When I first had a look at the wrapper Boolean data type in Java a funny thought came to my mind about the tri-state nature of a boolean (Why null becomes a possible value?). Later applied the thought to any other data type which is nullable and got funny analogies. Since Object Oriented Programming was related directly to real world, I came up with the following analogy.
Every morning you get your newspaper delivered at your doorstep. The paper boy rings the bell and leaves the paper at your doorstep. Let us assume that the door bell is the function call and newspaper is the object you receive. What happens if you wont get the newspaper delivered?; quite obvious, the paper boy either won’t arrive or will come to your doorstep and communicate why the paper is not delivered.
What would happen if instead of the above scenario the paper boy arrives at your doorstep and delivers a null newspaper? You must receive the newspaper & assert that it is not null and decide to do some other activity, else your day ends abruptly because a null pointer is thrown when you tried to read the newspaper. Now let us not limit this to just newspaper, what about the need to worry about nulls every where? Would not you be driven crazy that you will have to worry about null mails, null phone calls, null water bottles?
This is what happens with many Java programmers where there is some point in their life they had dealt with a sticky, messy null pointer exception caused by some one who had made use of null for a boolean as a logic flow alternative to the true and false state. More worse is the SQL boolean data type having unknown and null as possible values.
So much of code has been written with guard clauses to prevent these nasty null pointer exceptions from getting in and eventually cost 3 extra lines of code in almost all critical business logic methods. Lately I have seen a positive trend among peers in the way we treat nulls. I have seen many consiously avoiding nulls and replacing them with empty objects, Null object pattern or special instances to handle ambiguities. When we move to newer (I would say newly adopted) languages I believe null will cease to exist.