javadoc(1) javadoc(1) Name javadoc - The Java API Documentation Generator Generates HTML pages of API documentation from Java source files. This document contains Javadoc examples for Solaris. SYNOPSIS javadoc [ options ] [ packagenames ] [ sourcefilenames ] [ -subpack‐ ages pkg1:pkg2:... ] [ @argfiles ] Arguments can be in any order. See processing of Source Files for details on how the Javadoc tool determines which ".java" files to process. options Command-line options, as specified in this document. To see a typi‐ cal 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 the Java Language Specification). There‐ fore, 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, package‐ names and sourcefilenames in any order. Wildcards (*) and -J options are not allowed in these files. DESCRIPTION The Javadoc 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 -subpack‐ ages 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 cov‐ ered 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: o Its name, after stripping off the ".java" suffix, is actually a legal class name (see the Java Language Specification for legal characters) o Its directory path relative to the root of the source tree is actu‐ ally a legal package name (after converting its separators to dots) o Its package statement contains the legal package name (specified in the previous bullet) 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: o Declarations (return types, argument types, field types) o "See Also" sections generated from @see tags o In-line text generated from {@link} tags o Exception names generated from @throws tags o "Specified by" links to members in interfaces and "Overrides" links to members in classes o Summary tables listing packages, classes and members o Package and class inheritance trees o The index You can add hyperlinks to existing text for classes not included on the command line (but generated separately) by way of the -link and -linkof‐ fline options. Other processing details - The Javadoc tool produces one complete docu‐ ment 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 decla‐ rations, 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 from documentation 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 (see 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 trou‐ bleshooting is done. For example, according to the Java Language Specifi‐ cation, 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 documenta‐ tion, 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 @ http://docs.oracle.com/javase/7/docs/technotes/tools/findingclasses.html. Generally speaking, classes you create must either be loaded as an exten‐ sion 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. Infor‐ mation about doclets and their use is at the following locations: o Javadoc Doclets @ http://docs.oracle.com/javase/7/docs/tech‐ notes/guides/javadoc/index.html o The -doclet command-line option When a custom doclet is not specified with the -doclet command line option, the Javadoc tool will use the default standard doclet. The javadoc tool has several command line options that are available regard‐ less of which doclet is being used. The standard doclet adds a supplemen‐ tary set of command line options. Both sets of options are described below in the options section. Related Documentation and Doclets o Javadoc Enhancements @ http://docs.oracle.com/javase/7/docs/tech‐ notes/guides/javadoc/index.html for details about improvements added in Javadoc. o Javadoc FAQ @ http://java.sun.com/j2se/javadoc/faq/index.html for answers to com‐ mon questions, information about Javadoc-related tools, and work‐ arounds for bugs. o How to Write Doc Comments for Javadoc @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html for more information about Sun conventions for writing documentation comments. o Requirements for Writing API Specifications @ http://java.sun.com/j2se/javadoc/writingapispecs/index.html - Stan‐ dard requirements used when writing the Java SE Platform Specifica‐ tion. It can be useful whether you are writing API specifications in source file documentation comments or in other formats. It covers requirements for packages, classes, interfaces, fields and methods to satisfy testable assertions. o Documentation Comment Specification @ http://java.sun.com/docs/books/jls/first_edition/html/18.doc.html - The original specification on documentation comments, Chapter 18, Documentation Comments, in the Java Language Specification, First Edition, by James Gosling, Bill Joy, and Guy Steele. (This chapter was removed from the second edition.) o DocCheck Doclet @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-141437.html - Checks doc comments in source files and generates a report listing the errors and irregularities it finds. It is part of the Doc Check Utilities. o MIF Doclet @ http://java.sun.com/j2se/javadoc/mifdoclet/ - Can automate the gen‐ eration of API documentation in MIF, FrameMaker and PDF formats. MIF is Adobe FrameMaker's interchange format. Terminology The terms documentation comment, doc comment, main description, tag, block tag, and in-line tag are described at Documentation 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 gen‐ erated 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 @ http://docs.ora‐ cle.com/javase/1.3/docs/tooldocs/solaris/javadoc.html#referenced‐ classes.) When the Javadoc tool is run, it should load into memory all of the referenced classes in javadoc's bootclasspath and class‐ path. (The Javadoc tool prints a "Class not found" warning for ref‐ erenced 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 com‐ ments 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 unpro‐ cessed 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 doc‐ ument. 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 the Javadoc tool will merge into the package summary page that it generates. You typically include in this comment any docu‐ mentation that applies to the entire package. To create a package comment file, you have a choice of two files to place your comments: o package-info.java - Can contain a package declaration, package anno‐ tations, package comments and Javadoc tags. This file is generally preferred over package.html. o package.html - Can contain only package comments and Javadoc tags, no package annotations. A package may have a single package.html file or a single pack‐ age-info.java file but not both. Place either file in the package direc‐ tory in the source tree along with your .java files. package-info.java - This file can contain a package comment of the fol‐ lowing structure -- the comment is placed before the package declaration: File: java/applet/package-info.java /** * Provides the classes necessary to create an * applet and the classes an applet uses * to communicate with its applet context. * <p> * 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 */ package java.lang.applet; Note that while the comment separators /** and /* must be present, the leading asterisks on 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 <HTML> <BODY> Provides the classes necessary to create an applet and the classes an applet uses to communicate with its applet context. <p> 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 </BODY> </HTML> 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 aster‐ isks. When writing the comment, you should make the first sentence a sum‐ mary 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 descrip‐ tion. 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 @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html#packagecomments. 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: o Copies the comment for processing. (For package.html, copies all content between <body> and </body> HTML tags. You can include a <head> section to put a <title>, source file copyright statement, or other information, but none of these will appear in the generated documentation.) o Processes any package tags that are present. o Inserts the processed text at the bottom of the package summary page it generates, as shown in Package Summary @ http://docs.oracle.com/javase/7/docs/api/java/applet/package-sum‐ mary.html. o Copies the first sentence of the package comment to the top of the package summary page. It also adds the package name and this first sentence to the list of packages on the overview page, as shown in Overview Summary @ http://docs.oracle.com/javase/7/docs/api/overview-summary.html. The end-of-sentence is determined by the same rules used for the end of the first sentence of class and member main descriptions. 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 direc‐ tory, you could create an overview comment file at /home/user/src/over‐ view.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 docu‐ mentation. 