Major Description
The docs for floorDiv() and floorMod() (both the int & long methods) say things like:
Finds q such that a = q b + r with 0 <= r < b if b > 0 and b < r <= 0 if b > 0.
That latter clause is probably supposed to be "if b < 0" - this should be clarified since (AFAICT) the whole point of these functions is to change the behavior from native ops when b is negative, or maybe when a*b is negative, but I'm not really sure which.
As an aside, it would be great to add similar methods when a is a float/double, because Java's mod/div operators support float/double types too.