Javadoc (originally cased as JavaDoc) is a documentation generator created by Sun Microsystems for the Java language (now owned by Oracle Corporation) for generating API documentation in HTML format from Java source code. The HTML format is used to add the convenience of being able to hyperlink related documents together.
Contents
The "doc comments" format used by Javadoc is the de facto industry standard for documenting Java classes. Some IDEs, such as Netbeans and Eclipse, automatically generate Javadoc HTML. Many file editors assist the user in producing Javadoc source and use the Javadoc info as internal references for the programmer.
Javadoc also provides an API for creating doclets and taglets, which allows you to analyze the structure of a Java application. This is how JDiff can generate reports of what changed between two versions of an API.
History
Javadoc was an early Java language documentation generator. Prior to the use of documentation generators it was customary to use technical writers who would typically write only standalone documentation for the software, but it was much harder to keep this documentation in sync with the software itself.
Javadoc has been used by Java since the first release, and is usually updated on every new release of the Java Development Kit.
Structure of a Javadoc comment
A Javadoc comment is set off from code by standard multi-line comment tags /* and */. The opening tag (called begin-comment delimiter), has an extra asterisk, as in /**.
- The first paragraph is a description of the method documented.
- Following the description are a varying number of descriptive tags, signifying:
- The parameters of the method (
@param) - What the method returns (
@return) - Any exceptions the method may throw (
@throws) - Other less-common tags such as
@see(a "see also" tag)
- The parameters of the method (
Overview of Javadoc
The basic structure of writing document comments is to embed them inside /** ... */. The Javadoc is written next to the items without any separating newline. Note that any import statements must precede the class declaration. The class declaration usually contains:
For methods there is (1) a short, concise, one line description to explain what the item does. This is followed by (2) a longer description that may span multiple paragraphs. The details can be explained in full here. This section, marked in brackets [], is optional. Lastly, there is (3) a tag section to list the accepted input arguments and return values of the method. Note that all of the Javadoc is treated as HTML so the multiple paragraph sections are separated by a "<p>" paragraph break tag.
Variables are documented similarly to methods with the exception that part (3) is omitted. Here the variable contains only the short description:
Note that it is not recommended to define multiple variables in a single documentation comment. This is because Javadoc reads each variable and places them separately to the generated HTML page with the same documentation comment that is copied for all fields.
Instead, it is recommended to write and document each variable separately:
Some of the available Javadoc tags are listed in the table below:
Example
An example of Javadoc to document a method follows. Notice that spacing and number of characters in this example are as conventions state.