Explaining NULL and Empty to your 6-year old?

Question

I'm thinking in terms of Objects here. I think it's important to simplify ideas. If you can explain this to a 6-year old, you can teach new programmers the difference.

I'm thinking that a cookie object would be apropos:

public class Cookie {
  public string flavor {get; set; }
  public int numberOfCrumbs { get; set; }
}

Answer 1

Empty would be , looking into a Cookie Jar, and finding nothing.

NULL would be not having a Cookie Jar.

Answer 2

Typically, null refers to an unknown value, so if you had phone number, they'd know their classmates have a phone number, but not necessarily what it was.

Answer 3

NULL is a marker for invalid like a blinking warning light or perhaps like a period at the end of a sentence showing that the thought/sequence is complete.

Empty just means that there is nothing in a container, but it could contain an object if you wanted to put something in it.

Answer 4

I think NULL means "I don't know"

Even if there is a cookie jar, if you can see inside, and count 0, then you know there are none.

If you are asked how many cookies, and you see the jar and it is not possible to look in the cookie jar, then you say "I don't know".

Answer 5

Empty = Air

Null = Vacancy

Answer 6

I'm a Common Lisp programmer, you insensitive clod!

(They're identical, by definition, in Common Lisp.)

Answer 7

Empty means the cookie jar you're pointing to is empty. Null means you're not pointing to anything.

So if you're pointing to a cookie jar and ask a kid "What are the contents of the cookie jar that I'm pointing to?" then you'll get the answer that it's empty. If you ask that question without pointing to anything, well, then it depends on what language you're asking in. If your native tongue is Java, the kid gets confused and upset; if you're from a country where C++ is spoken, the kid crashes.

(And God help you if you accidentally tell them to interpret the refrigerator as a cookie jar.)