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 com‐ ment, written in HTML, like the package comment file described previ‐ ously. See that description for details. To re-iterate, when writing the comment, you should make the first sentence a summary about the applica‐ tion 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. o Copies all content between <body> and </body> tags for processing. o Processes any overview tags that are present. o Inserts the processed text at the bottom of the overview page it generates, as shown in Overview Summary @ http://docs.oracle.com/javase/7/docs/api/overview-summary.html. o Copies the first sentence of the overview comment to the top of the overview summary page. 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 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 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: * <img src="doc-files/Button.gif"> */ Test Files and Template Files Some developers have indicated they want to store test files and tem‐ plates files in the source tree near their corresponding source files. That is, they would like to put them in the same directory, or a subdi‐ rectory, 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, com‐ pilable 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 speci‐ fying 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 subdirec‐ tory. 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/pack‐ age1/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 information about Identifiers in the Java Language Specification). 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 gen‐ erates files with two types of names: those named after classes/inter‐ faces, 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 o One class or interface page (classname.html) for each class or interface it is documenting. o One package page (package-summary.html) for each package it is docu‐ menting. The Javadoc tool will include any HTML text provided in a file named package.html or package-info.java in the package direc‐ tory of the source tree. o One overview page (overview-summary.html) for the entire set of packages. This is the front page of the generated document. The Javadoc tool will include any HTML text provided in a file specified with the -overview option. Note that this file is created only if you pass into javadoc two or more package names. For further expla‐ nation, see HTML Frames.) Cross-Reference Pages o One class hierarchy page for the entire set of packages (over‐ view-tree.html). To view this, click on "Overview" in the navigation bar, then click on "Tree". o One class hierarchy page for each package (package-tree.html) To view this, go to a particular package, class or interface page; click "Tree" to display the hierarchy for that package. o One "use" page for each package (package-use.html) and a separate one for each class and interface (class-use/classname.html). This page describes what packages, classes, methods, constructors and fields use any part of the given class, interface or package. Given a class or interface A, its "use" page includes subclasses of A, fields declared as A, methods that return A, and methods and con‐ structors with parameters of type A. You can access this page by first going to the package, class or interface, then clicking on the "Use" link in the navigation bar. o A deprecated API page (deprecated-list.html) listing all deprecated names. (A deprecated name is not recommended for use, generally due to improvements, and a replacement name is usually given. Deprecated APIs may be removed in future implementations.) o A constant field values page (constant-values.html) for the values of static fields. o A serialized form page (serialized-form.html) for information about serializable and externalizable classes. Each such class has a description of its serialization fields and methods. This informa‐ tion is of interest to re-implementors, not to developers using the API. While there is no link in the navigation bar, you can get to this information by going to any serialized class and clicking "Serialized Form" in the "See also" section of the class comment. The standard doclet automatically generates a serialized form page: any class (public or non-public) that implements Serializable is included, along with readObject and writeObject methods, the fields that are serialized, and the doc comments from the @serial, @serial‐ Field, and @serialData tags. Public serializable classes can be excluded by marking them (or their package) with @serial exclude, and package-private serializable classes can be included by marking them (or their package) with @serial include. As of 1.4, you can generate the complete serialized form for public and private classes by running javadoc without specifying the -private option. o An index (index-*.html) of all class, interface, constructor, field and method names, alphabetically arranged. This is internationalized for Unicode and can be generated as a single file or as a separate file for each starting character (such as A-Z for English). Support Files o A help page (help-doc.html) that describes the navigation bar and the above pages. You can provide your own custom help file to over‐ ride the default using -helpfile. o One index.html file which creates the HTML frames for display. This is the file you load to display the front page with frames. This file itself contains no text content. o Several frame files (*-frame.html) containing lists of packages, classes and interfaces, used when HTML frames are being displayed. o A package list file (package-list), used by the -link and -linkof‐ fline options. This is a text file, not HTML, and is not reachable through any links. o A style sheet file (stylesheet.css) that controls a limited amount of color, font family, font size, font style and positioning on the generated pages. o A doc-files directory that holds any image, example, source code or other files that you want copied to the destination directory. These files are not processed by the Javadoc tool in any manner -- that is, any javadoc tags in them will be ignored. This directory is not generated unless it exists in the source tree. 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 pack‐ ages). That is, when you pass a single package name or source files (*.java) belonging to a single package as arguments into the javadoc com‐ mand, 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. Load one of the following two files as the starting page depending on whether you want HTML frames or not: o index.html (for frames) o overview-summary.html (for no frames) Generated File Structure The generated class and interface files are organized in the same direc‐ tory 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 constant-values.html Lists values of static fields 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 Package 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 src-html Source code directory java Package directory applet Subpackage directory Applet.html Page for Applet source code AppletContext.html Page for AppletContext source code AppletStub.html Page for AppletStub source code AudioClip.html Page for AudioClip source code 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 the Boolean 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 meth‐ ods. 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, construc‐ tor, or field. You can also create doc comments for each package 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 charac‐ ters 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. /** * This is the typical format of a simple documentation comment * that spans two 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. /** * This is the class comment for the class Whatever. */ 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 con‐ tinues until the tag section. The tag section starts with the first block tag, which is defined by the first @ character that begins a line (ignor‐ ing leading asterisks, white space, and leading separator /**). It is possible to have a comment with only a tag section and no main descrip‐ tion. 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 exam‐ ple, this @see starts the tag section: /** * This sentence would hold the main description for this doc comment. * @see java.lang.Object */ Block tags and in-line tags - A tag is 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 inter‐ preted, 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 @. 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 con‐ tains the block 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 which‐ ever version of HTML your browser supports; we have written the standard doclet to generate HTML 3.2-compliant code elsewhere (outside of the doc‐ umentation 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 < and >. Likewise, the ampersand (&) should be written &. 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. 