> Only bad experience I remember from Java was the int/Integer primitive/object issue and boxing.

Heh, I once had to work in a code base that used an `Integer premiumDefenseLevel`. It contained the level of premium defense a player had purchased, or null if the player didn't have any levels of premium defense purchased in the recent times.

This was in fact annoying to remove, because a 0 after a 1 was treated differently than a null some time for advertisement reasons: Someone who had bought premium defense in the past is more likely to re-buy than someone who didn't, so they are pestered with ads. But it eventually turned into a neat little domain object.