Groups > comp.lang.java.programmer > #31595

Abuse of AssertionError?

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From	Eric Sosman <esosman@comcast-dot-net.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Abuse of AssertionError?
Date	Tue, 21 Apr 2015 08:44:10 -0400
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     A recent thread on `assert' prompts me to ask for opinions
about something I've been doing that may not be entirely kosher.
Now and then I write a method that computes and returns a value,
but whose computation relies on a data structure built elsewhere.
If that data structure is messed up the computation may go off
the rails, and I'd like to detect that.

     For example, here's a (paraphrase of a) method that finds the
marginal income tax bracket for a stated income level:

	private static double marginalTaxRate(double income) {
	    income = Math.max(income, 0);
	    for (int i = BRACKETS.length; --i >= 0; ) {
	        if (income >= BRACKETS[i].floor) {
	            return BRACKETS[i].rate;
	        }
	    }
	    // What goes here?
	}

If everything has been set up correctly, the BRACKETS are arranged
in increasing order by their income floors and the floor of the
zero'th BRACKET is zero, so the `if' will eventually be satisfied
and the method will return a value.  But if something's amiss the
loop will run to completion -- and then the compiler will complain
about falling off the end of a value-returning method.

     My solution has been to write

	throw new AssertionError("BUG!");

where the comment stands, and I'd like others to comment on whether
this is an acceptable practice, or suggest a better approach.

     Red herrings that are of little interest:

     - Using `double' for monetary calculations.  I solemnly swear that
       in the context from which this example was adapted, `double' is
       an entirely suitable choice.  Sue me.

     - Rewriting the loop to remove the `i >= 0' test would silence
       the compiler's complaint.  But then if the BRACKETS were messed
       up I'd eventually get ArrayIndexOutOfBoundsException instead --
       even less informative than AssertionError, IMHO.

     Thoughts?  Ideas?

-- 
esosman@comcast-dot-net.invalid
"Don't be afraid of work. Make work afraid of you." -- TLM

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Thread

Abuse of AssertionError? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-04-21 08:44 -0400
  Re: Abuse of AssertionError? Jerry Stuckle <jstucklex@attglobal.net> - 2015-04-21 10:21 -0400
    Re: Abuse of AssertionError? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-04-21 11:21 -0400
      Re: Abuse of AssertionError? Jerry Stuckle <jstucklex@attglobal.net> - 2015-04-21 11:31 -0400
  Re: Abuse of AssertionError? j4n bur53 <janburse@fastmail.fm> - 2015-04-21 16:59 +0200
    Re: Abuse of AssertionError? Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-04-21 11:26 -0400
  Re: Abuse of AssertionError? Thomas Richter <thor@math.tu-berlin.de> - 2015-04-21 17:05 +0200

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