How is the manual/development document written in Java?

Because the files we get or give to others in Java development are generally class files and do not give source files, it is necessary to write a simple and understandable manual.

PS: @param int[] arr will have a warning that you can delete int [].

Parsing document annotations with tools: Javadoc tools

javadoc-d Directory-d-author-version Arraytool.java

Sometimes you get an error: You can't find a public or protected class that can be documented--and add a common to the class.

How is the manual/development document written in Java?