Le 23/12/2010 14:31, Gilles Sadowski a écrit :
> Hello.
>
> While replacing, in "RealVectorFormat", the last occurrence of the old
> "o.a.c.math.MathRuntimeException" in package "linear", I stumbled upon the
> following:
>
> 1. "RealVectorFormat" inherits from the standard Java class "Format".
> 2. That "Format" class has a method
> public Object parseObject(String source) throws ParseException
> where "ParseException" is a _checked_ exception.
> 3. Some unit tests for "RealVectorFormat" call that base class method,
> although the actual parsing code (in "RealVectorFormat") never generates
> that exception.
>
> [Side-note: the old to-be-deprecated "MathRuntimeException" contains a method
> public static ParseException createParseException(...)
> Thus, we had the inconsistency that a class dedicated to creating unchecked
> exceptions has a method that create a checked exception!]
>
> We can solve the problem with the unit tests by readily calling the "parse"
> method in the "RealVectorFormat" (instead of "parseObject" in "Format").
>
> Then when "RealVectorFormat" fails to parse a string, it should throw a new
> (not yet existing) "MathParseException" that will inherit from the new
> "o.a.c.math.exception.MathRuntimeException".
>
> But that will lead to the problem that some user could write
> Format fmt = new RealVectorFormat();
> at which point he has only access to "parseObject". He is thus obliged
> to enclose the call in try/catch block and will be tempted to feel safe by
> catching "ParseException":
> try {
> ArrayRealVector v = (ArrayRealVector) fmt.parseObject(str);
> } catch (ParseException e) {
> // Do something...
> }
> But the catch is actually useless because a failed parsing will throw a
> "MathParseException" runtime exception!
>
> To avoid this case, I was wondering whether we could, instead of having
> public class RealVectorFormat extends CompositeFormat {
> // ...
> }
> have
> public class RealVectorFormat {
> CompositeFormat compositeFormat;
>
> // ...
> }
> without any ill side-effects.
So you basically prevent users from doing
Format fmt = new RealVectorFormat();
Also if there is still a CompositeFormat inside which still extends
java.util.Format, what happens when it cannot parse ? Is the checked
exception caught and wrapped into an unchecked one ?
Luc
>
>
> Regards,
> Gilles
>
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