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. Spa‐ ces 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 sum‐ mary 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 mem‐ bers, it's best not to use HTML heading tags such as <H1> and <H2>, because the Javadoc tool creates an entire structured document and these structural tags might interfere with the formatting of the generated doc‐ ument. 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. Construc‐ tors, fields and nested classes do not inherit doc comments. o Automatically inherit comment to fill in missing text - When a main description, or @return, @param or @throws tag is missing from a method comment, the Javadoc tool copies the corresponding main description or tag comment from the method it overrides or imple‐ ments (if any), according to the algorithm below. More specifically, when a @param tag for a particular parameter is missing, then the comment for that parameter is copied from the method further up the inheritance hierarchy. When a @throws tag for a partic‐ ular exception is missing, the @throws tag is copied only if that exception is declared. This behavior contrasts with version 1.3 and earlier, where the pres‐ ence of any main description or tag would prevent all comments from being inherited. o Explicitly inherit comment with {@inheritDoc} tag - Insert the inline tag {@inheritDoc} in a method main description or @return, @param or @throws tag comment -- the corresponding inherited main description or tag comment is copied into that spot. The source file for the inherited method need only be on the path speci‐ fied by -sourcepath for 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: o When a method in a class overrides a method in a superclass o When a method in an interface overrides a method in a superinterface o When a method in a class implements a method in an interface 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) inter‐ face, 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): a. If the superclass has a doc comment for this method, use it. b. 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: o Block tags - Can be placed only in the tag section that follows the main description. Block tags are of the form: @tag. o Inline tags - Can be placed anywhere in the main description or in the comments for block tags. Inline tags are denoted by curly braces: {@tag}. For information about tags we might introduce in future releases, see Proposed Tags @ http://java.sun.com/j2se/javadoc/proposed-tags.html. 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-text to the gener‐ ated docs when the -author option is used. A doc comment may con‐ tain 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 and writing @author tags @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html#@author. @deprecated deprecated-text Note: 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 depre‐ cated-text ahead of the main description, placing it in italics and pre‐ ceding 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. Subse‐ quent 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, see writing @deprecated tags @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html#@deprecated. o 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)} */ o 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 @ http://docs.oracle.com/javase/7/docs/technotes/guides/javadoc/depreca‐ tion/index.html. {@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 (< and >) in doc com‐ ments, 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 {@lit‐ eral}. {@docRoot} Represents the relative path to the generated document's (destina‐ tion) 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 '<a<EMAIL_ADDRESS>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 <a<EMAIL_ADDRESS>*/ 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<EMAIL_ADDRESS>would resolve to: <a href="../../copyright.html"> for java/lang/Object.java and <a href="../../../copyright.html"> 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: o In the main description block of a method. In this case, the main description is copied from a class or interface up the hierarchy. o In the text arguments of the @return, @param and @throws tags of a method. In this case, the tag text is copied from the corre‐ sponding tag up the hierarchy. See Automatic Copying of Method Comments for a more precise descrip‐ tion of how comments are found in the inheritance hierarchy. Note that if this tag is missing, the comment is or is not automatically inher‐ ited 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 @depre‐ cated). This tag is very simliar to @see -- both require the same references and accept exactly the same syntax for package.class#member and 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 description part 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 <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. For more details, see writing {@link} tags @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html#{@link}. {@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 (< and >) 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: A<B>C 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 con‐ structor, or the name of a type parameter of a class, method or con‐ structor. 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 @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html#@param. @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 @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html#@return. @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, con‐ structor, 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 charac‐ ter. 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 docu‐ mentation 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 pack‐ age 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 automat‐ ically 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. o package.class#member is any valid program element name that is referenced -- a package, class, interface, constructor, method or field name -- except that the character ahead of the member name should be a hash character (#). The class represents any top-level or nested class or interface. The member represents any constructor, method or field (not a nested class or inter‐ face). If this name is in the documented classes, the Javadoc tool 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 documenta‐ tion of a name that does not belong to a referenced class. This argument is described at greater length below under Spec‐ ifying a Name. o 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 dis‐ played. o 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, 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 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 pack‐ age.class#member Referencing a member of the cur‐ rent class @see #field @see #method(Type, Type,...) @see #method(Type argname, Type argname,...) @see #constructor(Type, Type,...) @see #construc‐ tor(Type argname, Type argname,...) Referencing another class in the cur‐ rent 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#construc‐ tor(Type argname, Type argname,...) @see Class.NestedClass @see Class Referencing an element in another pack‐ age (fully qualified) @see package.Class#field @see pack‐ age.Class#method(Type, Type,...) @see pack‐ age.Class#method(Type argname, Type argname,...) @see package.Class#construc‐ tor(Type, Type,...) @see package.Class#construc‐ tor(Type argname, Type argname,...) @see package.Class.NestedClass @see package.Class @see package The following notes apply to the above table: o The first set of forms (with no class or package) will cause the Javadoc tool 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 pack‐ ages (search steps 4-5). o 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, the Javadoc tool 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, the Javadoc tool will link to the first method its search encounters, which is unspecified. o Nested classes must be specified as outer.inner, not simply inner, for all forms. o As stated, the hash character (#), rather than a dot (.) sepa‐ rates a member from its class. This enables the Javadoc tool to resolve ambiguities, since the dot also separates classes, nested classes, packages, and subpackages. However, the Javadoc tool 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 - 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 lat‐ ter two files, you must fully-qualify the name you supply with @see. In a source file, you can specify a name that is fully-quali‐ fied 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 the Java Language Specification. 