When empty lists are serialized or deserialized through web services, they can be converted into nulls by the Jackson and Jersey libraries. Therefore, your code must be able to handle getting back a null property instead of an empty list. Also, an empty list passed into the web services api can be converted into a null. Therefore, the api treats them as equivalent.

Examples illustrating checks for null properties are included in the WsDevClient class in the sample client provided with the SDK.