Funny. For some reason, it always seemed like the *ultimate* in degenerative cases to have an object with no method bodies/default method bodies. Having said that, I've used it all over the place due to its usefulness!

Let's say I wanted to have a conversation with someone. I call them over to my desk, and start talking. If they show up, everything is fine. If I talk to thin air, my coworkers are going to question my sanity.

The absence of an object when its presence is required is an exceptional situation. It means you can't do the work you planned on because one of your prerequisites is not met.

Martin Fowler suggests a "Special Case" object. That makes me laugh for 2 reasons:

1. Instead of repetitive null-checking, you have repetitive derivations. The problem didn't go away, it just takes more typing and artifacts to express it. This approach cascades all the way down every single inheritance hierarchy and could have just been solved with a simple null-check.

2. What will NullCustomer.getPlan() do if not throw an exception? Will it return a NullPlan, which in turn returns other derivations?

At some point, you have to address the absence of your target object. If that is not done on the *first* operation, in my opinion that violates the Principle of Least Surprise.

Updated the article to remove the obvious bias.

Except for optional activities,  I would agree with Bryan.

Here here

Having null be a first class object in the language would be even better!

Ah ruby

Conditionals are a code smell. Null/missing object pattern is a very nice way to eliminate a certain subset of said smell.

Great reminder: The Null Pattern is a Good Thing....

@Jeremy G: Conditionals are a code smell? Really? How long, then, until code is a code smell? ;)

Like Joe, I am of the opinion that a nullo is good for an optional object. I just think of it as the nullo instance being the default state of the field rather than null being the default (almost like it's a value type rather than a ref type). Providing a nullo for non-optional dependencies seems dangerous to me.

Yes, it's a great thing. I did a series of posts on it (geekswithblogs.net/.../null-object-pattern.aspx and geekswithblogs.net/.../null-object-pattern-follow-up.aspx as well.

Nullability really should be a first class language citizen where the . operator is lifted so that calling a method or property on a null object simply returns null as well.