On 01/13/2011 11:41 PM, David M. Lloyd wrote:
On 01/13/2011 04:31 PM, Rémi Forax wrote:
On 01/13/2011 11:11 PM, Brian Goetz wrote:
<rathole>
I disagree with Tom here. We have *already* made the billion dollar
mistake, and we can't eliminate that headache (but we can provide
easier access to aspirin.) Java developers are *constantly* writing
methods like the suggested carpet-sweeping nonNull() to work around
this (and some of the Objects methods already do this, like
hashCode()). If I had to guess how many times this exact method had
been written across all the Java code in the world, I would be quite
surprised if its common logarithm were less than 4.
</rathole>
I disagree.
Propagating null is rare if your API doesn't allow to take null as
argument.
The only place where you need to propagate null is when you output
something like in Swing or
in the presentation tier of a webapp.
Otherwise propagating null is a mistake because it adds layers between
the bug and it's appearance.
I disagree with your disagreement. :)
A null value very commonly means "not found". Consider such examples
as Map.get(). Trying to pretend like null doesn't exist is silly, and
trying to pretend that people don't write such methods and count on
this functionality is equally silly. If you don't think people should
be using null, say so on your blog; don't enforce your opinion on
others through core API changes.
I was not clear. I don't pretend that null doesn't exist.
Carpet sweeping is not a good idea. As you said, null is used as return
value. I have no problem with that.
I just pretend that the developer has to put an "if" here and not call a
kind of black magic
function that will only work with 10 lines examples.
I for one like null; I think it is damned handy. And I think
propagating it is just fine so long as it is documented as a part of
the contract of the method. That's an education issue, not a language
issue.
By documentation, do you mean you use @Nullable and a null typecheker.
In that case I agree with you,
otherwise it's rare to see the documentation of a field saying that it
can be null.
So when you modify something you have to follow the reference backward
from usage sites.
I hate to do that.
Rémi
