Often, documentation takes the form of early requirements specifications, user's guides, or line by line comments within the actual source code. Good documentation allow much easier use, maintenance, and reuse of finished software products.
Documentation can also serve as a guide for software engineers as they create software.
Java programmers already use javac and java to create and execute programs, now it's time to add the API Document Generator to your toolbox. Javadoc creates code documentation that is easy to read and understand. The HTML pages it generates are easy to post on Web sites and can be easily distributed to a software team. Many programmers often neglect documentation, but Javadoc provides an opportunity to create very professional looking API specifications that require little overhead to create. In addition, documentation is produced directly from source code files.