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 gen‐ erated 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 pack‐ age.class.member appears. In general, it is suitably shortened rel‐ ative 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 follow‐ ing table. Use -noqualifier to globally remove the package names. Type of Reference Example in String.toUp‐ Displays As perCase() @see tag refers to @see String#toLowerCase() toLowerCase() (omits member of the same the package and class, same package class names) @see tag refers to @see Character#toLower‐ Character.toLower‐ member of a differ‐ Case(char) Case(char) (omits ent class, same the package name, package includes the class name) @see tag refers to @see java.io.File.exists() member of a differ‐ java.io.File#exists() (includes the pack‐ ent class, different age and class names) package 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. For more details, see writing @see tags @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html#@see. @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 seri‐ alized 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: o A public or protected class that implements Serializable is included unless that class (or its package) is marked @serial exclude. o A private or package-private class that implements Serializable is excluded unless that class (or its package) is marked @serial include. Examples: The javax.swing package is marked @serial exclude (in pack‐ age.html or package-info.java). The public class java.secu‐ rity.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 exam‐ ple, see " Documenting Serializable Fields and Data for a Class @ http://docs.oracle.com/javase/7/docs/platform/serializa‐ tion/spec/serial-arch.html," Section 1.6 of the Java Object Serializa‐ tion Specification. Also see the Serialization FAQ @ http://java.sun.com/javase/technologies/core/basic/serialization‐ FAQ.jsp#javadoc_warn_missing, 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 @ http://java.sun.com/j2se/javadoc/writingapispecs/serialized-crite‐ ria.html 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 writeOb‐ ject, readObject, writeExternal, readExternal, writeReplace, and read‐ Resolve methods. @since since-text Adds a "Since" heading with the specified since-text to the gener‐ ated 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 mul‐ tiple 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" sub‐ heading 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 com‐ ment for a method or constructor. If this class is not fully-speci‐ fied, 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 descrip‐ tion) 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 over‐ ridden 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 @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html#@exception. {@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 = "<script>" When used with argument package.class#field in any doc comment, it displays the value of the specified constant: /** * Evaluates the script starting with {@value #SCRIPT_START}. */ public String evalScript(String script) { } The argument package.class#field takes a form identical to that of the @see argument, except that the member must be a static field. These values of these constants are also displayed on the Constant Field Values @ http://docs.oracle.com/javase/7/docs/api/constant-values.html page. @version version-text Adds a "Version" subheading with the specified version-text to the generated docs when the -version option is used. This tag is intended to hold the current version number of the software that this code is part of (as opposed to @since, which holds the version number where this code was introduced). The version-text has no special internal structure. To see where the version tag can be used, see Where Tags Can Be Used. A doc comment may contain multiple @version tags. If it makes sense, you can specify one version number per @version tag or multiple ver‐ sion numbers 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 writing @version tags @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html#@version. Where Tags Can Be Used The following sections describe where the tags can be used. Note that these tags can be used in all doc comments: @see, @since, @deprecated, {@link}, {@linkplain}, and {@docroot}. 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 over‐ view.html). Like in any other documentation comments, these tags must appear after the main description. NOTE - The {@link} tag has a bug in overview documents in version 1.2 -- the text appears properly but has no link. The {@docRoot} tag does not currently work in overview documents. Overview Tags o @see o @since o @author o @version o {@link} o {@linkplain} o {@docRoot} 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 or pack‐ age-info.java). The @serial tag can only be used here with the include or exclude argument. Package Tags o @see o @since o @serial o @author o @version o {@link} o {@linkplain} o {@docRoot} Class and Interface Documentation Tags The following are tags that can appear in the documentation comment for a class or interface. The @serial tag can only be used here with the include or exclude argument. Class/Interface Tags o @see o @since o @deprecated o @serial o @author o @version o {@link} o {@linkplain} o {@docRoot} 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 1.13, 06/08/06 * @see java.awt.BaseWindow * @see java.awt.Button */ class Window extends BaseWindow { ... } Field Documentation Tags The following are the tags that can appear in Field Tags o @see o @since o @deprecated o @serial o @serialField o {@link} o {@linkplain} o {@docRoot} o {@value} 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, except for @return, which cannot appear in a constructor, and {@inheritDoc}, which has certain restrictions. The @serialData tag can only be used in the doc comment for certain serial‐ ization methods. Method/Constructor Tags o @see o @since o @deprecated o @param o @return o @throws and @exception o @serialData o {@link} o {@linkplain} o {@inheritDoc} o {@docRoot} 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) { ... } OPTIONS The javadoc tool uses doclets to determine its output. The Javadoc tool uses the default standard doclet unless a custom doclet is specified with the -doclet option. The Javadoc tool 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 -header -private -author -help -protected -bootclasspath -helpfile -public -bottom -J -quiet -breakiterator -keywords -serialwarn -charset -link -source -classpath -linkoffline -sourcepath -d -linksource -sourcetab -docencoding -locale -splitindex -docfilessubdirs -nocomment -stylesheetfile -doclet -nodeprecated -subpackages -docletpath -nodeprecatedlist -tag -doctitle -nohelp -taglet -encoding -noindex -tagletpath -exclude -nonavbar -top -excludedocfilessub‐ -noqualifier -title dir -nosince -use -extdirs -notimestamp -verbose -footer -notree -version -group -overview -windowtitle -package Options shown in italic are the Javadoc core options, which are provided by the front end of the Javadoc tool and are available to all doclets. The standard doclet itself provides the non-italic options. 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 current directory. While you can use any name you want for filename and place it any‐ where you want for path, a typical thing to do is to name it over‐ view.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 over‐ view 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 com‐ mand 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 -doclet‐ path option. For example, to call the MIF doclet, use: -doclet com.sun.tools.doclets.mif.MIFDoclet For full, working examples of running a particular doclet, see the MIF Doclet documentation @ http://java.sun.com/j2se/javadoc/mifdoclet/docs/mifdoclet.html. -docletpath classpathlist Specifies the path to the doclet starting class file (specified with the -doclet option) and any jar files it depends on. If the starting class file is in a jar file, then this specifies the path to that jar file, as shown in the example below. You can specify an absolute path or a path relative to the current directory. If classpathlist contains multiple paths or jar files, they should be separated with a colon (:) on Solaris and a semi-colon (;) on Win‐ dows. This option is not necessary if the doclet starting class is already in the search path. Example of path to jar file that contains the starting doclet class file. Notice the jar filename is included. -docletpath /home/user/mifdoclet/lib/mifdoclet.jar Example of path to starting doclet class file. Notice the class filename is omitted. -docletpath /home/user/mifdoclet/classes/com/sun/tools/doclets/mif/ For full, working examples of running a particular doclet, see the MIF Doclet documentation @ http://java.sun.com/j2se/javadoc/mifdoclet/docs/mifdoclet.html. -1.1 This feature has been removed from Javadoc 1.4. There is no replacement for it. This option created documentation with the appearance and functionality of documentation generated by Javadoc 1.1 (it never supported nested classes). If you need this option, use Javadoc 1.2 or 1.3 instead. -source release Specifies the version of source code accepted. The following values for release are allowed: o 1.5 - javadoc accepts code containing generics and other language features introduced in JDK 1.5. The compiler defaults to the 1.5 behavior if the -source flag is not used. o 1.4 - javadoc accepts code containing assertions, which were introduced in JDK 1.4. o 1.3 - javadoc does not support assertions, generics, or other language features introduced after JDK 1.3. Use the value of release corresponding to that used when compiling the code with javac. -sourcepath sourcepathlist Specifies the search paths for finding source files (.java) when passing package names or -subpackages into the javadoc command. The sourcepathlist can contain multiple paths by separating them with a colon (:). The Javadoc tool will search in all subdirectories of the specified paths. Note that this option is not only used to locate the source files being documented, but also to find source files that are not being documented but whose comments are inher‐ ited by the source files being documented. 