Printing RPG game character properties
Is anything unclear about this code? 


The purpose of this code is unclear.


  Do I break any good-programming rules?


Some bad practices that immediately jump into the eye:


Formatting is horrible
The parameterless constructor of Warrior is pointless and can be safely omitted
Methods with empty bodies, such as fight and levelUp in Human should at least have a comment explaining why the implementation is left empty
showAbility is poorly named:


None of the attributes are abilities: name is certainly not an ability, and the other fields are questionable too
"show" is a bit ambiguous. Show where? In a pop-up, maybe? I'd use the word "print" instead.


Maybe printStats would be better.
It's probably not a big concern for your programming exercise, but for the record, print statements inside a program are generally frowned upon. The preferred way is to use a logging framework instead. (Again, this is just for the record, since you asked about bad practices.)


Instead of Warrior inheriting from Human,
consider using interfaces.
For example you could have Warrior and Mage interfaces,
so that you can have mighty mage-warriors.
With inheritance this would be impossible.
Using interfaces will lead to a more extensible design.