Re: how to trim() a String only at the right side?

From:
Silvio <silvio@internet.com>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 26 Sep 2013 12:14:23 +0200
Message-ID:
<52440900$0$16003$e4fe514c@news.xs4all.nl>
On 09/25/2013 10:31 PM, markspace wrote:

On 9/25/2013 6:55 AM, Andreas Leitgeb wrote:

I'd need to trim only *trailing* whitespace off a String (or
StringBuilder)
while preserving leading white space. Furthermore (unlike trim()), I'd
only
strip exact \u0020 chars, no other control chars.

I could code a while-loop to search for last non-\u0020 char position
and then
extract the approriate substring (or delete() the spaces), but if
there is a
more elegant solution that I've missed in the javadocs, then I'd be
glad about
a hint.

PS: no need to code out any solutions involving explicit loops.
PPS: target is Java SE 7


Other than download some Apache string utils, I don't think there is
anything better than just using a loop. Most of the examples here were
fairly in efficient: extra concatenation or recursion are going to be
less efficient, potentially *a lot* less efficient.

The only thing I'd add would be an explicit test to see if you need to
bother or not (which could be a micro-optimization), and maybe consider
CharSequence instead of just String.

   public CharSequence rTrim( CharSequence cs ) {
     if( cs == null ) return null;
     if( cs.length() == 0 || cs.charAt( cs.length()-1 ) != ' ' )
       return cs;
     int i = cs.length()-1;
     while( i >= 0 && cs.charAt( i ) == ' ' ) i--;
     return cs.substring( 0, i );
   }

Not compiled or tested.


You called for an elegant solution and explicitly excluded loops.
Elegant is a relative term and you did not state the need for an
efficient solution. I consider a short-and-simple solution elegant until
it has been proven too inefficient for the purpose of its application.

In all other circumstances this solution (apart from being incorrect)
reeks like premature optimization.

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