Re: Design Questions about static factory classes
On Sun, 23 May 2010, Lew wrote:
Arne Vajh?j wrote:
Bad user input is not really exceptional enough to justify an exception.
Tom Anderson wrote:
I disagree. We've had arguments about the proper use of exceptions on
this newsgroup before, so i [sic] recognise that this is a matter where
opinions vary, but exceptions seem like a perfectly acceptable option
for dealing with bad user input to me. They might not be the right
solution in every situation, but they are an option that can be considered.
And usually rejected.
Read /Effective Java/ (2nd ed.), "Item 57: Use exceptions only for
exceptional conditions", and the rest of section 9.
No.
Part of the problem with exceptions is that they are expensive relative
to conditionals.
True. I wouldn't worry about that in input validation code of this kind
unless i had a profiler screaming at me that it was a problem.
Hmm. Do profilers track the amount of time the JVM spends handling
exceptions?
The other part in this case is that you expect bad inputs - they aren't
exceptional conditions at all.
Your style is your style, tom, and you are absolutely correct to suggest that
one should consider all options. But the design purpose of exceptions is to
deal with out-of-line conditions, and input validation is squarely in line.
I don't agree that bad input is not an exceptional condition; i wonder if
you are confusing 'exceptional' and 'unlikely' or 'unexpected'. I agree
that validating input must be done inline, but not that dealing with
invalid input must be. I'd say exactly the opposite, in fact.
tom
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