You recover Javadoc comments in classes, interfaces, operations, and attributes during reverse engineering. Javadoc comments are reverse engineered only if they exist in the source code.
The Reverse Javadoc Comments feature is very useful for round-trip engineering: you keep Javadoc comments during reverse engineering and you can regenerate the code with preserved Javadoc comments. The generation process generates object comments compliant with Javadoc
For more information on the generation of Javadoc comments, see Javadoc Comments Generation and Reverse Engineering.