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 -class‐ path). 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 subdirecto‐ ries) 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 docu‐ ment 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 (:). The Javadoc tool will search in all subdirectories of the specified paths. Follow the instructions in class path @ http://docs.oracle.com/javase/7/docs/tech‐ notes/tools/index.html#general documentation for specifying class‐ pathlist. If -sourcepath is omitted, the Javadoc tool uses -classpath to find the source files as well as class files (for backward compatibil‐ ity). 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 spec‐ ify: % javadoc -classpath /home/user/lib -sourcepath /home/user/src com.mypackage As with other tools, if you do not specify -classpath, the Javadoc tool uses the CLASSPATH environment variable, if it is set. If both are not set, the Javadoc tool searches for classes from the current directory. For an in-depth description of how the Javadoc tool uses -classpath to find user classes as it relates to extension classes and boot‐ strap classes, see How Classes Are Found @ http://docs.oracle.com/javase/7/docs/technotes/tools/finding‐ classes.html. As a special convenience, a class path element containing a base‐ name of * is considered equivalent to specifying a list of all the files in the directory with the extension .jar or .JAR (a Java pro‐ gram cannot tell the difference between the two invocations). For example, if directory foo contains a.jar and b.JAR, then the class path element foo/* is expanded to a A.jar:b.JAR, except that the order of jar files is unspecified. All jar files in the speci‐ fied directory, even hidden ones, are included in the list. A classpath entry consisting simply of * expands to a list of all the jar files in the current directory. The CLASSPATH environment vari‐ able, where defined, will be similarly expanded. Any classpath wildcard expansion occurs before the Java virtual machine is started -- no Java program will ever see unexpanded wildcards except by querying the environment. For example; by invoking Sys‐ tem.getenv("CLASSPATH"). -subpackages package1:package2:... Generates documentation from source files in the specified packages and recursively in their subpackages. This option is useful when adding new subpackages to the source code, as they are automati‐ cally included. Each package argument is any top-level subpackage (such as java) or fully qualified package (such as javax.swing) that does not need to contain source files. Arguments are separated by colons (on all operating systmes). Wildcards are not needed or allowed. Use -sourcepath to specify where to find the packages. This option is smart about not processing source files that are in the source tree but do not belong to the packages, as described at processing of source files. For example: % javadoc -d docs -sourcepath /home/user/src -subpackages java:javax.swing This command generates documentation for packages named "java" and "javax.swing" and all their subpackages. You can use -subpackages in conjunction with -exclude to exclude specific packages. -exclude packagename1:packagename2:... Unconditionally excludes the specified packages and their subpack‐ ages from the list formed by -subpackages. It excludes those pack‐ ages even if they would otherwise be included by some previous or later -subpackages option. For example: % javadoc -sourcepath /home/user/src -subpackages java -exclude java.net:java.lang would include java.io, java.util, and java.math (among others), but would exclude packages rooted at java.net and java.lang. Notice this excludes java.lang.ref, a subpackage of java.lang). -bootclasspath classpathlist Specifies the paths where the boot classes reside. These are nomi‐ nally the Java platform classes. The bootclasspath is part of the search path the Javadoc tool will use to look up source and class files. See How Classes Are Found @ http://docs.oracle.com/javase/7/docs/technotes/tools/finding‐ classes.html#srcfiles. 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 the Javadoc tool 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 mes‐ sages specifying the number of milliseconds to parse each java source file. -quiet Shuts off non-error and non-warning messages, leaving only the warnings and errors appear, making them easier to view. Also sup‐ presses the version string. -breakiterator Uses the internationalized sentence boundary of java.text.BreakIt‐ erator @ http://docs.oracle.com/javase/7/docs/api/java/text/BreakItera‐ tor.html to determine the end of the first sentence for English (all other locales already use BreakIterator), rather than an Eng‐ lish language, locale-specific algorithm. By first sentence, we mean the first sentence in the main description of a package, class or member. This sentence is copied to the package, class or member summary, and to the alphabetic index. From JDK 1.2 forward, the BreakIterator class is already used to determine the end of sentence for all languages but English. There‐ fore, the -breakiterator option has no effect except for English from 1.2 forward. English has its own default algorithm: o English default sentence-break algorithm - Stops at a period fol‐ lowed by a space or a HTML block tag, such as <P>. o Breakiterator sentence-break algorithm - In general, stops at a period, question mark or exclamation mark followed by a space if the next word starts with a capital letter. This is meant to han‐ dle most abbreviations (such as "The serial no. is valid", but won't handle "Mr. Smith"). Doesn't stop at HTML tags or sentences that begin with numbers or symbols. Stops at the last period in "../filename", even if embedded in an HTML tag. NOTE: We have removed from 1.5.0 the breakiterator warning messages that were in 1.4.x and have left the default sentence-break algorithm unchanged. That is, the -breakiterator option is not the default in 1.5.0, nor do we expect it to become the default. This is a reversal from our former intention that the default would change in the "next major release" (1.5.0). This means if you have not modified your source code to eliminate the breakiterator warnings in 1.4.x, then you don't have to do anything, and the warnings go away starting with 1.5.0. The reason for this reversal is because any benefit to having breakiterator become the default would be outweighed by the incompati‐ ble source change it would require. We regret any extra work and con‐ fusion this has caused. -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 documenta‐ tion. 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. Also see -docencoding and -charset. -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 exam‐ ple, 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) (The version number of the standard doclet appears in its output stream.) Options Provided by the Standard Doclet -d directory Specifies the destination directory where javadoc saves the gener‐ ated 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. As of 1.4, the destination directory is automatically created when javadoc is run. For example, the following generates the documentation for the package com.mypackage 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 us 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 implementa‐ tion. If a method uses String in its implementation but does not take a string as an argument or return a string, that is not con‐ sidered 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 the Javadoc tool 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, the Javadoc tool uses the value of -doctitle for this option. % javadoc -windowtitle "Java SE Platform" com.mypackage -doctitle title Specifies the title to be placed near the top of the overview sum‐ mary file. The title will be placed as a centered, level-one head‐ ing directly beneath the upper navigation bar. The title may con‐ tain 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(TM)" 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 naviga‐ tion 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>v1.4" 