[3190] in java-interest
Re: Better way to handle user-defined exception
daemon@ATHENA.MIT.EDU (Thomas Ball)
Thu Nov 2 20:12:12 1995
Date: Thu, 2 Nov 1995 14:18:17 -0800
From: Thomas.Ball@Eng.Sun.COM (Thomas Ball)
To: edith@pencom.com
Cc: java-interest@java.Eng.Sun.COM
> The following "code" will throw a user-defined exception if
>
> user entered a number < 0 or > 10.
>
> class abc
> {
>
> public static void main(String args[]) throws
> outOfRangeException
> {
> try
> {
> int x = new Integer(args[0]).intValue();
> if (x < 0 || x > 10)
> throw new outOfRangeException();
> }
> catch (NumberFormatException e)
> {
> printErrMesg("Wrong format");
> }
> catch (outOfRangeException e)
> {
> printErrMesg("Out of range input");
> }
> }
>
> static void printErrMesg(String mesg)
> {
> System.out.println(mesg);
> }
> }
>
>
> class outOfRangeException extends Exception
> {
> outOfRangeException()
> {}
> }
>
>
> From the user friendly point of view, I don't want to show user
> a thread stack if an out of range number is entered. I just
> want to print out a simple error message. I am forced to
> create a dummy exception subclass, outOfRangeException, because
> I want to catch the exception in the main program.
You are not forced to do anything -- the decision whether to use or
not use user-defined exceptions is yours to make. I wouldn't use it
in your example above.
> You might argue I can just simply do
> if (x<0 || x>10)
> System.out.println ("Out of Range Input.");
>
> but that's not what I want. I would like to have a centralize
> place (method printErrMesg()) to handle error message.
Then just do:
if (x<0 || x>10)
printErrMessage("Out of Range Input.");
> Does anyone has a better way to handle this? Creating a dummy
> exception is kind of ugly and confused.........
I think your confusion stems from not fully understanding how to use
exceptions -- it's a new concept for many programmers, so please don't
take my comment as a criticism. Exceptions are useful for separating
correct program execution from error handling -- it makes for easier to
read code if used properly, as well as fewer ignored error conditions.
Several recent C++ books discuss exception handling for people who are
new to the concept -- can someone else recommend such a book?
Tom Ball
Java Products Group
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