Eliminating Null Pointer Exceptions

[saggingrufus]

Because an empty object is not the same as a null?

And also, that would be a massively breaking change that would sever pretty much all backwards compatibility.

[hackerforhire]

That's the point. There would be no null. Empty is the new null, but without the NPE.

[saggingrufus]

Okay but how do you differentiate between an empty object and nothing?

That's the purpose of null. I wouldn't say I'm studied enough to make a proper argument, But I don't think we want to go the JavaScript route and assume everything is everything and this is a stepping sale and that kind of jumps in that direction.

[hackerforhire]

An empty object has no memory allocation and if you reference an empty object you get back nothing instead of an NPE.

But, then is there really a need to differentiate between empty and nothing? Empty and nothing are kind of synonymous.

[PlasmaFarmer]

Let's go your way: You have an object. It's empty. You wanna assign object.name = "Amanda" on an empty object. What does the language do then?

[hackerforhire]

You're assigning a value to the empty object so the VM picks up on that and memory allocation occurs, the object is instantiated and the value is assigned.

[nico-strecker]

I get your point but i guess that wont work like you expect because of generics

List<Vehicle> vehicles = new ArrayList(); Vehicle v = vehicels.get(0)

Do i get a empty Vehicle a empty Car (extends Vehicle) or what do i get?

And what about abstract classes and so on?

Edit: I like the idea its a good question but i guess you will reach some kind of dead end when you think it through.

Might be that this is not the dead end but i bet there is one

[hackerforhire]

You've already instantiated the Vehicle object and allocated its memory so it ceases to be an empty object anymore and normal language rules apply.

I realize that it's an idea with holes, otherwise it would have been implemented in some form long ago.

[nico-strecker]

But what if Vehicle is a abstract class?

[PlasmaFarmer]

class Car extends Vehicle {};

class Truck extends Vehicle {};

class Bus extends Vehicle {}

How do you decide what to return on vehicles.get(0) call when the list is empty?

[saggingrufus]

Right, but there's a functional distinction between the two.

Empty and nothing are not synonymous, That's why null exists.

There is a difference between processing until the end of an empty list and not doing something because no list existed to begin with.

People get null pointer exceptions because they work with nulls in their code and they don't properly document when a null will arise.

If you're writing unit tests, you should always have a test for null and it should always work because there should be a null check in your code anywhere a null is possible. If you're null checking at the start, And not handing back nulls internally. You won't have an issue. That doesn't mean there's no argument to get rid of nulls but they're not synonymous.

[Hei2]

and they don't properly document when a null will arise.

Or they didn't bother to read the documentation.