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Groups > comp.lang.java.programmer > #36696

Re: How to handle same sanity checks

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Cecil Westerhof <Cecil@decebal.nl> wrote:
> In my code I have several methods that start with:
>     if ((n < MIN_VAL) || (n > MAX_VAL)) {
>         throw new InvalidParameterException(String.format(ERROR_N, n));
>     }
> That is not really DRY.
> I could write a method like:
>     private void checkN(n) {
>         if ((n < MIN_VAL) || (n > MAX_VAL)) {
>             throw new InvalidParameterException(String.format(ERROR_N, n));
>         }
>     }
> And then replace all the checks with a call to checkN. But then the
> exception is generated in the method checkN instead of the method that
> has a wrong parameter.

I would not worry about where the exception gets thrown from, as long
as the call-stack includes the "real culprit".

If you really want it thrown at the call-site, there are these slightly
more verbose variants:

Let checkN() *return* the exception (or null if all was ok), then:
   for (Exception e=checkN(...);e!=null;) { throw e; }
Yes, it's weird to use a "for" here, but "if" doesn't allow ad-hoc
declaration of the Exception var. If you declare "e" ahead, then it
becomes: (not much better, imho)
   Exception e; if ((e=checkN(...))!=null) { throw e; }
(You could also combine this with Martin Gregorie's suggestions.)

Another approach is, to wrap creation of the exception and the check
separately:
   private Exception invalPar(...) {
      return new InvalidParameterException(String.format( ... ));
   }
   private boolean checkN(...) { return ((n < MIN_VAL) || (n > MAX_VAL)); }

and at call-site:

   if (checkN(...)) { throw invalPar(...); }

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Thread

How to handle same sanity checks Cecil Westerhof <Cecil@decebal.nl> - 2017-06-22 11:10 +0200
  Re: How to handle same sanity checks Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-22 10:27 +0000
    Re: How to handle same sanity checks Cecil Westerhof <Cecil@decebal.nl> - 2017-06-22 13:21 +0200
    Re: How to handle same sanity checks Cecil Westerhof <Cecil@decebal.nl> - 2017-06-23 06:51 +0200
    Re: How to handle same sanity checks Robert Klemme <shortcutter@googlemail.com> - 2017-06-24 12:06 +0200
      Re: How to handle same sanity checks Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-24 10:33 +0000
        Re: How to handle same sanity checks Robert Klemme <shortcutter@googlemail.com> - 2017-06-24 16:46 +0200
          Re: How to handle same sanity checks Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-24 19:37 +0000
  Re: How to handle same sanity checks Andreas Leitgeb <avl@logic.at> - 2017-06-22 11:26 +0000
    Re: How to handle same sanity checks Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-22 07:44 -0400
      Re: How to handle same sanity checks Andreas Leitgeb <avl@logic.at> - 2017-06-22 12:30 +0000
  Re: How to handle same sanity checks Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-22 07:40 -0400
    Re: How to handle same sanity checks v_borchert@despammed.com (Volker Borchert) - 2017-06-22 18:33 +0000
      Re: How to handle same sanity checks Cecil Westerhof <Cecil@decebal.nl> - 2017-06-23 06:48 +0200
        Re: How to handle same sanity checks Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-23 09:57 -0400
          Re: How to handle same sanity checks Cecil Westerhof <Cecil@decebal.nl> - 2017-06-23 16:31 +0200
            Re: How to handle same sanity checks Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-23 17:21 +0000
              Re: How to handle same sanity checks Eric Douglas <e.d.programmer@gmail.com> - 2017-06-26 05:21 -0700
                Re: How to handle same sanity checks Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-26 13:34 +0000
                Re: How to handle same sanity checks Martin Gregorie <martin@address-in-sig.invalid> - 2017-06-26 15:22 +0000
        Re: How to handle same sanity checks Arne Vajhøj <arne@vajhoej.dk> - 2017-06-25 22:55 -0400
  Re: How to handle same sanity checks Marcel Mueller <news.5.maazl@spamgourmet.org> - 2017-06-22 23:07 +0200
  Re: How to handle same sanity checks Joerg Meier <joergmmeier@arcor.de> - 2017-06-25 09:52 +0200
  Re: How to handle same sanity checks Robert Klemme <shortcutter@googlemail.com> - 2017-06-25 12:31 +0200
    Re: How to handle same sanity checks Arne Vajhøj <arne@vajhoej.dk> - 2017-06-25 14:23 -0400
      Style police (Was: Re: How to handle same sanity checks) Eric Sosman <esosman@comcast-dot-net.invalid> - 2017-06-25 17:28 -0400
        Re: Style police (Was: Re: How to handle same sanity checks) Arne Vajhøj <arne@vajhoej.dk> - 2017-06-25 19:14 -0400
        Re: Style police (Was: Re: How to handle same sanity checks) Arne Vajhøj <arne@vajhoej.dk> - 2017-06-25 19:19 -0400
          Re: Style police (Was: Re: How to handle same sanity checks) Robert Klemme <shortcutter@googlemail.com> - 2017-06-26 23:34 +0200

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