To go with my previous entery about pointers "The Fishbowl" has his/hers own entry on the same topic.. both inspired by Jeremy's adventures with Java.

The part I really want to reference is this section:

1. Before you start writing a method, decide whether it will ever return null. Document this decision in the @return section of the method's Javadoc.
2. Never have a method return null unless there's a really good reason for it.
3. If your method returns an array or a collection, there's no reason to ever return null. Return an empty array or collection instead.
4. If you have a situation where null is a valid value for a variable, you can make use of the Introduce Null Object refactoring, to make the behaviour explicit.

That's very good advice.