Hi
I think I found an incomplete explanation in the book "OCP Oracle Certified Professional Java SE 11 by Jeanne Boyarsky and Scott Selikoff".
On page 368 of the book the following code is given:
The explanation given for the "sleep" method is:
The next method,sleep, does not compile because it is missing parentheses, (), for method arguments.
While this is true it would not result in it being able to compile. It must also be provided a body enclosed in braces or be marked
abstract.