If you are using an IDE such as Eclipse to do your business, you can use a quick weezard to do your dirty work for you.
In Eclipse, click Project > Generate Javadoc…
Select the packages you want to include.
Specify the visibility level you want to include.
In the Destination text field, specify the location where you want the docs to go. Click Next.
Tweak the documentation options if you want—usually it is best to leave them all selected.
Specify a different stylesheet if you like, using the CSS classes as shown previously. Click Finish.