> > assertEquals("Test ü  and more",  
> DecoderUtil.decodeEncodedWords("Test
> > =?ISO-8859-1?Q?=FC_?= =?ISO-8859-1?Q?and_more?="));
>
> Coincidentally the same problem has been reported yesterday by Wim
> Jongman. Funny how bugs like this can somehow remain undetected for
> years and then show up all of a sudden..
>
This then qualifies as a Schroedinbug: http://catb.org/~esr/jargon/html/S/schroedinbug.html

> > After this fix there is only one space between "ü" and "and",  
> which I think
> > is not correct (but I'm not sure).
>
> No I think one space would be correct, see MIME4J-104.
>
My bad! Sorry.

> > Proposed Solution:
> >
> > Replace "indexOf" by Regex matching, like so:
> > [...]
>
> I'm afraid that would reintroduce MIME4J-104..
>

If you are interested I could write a regex based version which will  
not reintroduce the double space bug.
I'ld use the regex to extract charset, encoding and encoded string in  
one go. I think it will be at least as fast as the current method.
However, java.util.regex requires Java 1.4, if that's a no-go I won't  
bother.
Thanks for your quick response.