Java and SQL : return null or throw exception?

Question

This is another debated subject, but this time i am searching only for the simple and documented answers. The scenario :

Let\'s assume the following method:

Answer 1

Null Object Pattern is a design pattern where you always return an object to avoid NPE:s and any null checks in your code. In your case this means that instead of returning null, return an empty Hashtable instead.

The reasoning is that since it's a collection and your other code will access it as such, it won't break down if you return an empty collection; it won't be iterated through, it won't contain anything surprising, it wont cause NPE:s to be thrown and whatnot.

To be precise, a Null Object is a special implementation of a class/interface which does absolutely nothing and thus has no side effects of any kind. Because of its nature of not being null using it will make your code cleaner since when you know that you'll always get an object from your method calls no matter what happens inside the method you don't even have to check for nulls nor make code reacting to them! Because Null Object doesn't do anything, you can even have them as singletons just lying around and thus save memory by doing that.