"A random value from 0 to 1 is being coerced to the integer value 0. You probably want to multiple the random value by something else before coercing it to an integer, or use the Random.nextInt(n) method."
That's about as good an explanation as you'd get from anyone.
The way I see it is this. Simple bugs like this happen because _human beings are flawed._ All it takes is a momentary lapse of concentration and you've put the cast in the wrong place in a method you don't write a test for because you're in a hurry, and all it's doing is generating a random number with a standard API so why bother? (Or it's something you wouldn't normally even test for, like assuming something is re-entrant when it isn't)
We're inevitably going to make a certain number of mistakes a day, and it's our duty to put systems into place that catch those mistakes before they cause any more damage than they should.