"the fact that the argument is an ActionListener"

should be

"the fact that the argument is an ActionEvent"

In the sentence 

> The fact that this listener is an ActionListener, the fact that the
> callback method is named actionPerformed, and the fact that the 
> argument is an ActionListener are all implied for any argument to 
> addActionListener.

I wondered whether "the argument" should refer to the argument
of the callback method, so that its implied type would be
"ActionEvent" instead of ActionListener.

[Yes, that was a typo. Fixed.]