Re: How to tell caller of an error if you cant change the signature of a method

Owen Jacobson <>
Mon, 14 Apr 2008 09:52:33 -0700 (PDT)
On Apr 14, 11:36 am, Royan <> wrote:

OK So let me summarize: There are three options:

1) Wrap checked exceptions and rethrow some sort of RuntimeException
that would contain some detailed message of an error
2) Retrieve some predefined, most likely constant value of type
String[] that any class can access and understand what has happened.
3) Create an exception handling method and handle all exceptional
cases there

Am I correct that there are no more solutions to the problem (assuming
we cannot change interface)?

If so I vote for option 2, because option 1 and 3 is evil.


3) Exception handler method that is used within utility method seems
to be even worse. First because caller should (in our case this is the
method where a call to readStream occurs) always receive information
about the success or failure of "readStrings()" operation. If we grab
every checked exception and return null indicating an error we will
never be able to properly separate view from model. For instance if
FileNotFoundException has occurred, I may want to visually tell user
of an error, but if i grab that exception an return null I will not be
able to understand if it was a FileNotFoundException or IOException or
whatever exception I will always receive null.

The point I was making was to implement 3 by having the caller pass in
its desired exception handling strategy (via the constructor in my
example). It is equivalent to wrapping the method in an application-
specific try/catch block; the difference is in how it's implemented,
not in the functionality it provides.

So, for your case, you would pass in a handler (exception callback, if
you will) that knows to display a "file not found" dialog on


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