Ok, well, still you didn't provide important info. I had to find it on my own and looks like you are talking about Elfos' code, more or less?
Uppon config load it stores the info
public void add(double weight, E result)
{
if (weight <= 0) return;
total += weight;
map.put(total, result);
}
public E next()
{
double value = random.nextDouble() * total;
return map.ceilingEntry(value).getValue();
}
So, the next return 0.0 - 1.0 * total . But still, I don't see any "chance calculation" over the code, else that's the chance itself? I guess?