If a comment is out of date spend a few seconds to update or remove it. Don't leave it there to confuse the next person.
// The integer ID of the customer // Initially set to -1 to show it has not yet been loaded with data String customerId = null;
Update it before it confuses the next person who takes comments at face value:
// The String ID of the customer // When null it means “not yet loaded with data” String customerId = null;