.lang.reflect        \   /* Sets packages to document      */
        java.util java.io java.net         \
        java.applet
        
WINDOWTITLE = 'Java 2 Platform v1.2 API Specification'
DOCTITLE = 'Java<sup><font size="-2">TM</font></sup> 2 Platform v1.2 API Specification'
HEADER = '<b>Java 2 Platform </b><br><font size="-1">v1.2</font>'
BOTTOM = '<font size="-1"><a href="http://java.sun.com/cgi-bin/bugreport.cgi">Submit
    a bug or feature</a><br><br>Java is a trademark or registered trademark 
    of Sun Microsystems, Inc. in the US and other countries.<br>Copyright 1993-1999    
    Sun Microsystems, Inc. 901 San Antonio Road,<br>Palo Alto, California, 94303, U.S.A.  
    All Rights Reserved.</font>'
GROUPCORE = '"Core Packages" "java.*:com.sun.java.*:org.omg.*"'
GROUPEXT  = '"Extension Packages" "javax.*"'
SRCDIR = '/java/jdk/1.2/src/share/classes'

Single quotes are used to surround makefile arguments.

NOTES


ENVIRONMENT

CLASSPATH
Environment variable that provides the path which javadoc uses to find user class files. This environment variable is overridden by the -classpath option. Separate directories with a colon, for example: 
.:/home/classes:/usr/local/java/classes

TROUBLESHOOTING

There is currently no documentation for Javadoc error messages. Troubleshooting tips can be found on the Javadoc FAQ

SEE ALSO

Please send comments to: javadoc-tool@sun.com

JavadocTM is a trademark of Sun Microsystems, Inc. (The javadoc command itself does not require the trademark symbol.)