Some IDEs provide support for generating HTML from Javadocs automatically, but this can also be achieved using the command line:

javadoc tool

The most basic usage of the tool is the line below:

javadoc JavaFile.java

That will generate HTML from the Javadoc comments in JavaFile.java.

A more practical use of the command line tool, that will recursively read all Java files in [source-directory], create documentation for the [package.name] and all sub-packages, and also place the generated HTML in the [docs-directory] is:

javadoc -d [docs-directory] -subpackages -sourcepath [source-directory] [package.name]