Hi. > > [...] > >>> Cases such as this would fall in the "illegal argument" category. > >>> Thus: > >>> > >>> throw new OutOfRangeException(index, 0, parameters.length); > >>> > >>> or, to get a more detailed message, > >>> > >>> OutOfRangeException e = new OutOfRangeException(index, 0, > >>> parameters.length); > >>> e.addMessage(INDEX, index); > >>> throw e; > >>> > >>> > >>> Of course, "OutOfRangeException" cannot inherit from both > >>> "IllegalArgumentException" and "IndexOutOfBoundsException"... > >> I thought about that, but would prefer to throw > >> ArrayIndexOutOfBoundsException because that is really what is going > >> on and I would prefer to throw the standard exception. Ideally, I > >> would like to throw that with a message reporting the value and the > >> length of the array. So, there are three choices: > >> > >> 0) throw AIOB with no message > >> 1) subclass and throw with localized message - my suggestion above > >> 2) OutOfRangeException > >> > >> I like 1) the best and since we have decided to deprecate the > >> MathRuntimeException, note that it applies to all of the other > >> standard exceptions generated by MathRuntimeException's createXxx > >> methods that have not yet been subclassed. I think we should follow > >> the generally accepted practice to favor standard exceptions, so > >> that means we are going to have to create wrappers for all that we > >> use. I am willing to help with this. In this case, I will go ahead > >> and add the MathArrayIndexOutOfBoundsException that will be an > >> ArrayIndexOutOfBoundsException if others are OK with this. Note > >> that doing this will allow us to handle situations where IAE is not > >> appropriate (essentially why AIOB does not itself extend IAE). > > As I understand it, AIOB is a low-level exception that is thrown by the JVM > > checking an array access: > > ---CUT--- > > i = 3; > > double a = arr[i]; // <--- can throw AIOB > > ---CUT--- > > > > However, I don't see how a user code can be similar to this: When you check > > the index in your above code, you didn't try to access the array yet. You've > > detected that it won't work because the index value is "out of range", thus, > > "illegal". > > When we are about to access an array, we can perform the check. We > can either just allow the JVM to throw the RTE (essentially my > option 0) above) or provide some more context info to the user (my > option 1) or throw an entirely different exception (option 2). It > is good to throw some kind of AIOB when that is in fact what is > going on, as it provides more context info than just "something is > out of range" (OutOfRangeException).
As shown above, you can add as many items of context information as you want with the exception context. The example I've suggested above will create a message that will print something like: OutOfRangeException: 3 out of [0, 2] range: index (3) I find this quite clear; but we can even add another "LocalizedFormats" like "ARRAY_INDEX" if you really need the above to read: OutOfRangeException: 3 out of [0, 2] range: array index (3) However, the crux of my point is that the "array" part is an implementation detail. A user should not care that a sequence of data is stored in an array of primitives or in a "List" or a CM's "RealVector". The real info is that the index used to access the data must fall within a range; if not, it is "out of range". Then, what I was saying in the previous post is that we should not throw AIOB because we are not the JVM. In Java, that exception is a *result* of "calling" the [] operator. Your test happens before calling it; and an "OutOfRangeException" is as accurate as necessary but not more (so as not to leak about the internals of a class). Gilles --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
