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From "Anton Avtamonov" <anton.avtamo...@gmail.com>
Subject Re: [classlib] Exception throwing compatibility: java.util.Scanner
Date Thu, 06 Jul 2006 13:20:53 GMT
Hi Richard,

Very good example.
You are right, spec says nothing about invalid radix processing for
nextInt(). RI behavior just proves they have no guard check. However
useRadix() produces IAE for the invalid radix and the sound of logic
says that IAE is a proper reaction for wrong radix in any method with
radix. Looks like a bug in RI for me...

Don't beat me please :-), but I would suggest two approaches:
- either no checks for radix, so that underlying algorithm does or
doesn't produce some exceptions
- implement guard check and produce IAE.

I believe that right solution is the second one - produce IAE -
however it potentailly results in less compatibility with RI.

-- 
Anton Avtamonov,
Intel Middleware Products Division

On 7/6/06, Richard Liang <richard.liangyx@gmail.com> wrote:
> Hello All,
>
> When I'm trying to implement Scanner.nextInt(int radix), I met a problem.
>
> As we all know, Character.MIN_RADIX equals 2 and Character.MAX_RADIX
> equals 36, so the parameter radix can not less than 2 or greater than
> 36, Otherwise that parameter is illegal.
>
> But on RI, when the parameter radix is illegal, there are different
> kinds of Exception thrown.
>
>    * If the parameter is less than 0 or greater than 36, RI throws a
>      StringIndexOutOfBoundsException. Obviously this exception depends
>      an RI's implementation.
>    * If the parameter equals 1, RI throws an InputMismatchException
>      with an additional information "The radix 1 is less than the
>      Character.MIN_RADIX".
>    * If the parameter equals 0, RI throws a
>      java.util.regex.PatternSyntaxException whose constructor has three
>      parameters. And the parameters depends on RI's implementation,
>      that makes me can not follow RI.
>
> And nothing is documented in the spec. Shall I follow RI's behavior?
> Thanks a lot.
>
> Here is the test case to demo this issue.
>
> public void test_nextIntI(){
>       Scanner s = new Scanner("123 456");
>
>       try {
>            s.nextInt(-1);
>            fail("Should throw StringIndexOutOfBoundsException");
>        } catch (StringIndexOutOfBoundsException e) {
>            // Expected
>        }
>        try {
>            s.nextInt(0);
>            fail("Should throw PatternSyntaxException");
>        } catch (PatternSyntaxException e) {
>            // Expected
>        }
>        try {
>            s.nextInt(1);
>            fail("Should throw InputMismatchException");
>        } catch (InputMismatchException e) {
>            // Expected
>        }
>        try {
>            s.nextInt(40);
>            fail("Should throw StringIndexOutOfBoundsException");
>        } catch (StringIndexOutOfBoundsException e) {
>            // Expected
>        }
> }
>
> --
> Richard Liang
> China Software Development Lab, IBM
>
>
>

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