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 naviga‐ tion 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. -top Specifies the text to be placed at the top of each output file. -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 quo‐ tation marks within text may have to be escaped. -link extdocURL Creates links to existing javadoc-generated documentation of exter‐ nal referenced classes. It takes one argument: o extdocURL is the absolute or relative URL of the directory con‐ taining the external javadoc-generated documentation you want to link to. Examples are shown below. The package-list file must be found in this directory (otherwise, use -linkoffline). The Javadoc tool reads the package names from the package-list file and then links to those packages at that URL. When the Javadoc tool is run, the extdocURL value is copied literally into the <A HREF> links that are created. Therefore, extdocURL must be the URL to the directory, not to a file. You can use an absolute link for extdocURL to enable your docs to link to a document on any website, or can use a relative link to link only to a relative location. If relative, the value you pass in should be the relative path from the destination directory (specified with -d) to the directory containing the packages being linked to. When specifying an absolute link you normally use an http: link. However, if you want to link to a file system that has no web server, you can use a file: link -- however, do this only if everyone wanting to access the generated documentation shares the same file system. In all cases, and on all operating systems, you should use a for‐ ward slash as the separator, whether the URL is absolute or rela‐ tive, and "http:" or "file:" based (as specified in the URL Memo @ http://www.ietf.org/rfc/rfc1738.txt). Absolute http: based link: -link http://<host>/<directory>/<directory>/.../<name> Absolute file: based link: -link file://<host>/<directory>/<directory>/.../<name> Relative link: -link <directory>/<directory>/.../<name> You can specify multiple -link options in a given javadoc run to link to multiple documents. Choosing between -linkoffline and -link: Use -link: o when using a relative path to the external API document, or o when using an absolute URL to the external API document, if your shell allows a program to open a connection to that URL for read‐ ing. Use -linkoffline: o when using an absolute URL to the external API document, if your shell does not allow a program to open a connection to that URL for reading. This can occur if you are behind a firewall and the document you want to link to is on the other side. Example using absolute links to the external docs - Let us say you want to link to the java.lang, java.io and other Java Platform pack‐ ages at http://docs.oracle.com/javase/7/docs/api/ @ http://docs.oracle.com/javase/7/docs/api/. The following command gen‐ erates documentation for the package com.mypackage with links to the Java SE Platform packages. The generated documentation will contain links to the Object class, for example, in the class trees. (Other options, such as -sourcepath and -d, are not shown.) % javadoc -link http://docs.oracle.com/javase/7/docs/api/ com.mypackage Example using relative links to the external docs - Let us say you have two packages whose docs are generated in different runs of the Javadoc tool, and those docs are separated by a relative path. In this example, the packages are com.apipackage, an API, and com.spipackage, an SPI (Service Provide Interface). You want the documentation to reside in docs/api/com/apipackage and docs/spi/com/spipackage. Assum‐ ing the API package documentation is already generated, and that docs is the current directory, you would document the SPI package with links to the API documentation by running: % javadoc -d ./spi -link ../api com.spipackage Notice the -link argument is relative to the destination directory (docs/spi). Details - The -link option enables you to link to classes referenced to by your code but not 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.* documenta‐ tion on http://java.sun.com. 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, the Javadoc tool does not create links to documentation for external references, because it does not know if or where that documentation exists.) This option can create links in several places in the generated docu‐ mentation. Another use is 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. How a Class Must be Referenced - For a link to an external referenced class to actually appear (and not just its text label), the class must be referenced in the following 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.io.File can be referenced: o In any kind of import statement: by wildcard import, import explicitly by name, or automatically import for java.lang.*. For example, this would suffice: import java.io.*; In 1.3.x and 1.2.x, only an explicit import by name works -- a wildcard import statement does not work, nor does the automatic import java.lang.*. o In a declaration: void foo(File f) {} The reference and be in the return type or parameter type of a method, constructor, field, class or interface, or in an imple‐ ments, extends or throws statement. An important corollary is that when you use the -link option, there may be many links that unintentionally do not appear due to this con‐ straint. (The text would appear without a hypertext link.) You can detect these by the warnings they emit. 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 pack‐ age-list, which is generated by the Javadoc tool, 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. In the ear‐ lier example, the Javadoc tool looks for a file named package-list at the given URL, reads in the package names and then links to those packages at that URL. For example, the package list for the Java SE 6 API is located at http://docs.oracle.com/javase/7/docs/api/package-list @ http://docs.oracle.com/javase/7/docs/api/package-list. and starts 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, 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, the Javadoc tool 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 extdocURL. In order for there to be no broken links, all of the documentation for the external references must exist at the specified URLs. The Javadoc tool will not check that these pages exist -- only that the pack‐ age-list exists. Multiple Links - You can supply multiple -link options to link to any number of external generated documents. Javadoc 1.2 has a known bug which prevents you from supplying more than one -link command. This was 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 gen‐ erated. In other words, if package-list does not exist for either doc‐ ument, when you run the Javadoc tool on the first document, the pack‐ age-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 exter‐ nal links. The Javadoc tool prints a warning if a needed external package-list file does not exist. -linkoffline extdocURL packagelistLoc This option is a variation of -link; they both create links to javadoc-generated documentation for external referenced classes. Use the -linkoffline option when linking to a document on the web when the Javadoc tool itself is "offline" -- that is, it cannot access the document through a web connection. More specifically, use -linkoffline if the external document's package-list file is not accessible or does not exist at the extdocURL location but does exist at a different location, which can be specified by packageListLoc (typically local). Thus, if extdocURL is accessible only on the World Wide Web, -linkoffline removes the constraint that the Javadoc tool have a web connection when generating the documentation. Another use is as a "hack" to update docs: After you have run javadoc on a full set of packages, then you can run javadoc again on onlya smaller set of changed packages, so that the updated files can be inserted back into the original set. Examples are given below. The -linkoffline option takes two arguments -- the first for the string to be embedded in the <a href> links, the second telling it where to find package-list: o extdocURL is the absolute or relative URL of the directory con‐ taining the external javadoc-generated documentation you want to link to. If relative, the value should be the relative path from the destination directory (specified with -d) to the root of the packages being linked to. For more details, see extdocURL in the -link option. o packagelistLoc is the path or URL 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 rela‐ tive. If relative, make it relative to the current directory from where javadoc was run. Do not include the package-list filename. You can specify multiple -linkoffline options in a given javadoc run. (Prior to 1.2.2, it could be specified only once.) Example using absolute links to the external docs - Let us say you want to link to the java.lang, java.io and other Java SE