HashRoaringSet uses two conditions to decide whether it will switch to bitmap:
1. Number of elements (threshold).
2. Difference between the maximum and minimum value of the elements it has seen so far (universe size).

It starts using the hashSet and when the number of elements has reached the threshold it checks whether `maxValue-minvalue < universe size`. If both conditions are met, it changes state and it should call the onSwitchToRoaring method. However, at the moment the onSwitchToRoaring method is called even when the state does not change.