Generating Javadoc 
You can generate Javadoc for all compilation public parts of the development components (DCs), if the defined public parts contain any of the following Java entities:
Java Class
Java Package or
Java Package Tree
In addition to the standard information of a Javadoc, the generated Javadoc also contains information about public parts and DCs. In addition, you can link your Javadoc against SAP's API Javadoc.
The generation itself can be performed using:
Ant tasks
Command line tool
Build infrastructure extension (collects the *.jdar files from the referenced public parts)
Directly during DC build
The generated Javadoc contains documentation for all classes (including inner classes) and packages published by the public part. By default, only classes and members with a public or protected modifier are included.
The result of the Javadoc generation is stored in the output folder of the public part gen/default/<public-part-name> in the subfolder doc/java of your project.
Depending on the selected output format, a ZIP archive named javadoc.zip or an additional archive with the file extension .JDAR can be found. The name of the .JDAR file is derived from the DC/public part name in the same way as for the corresponding public part archive.
If a javadoc.zip is available for a referenced compilation public part, the Developer Studio automatically attaches that archive as a Javadoc source to a DC project. For example, the Javadoc View automatically appears in a Java editor, if you position the mouse cursor above or near a symbol in the source code.
Note that this mechanism works both for local development configurations as well as for centrally managed tracks. In the latter case, the javadoc.zip is downloaded from the Component Build Service (CBS) together with the public part archives.
The Javadoc archives (javadoc.zip, *.jdar) are contained in the public part archive (.ppa file) of a public part and can be downloaded from the CBS Web UI. Furthermore, Javadoc content is automatically assembled into SCAs by Change Management Service (CMS) and can subsequently be transported to other tracks.
For more information about downloading files from CBS, see Downloading DC Archives.
You have to enable the Javadoc generation to be able to use it.
For more information, see Enabling Javadoc Generation.
You can change the default options for Javadoc generation. For more information, see Configuring Javadoc Generation.
For more information, see Generating Javadoc for Large Software Units.