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From Niall Pemberton <niall.pember...@gmail.com>
Subject Re: [lang] LANG-510
Date Fri, 05 Mar 2010 10:40:59 GMT
On Fri, Mar 5, 2010 at 9:32 AM, Henri Yandell <flamefew@gmail.com> wrote:
> Thinking further on moving StringUtils to CharSequence, I'd like to
> take the String left(String, int) method as an example. It depends on
> substring(int, int), so is entirely possibly to move over to
> subSequence(int, int).
>
> Hypothetical new method:
>
>    CharSequence left(CharSequence, int)
>
> The downside here is that users currently storing this in a String are
> going to have to cast. Generics to the rescue.
>
>    <T extends CharSequence> T left(T, int)
>
> This hits two problems:
>
> 1) EMPTY is returned when the int is less than 0; EMPTY is a String and not T.

>From CharSequence's subSequence() javadoc "if start == end  then an
empty sequence is returned". So you could do:

     return (T)str.subSequence(0, 0);

Niall


> 2) subSequence returns CharSequence and not T.
>
> I could add a wrapper method to make Strings nicer:
>
>    public static String left(String str, int len) {
>        if (str == null) {
>            return null;
>        }
>        return left( (CharSequence) str, len).toString();
>    }
>
> But that doesn't help the StringBuffer/StrBuilder/StringBuilder user;
> they still get a sucky API.
>
> Am I missing anything obvious here, or should I give up the ghost on
> trying to take these methods to CharSequence APIs?
>
> Hen

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