What is the Javadoc?
The source code of java programs is “self-documented”.
Most classes, methods and attributes are described by some short docstring to explain their purpose. This documentation can be visualised as a user-friendly webpage: the Javadoc or API (for Application Programming Interface).
The API is a precious ressource for users and developers willing to develop custom scripts or programs. It lists all available functions for a given class, and give information on what type of parameter they expect and return.
Most scijava-projects API are listed on the scijava javadocs.
And more particulary for
The ImageJ1 API
The diagram below depicts the relation between the different classes composing ImageJ1.