Platform packages at http://docs.oracle.com/javase/7/docs/api/, but your shell does not have web access. You could open the package-list file in a browser at http://docs.oracle.com/javase/7/docs/api/package-list @ http://docs.oracle.com/javase/7/docs/api/package-list, save it to a local directory, and point to this local copy with the second argu‐ ment, packagelistLoc. In this example, the package list file has been saved to the current directory "." . The following command generates documentation for the package com.mypackage with links to the Java SE Platform packages. The generated documentation will contain links to the Object class, for example, in the class trees. (Other necessary options, such as -sourcepath, are not shown.) % javadoc -linkoffline http://docs.oracle.com/javase/7/docs/api/ . com.mypackage Example using relative links to the external docs - It's not very com‐ mon to use -linkoffline with relative paths, for the simple reason that -link usually suffices. When using -linkoffline, the package-list file is generally local, and when using relative links, the file you are linking to is also generally local. So it is usually unnecessary to give a different path for the two arguments to -linkoffline. When the two arguments are identical, you can use -link. See the -link rel‐ ative example. Manually Creating a package-list File - 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. An example would be the previous case where the package list for com.spipackage did not exist when com.apipackage was first generated. This technique is useful when you need to gener‐ ate documentation that links to new external documentation whose pack‐ age names you know, but which is not yet published. This is also a way of creating package-list files for packages generated with Javadoc 1.0 or 1.1, where package-list files were not generated. Likewise, two companies can share their unpublished package-list files, enabling them to release their cross-linked documentation simultaneously. Linking to Multiple Documents - You can 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 \ ... Updating docs - Another use for -linkoffline 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 declarations. If you were to add, remove or change any declarations from the source code, then broken links could show up in the index, package tree, inherited member lists, use page, and other places. First, you create a new destination directory (call it update) for this new small run. Let us say the original destination directory was named html. In the simplest example, cd to the parent of html. Set the first argument of -linkoffline to the current directory "." and set the second argument to the relative path to html, where it can find package-list, and pass in only the package names of the packages you want to update: % javadoc -d update -linkoffline . html com.mypackage When the Javadoc tool is done, copy these generated class pages in update/com/package (not the overview or index), over the original files in html/com/package. -linksource Creates an HTML version of each source file (with line numbers) and adds links to them from the standard HTML documentation. Links are created for classes, interfaces, constructors, methods and fields whose declarations are in a source file. Otherwise, links are not created, such as for default constructors and generated classes. This option exposes all private implementation details in the included source files, including private classes, private fields, and the bodies of private methods, regardless of the -public, -package, -protected and -private options. Unless you also use the -private option, not all private classes or interfaces will neces‐ sarily be accessible via links. Each link appears on the name of the identifier in its declaration. For example, the link to the source code of the Button class would be on the word "Button": public class Button extends Component implements Accessible and the link to the source code of the getLabel() method in the Button class would be on the word "getLabel": public String getLabel() -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 differ‐ ent -group option. The groups appear on the page in the order spec‐ ified 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. o groupheading can be any text, and can include white space. This text is placed in the table heading for the group. o 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 wild‐ card 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 pack‐ ages 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 docu‐ mentation. This does what -nodeprecatedlist does, plus it does not generate any deprecated API throughout the rest of the documenta‐ tion. 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 depre‐ cated APIs (deprecated-list.html) and the link in the navigation bar to that page. (However, javadoc continues to generate the dep‐ recated 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 pages from the generated docs. These are the pages you reach using the "Tree" button in the navi‐ gation bar. 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, the Javadoc tool automatically creates a help file help-doc.html that is hard-coded in the Javadoc tool. This option enables you to override this default. The filename can be any name and is not restricted to help-doc.html -- the Javadoc tool 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, the Javadoc tool automatically creates a stylesheet file stylesheet.css that is hard-coded in the Javadoc tool. 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 doc‐ ument default serializable fields and writeExternal methods. -charset name Specifies the HTML character set for this document. The name should be a preferred MIME name as given in the IANA Registry @ http://www.iana.org/assignments/character-sets. 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 @ http://www.w3.org/TR/REC-html40/charset.html#h-5.2.2. (4197265 and 4137321) Also see -encoding and -docencoding. -docencoding name Specifies the encoding of the generated HTML files. The name should be a preferred MIME name as given in the IANA Registry @ http://www.iana.org/assignments/character-sets. If you omit this option but use -encoding, then the encoding of the generated HTML files is determined by -encoding. Example: % javadoc -docencoding "ISO-8859-1" mypackage Also see -encoding and -charset. -keywords Adds HTML meta keyword tags to the generated file for each class. These tags can help the page be found by search engines that look for meta tags. (Most search engines that search the entire Internet do not look at meta tags, because pages can misuse them; but search engines offered by companies that confine their search to their own website can benefit by looking at meta tags.) The meta tags include the fully qualified name of the class and the unqualified names of the fields and methods. Constructors are not included because they are identical to the class name. For example, the class String starts with these keywords: <META NAME="keywords" CONTENT="java.lang.String class"> <META NAME="keywords" CONTENT="CASE_INSENSITIVE_ORDER"> <META NAME="keywords" CONTENT="length()"> <META NAME="keywords" CONTENT="charAt()"> -tag tagname:Xaoptcmf:"taghead" Enables the Javadoc tool to interpret a simple, one-argument custom block tag @tagname in doc comments. So the Javadoc tool can "spell-check" tag names, it is important to include a -tag option for every custom tag that is present in the source code, disabling (with X) those that are not being output in the current run. The colon (:) is always the separator. To use a colon in tagname, see Use of Colon in Tag Name. The -tag option outputs the tag's heading taghead in bold, followed on the next line by the text from its single argument, as shown in the example below. Like any block tag, this argument's text can contain inline tags, which are also interpreted. The output is sim‐ ilar to standard one-argument tags, such as @return and @author. Omitting taghead causes tagname to appear as the heading. Placement of tags - The Xaoptcmf part of the argument determines where in the source code the tag is allowed to be placed, and whether the tag can be disabled (using X). You can supply either a, to allow the tag in all places, or any combination of the other letters: X (disable tag) a (all) o (overview) p (packages) t (types, that is classes and interfaces) c (constructors) m (methods) f (fields) Examples of single tags - An example of a tag option for a tag that can be used anywhere in the source code is: -tag todo:a:"To Do:" If you wanted @todo to be used only with constructors, methods and fields, you would use: -tag todo:cmf:"To Do:" Notice the last colon (:) above is not a parameter separator, but is part of the heading text (as shown below). You would use either tag option for source code that contains the tag @todo, such as: @todo The documentation for this method needs work. Use of Colon