What is null in Java?

Question

What is null?

Is null an instance of anything?

What set does null belong to?

How is it represented in the me

Answer 1

An interesting way to see null in java in my opinion is to see it as something that DOES NOT denote an absence of information but simply as a literal value that can be assigned to a reference of any type. If you think about it if it denoted absence of information then for a1==a2 to be true doesn't make sense (in case they were both assigned a value of null) as they could really could be pointing to ANY object (we simply don't know what objects they should be pointing to)... By the way null == null returns true in java. If java e.g. would be like SQL:1999 then null==null would return unknown (a boolean value in SQL:1999 can take three values : true,false and unknown but in practise unknown is implemented as null in real systems)... http://en.wikipedia.org/wiki/SQL