in Tag Name - A colon can be used in a tag name if it is escaped with a backslash. For this doc comment: /** * @ejb:bean */ use this tag option: -tag ejb\\:bean:a:"EJB Bean:" Spell-checking tag names (Disabling tags) - Some developers put custom tags in the source code that they don't always want to out‐ put. In these cases, it is important to list all tags that are present in the source code, enabling the ones you want to output and disabling the ones you don't want to output. The presence of X disables the tag, while its absence enables the tag. This gives the Javadoc tool enough information to know if a tag it encounters is unknown, probably the results of a typo or a misspelling. It prints a warning in these cases. You can add X to the placement values already present, so that when you want to enable the tag, you can simply delete the X. For exam‐ ple, if @todo is a tag that you want to suppress on output, you would use: -tag todo:Xcmf:"To Do:" or, if you'd rather keep it simple: -tag todo:X The syntax -tag todo:X works even if @todo is defined by a taglet. Order of tags - The order of the -tag (and -taglet) options deter‐ mine the order the tags are output. You can mix the custom tags with the standard tags to intersperse them. The tag options for standard tags are placeholders only for determining the order -- they take only the standard tag's name. (Subheadings for standard tags cannot be altered.) This is illustrated in the following exam‐ ple. If -tag is missing, then the position of -taglet determines its order. If they are both present, then whichever appears last on the command line determines its order. (This happens because the tags and taglets are processed in the order that they appear on the com‐ mand line. For example, if -taglet and -tag both have the name "todo", the one that appears last on the command line will deter‐ mine its order. Example of a complete set of tags - This example inserts "To Do" after "Parameters" and before "Throws" in the output. By using "X", it also specifies that @example is a tag that might be encountered in the source code that should not be output during this run. Notice that if you use @argfile, you can put the tags on separate lines in an argument file like this (no line continuation charac‐ ters needed): -tag param -tag return -tag todo:a:"To Do:" -tag throws -tag see -tag example:X When javadoc parses the doc comments, any tag encountered that is neither a standard tag nor passed in with -tag or -taglet is con‐ sidered unknown, and a warning is thrown. The standard tags are initially stored internally in a list in their default order. Whenever -tag options are used, those tags get appended to this list -- standard tags are moved from their default position. Therefore, if a -tag option is omitted for a standard tag, it remains in its default position. Avoiding Conflicts - If you want to slice out your own namespace, you can use a dot-separated naming convention similar to that used for packages: com.mycompany.todo. Oracle will continue to create standard tags whose names do not contain dots. Any tag you create will override the behavior of a tag by the same name defined by Oracle. In other words, if you create a tag or taglet @todo, it will always have the same behavior you define, even if Oracle later creates a standard tag of the same name. Annotations vs. Javadoc Tags - In general, if the markup you want to add is intended to affect or produce documentation, it should probably be a javadoc tag; otherwise, it should be an annotation. See Comparing Annotations and Javadoc Tags @ http://www.oracle.com/technetwork/java/javase/documenta‐ tion/index-137868.html#annotations< You can also create more complex block tags, or custom inline tags with the -taglet option. -taglet class Specifies the class file that starts the taglet used in generating the documentation for that tag. Use the fully-qualified name for class. This taglet also defines the number of text arguments that the custom tag has. The taglet accepts those arguments, processes them, and generates the output. For extensive documentation with example taglets, see: o Taglet Overview @ http://docs.oracle.com/javase/7/docs/tech‐ notes/guides/javadoc/taglet/overview.html Taglets are useful for block or inline tags. They can have any number of arguments and implement custom behavior, such as making text bold, formatting bullets, writing out the text to a file, or starting other processes. Taglets can only determine where a tag should appear and in what form. All other decisions are made by the doclet. So a taglet cannot do things such as remove a class name from the list of included classes. However, it can execute side effects, such as printing the tag's text to a file or triggering another process. Use the -tagletpath option to specify the path to the taglet. Here is an example that inserts the "To Do" taglet after "Parameters" and ahead of "Throws" in the generated pages: -taglet com.sun.tools.doclets.ToDoTaglet -tagletpath /home/taglets -tag return -tag param -tag todo -tag throws -tag see Alternatively, you can use the -taglet option in place of its -tag option, but that may be harder to read. -tagletpath tagletpathlist Specifies the search paths for finding taglet class files (.class). The tagletpathlist can contain multiple paths by separating them with a colon (:). The Javadoc tool will search in all subdirecto‐ ries of the specified paths. -docfilessubdirs Enables deep copying of "doc-files" directories. In other words, subdirectories and all contents are recursively copied to the des‐ tination. For example, the directory doc-files/example/images and all its contents would now be copied. There is also an option to exclude subdirectories. -excludedocfilessubdir name1:name2... Excludes any "doc-files" subdirectories with the given names. This prevents the copying of SCCS and other source-code-control subdi‐ rectories. -noqualifier all | packagename1:packagename2:... Omits qualifying package name from ahead of class names in output. The argument to -noqualifier is either "all" (all package quali‐ fiers are omitted) or a colon-separate list of packages, with wild‐ cards, to be removed as qualifiers. The package name is removed from places where class or interface names appear. The following example omits all package qualifiers: -noqualifier all The following example omits "java.lang" and "java.io" package qual‐ ifiers: -noqualifier java.lang:java.io The following example omits package qualifiers starting with "java", and "com.sun" subpackages (but not "javax"): -noqualifier java.*:com.sun.* Where a package qualifier would appear due to the above behavior, the name can be suitably shortened -- see How a name is displayed. This rule is in effect whether or not -noqualifier is used. -notimestamp Suppresses the timestamp, which is hidden in an HTML comment in the generated HTML near the top of each page. Useful when you want to run javadoc on two source bases and diff them, as it prevents time‐ stamps from causing a diff (which would otherwise be a diff on every page). The timestamp includes the javadoc version number, and currently looks like this: <!-- Generated by javadoc (build 1.5.0_01) on Thu Apr 02 14:04:52 IST 2009 --> -nocomment Suppress the entire comment body, including the main description and all tags, generating only declarations. This option enables re-using source files originally intended for a different purpose, to produce skeleton HTML documentation at the early stages of a new project. -sourcetab tabLength Specify the number of spaces each tab takes up in the source. COMMAND LINE ARGUMENT FILES To shorten or simplify the javadoc command line, you can specify one or more files that themselves contain arguments to the javadoc command (except -J options). This enables you to create javadoc commands of any length on any operating system. An argument file can include javac options and source filenames in any combination. The arguments within a file can be space-separated or new‐ line-separated. If a filename contains embedded spaces, put the whole filename in double quotes. Filenames within an argument file are relative to the current directory, not the location of the argument file. Wildcards (*) are not allowed in these lists (such as for specifying *.java). Use of the '@' character to recursively interpret files is not supported. The -J options are not sup‐ ported because they are passed to the launcher, which does not support argument files. When executing javadoc, pass in the path and name of each argument file with the '@' leading character. When javadoc encounters an argument beginning with the character `@', it expands the contents of that file into the argument list. Example - Single Arg File You could use a single argument file named "argfile" to hold all Javadoc arguments: % javadoc @argfile This argument file could contain the contents of both files shown in the next example. Example - Two Arg Files You can create two argument files -- one