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Groups > comp.lang.java.programmer > #13253

Re: Keeping the split token in a Java regular expression

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On 03/27/2012 11:21 PM, Daniel Pitts wrote:
> On 3/27/12 2:01 PM, Robert Klemme wrote:
>> On 03/27/2012 03:46 AM, Arne Vajhøj wrote:
>>> On 3/26/2012 4:01 PM, Robert Klemme wrote:
>>>> On 03/26/2012 09:22 PM, Lew wrote:
>>
>>>>> Based on what you've shown it looks like you could split on the comma
>>>>> and trim the resulting strings.
>>>>
>>>> And one wouldn't even need a regular expression for that.
>>>> http://docs.oracle.com/javase/6/docs/api/java/util/StringTokenizer.html
>>>
>>> StringTokenizer is somewhat obsoleted by String split.
>>
>> I find regular expressions are quite a bit of overhead for splitting at
>> commas only. (Now we know that the OP has more demanding requirements so
>> regexp is probably the tool of choice.)
>>
>> Hmm... I don't like those methods in class String that much which use a
>> String with a regular expression which is then parsed on every
>> invocation of the method. That might be good for one off usage but for
>> everything else I prefer solutions which at least use a Pattern constant
>> to avoid parsing overhead per call.
> Premature optimization. Regex parsing inside an inner loop *migh* add
> unacceptable overhead, however that should be determined via profiling.

That's not the only reason, because:

>> Even if it wasn't for runtime
>> overhead of parsing I like to have the constant which can have it's own
>> JavaDoc explaining what's going on plus I can reuse it and quickly find
>> all places of usage etc.
> That's a better reason to factor it out.

I forgot to add another point: regular expressions tend to grow large 
which makes methods which contain such a regexp string constant harder 
to read.

And then of course there is another difference: with the Pattern in a 
static variable you'll notice earlier (at class load time) if the 
pattern is ill formatted as opposed to using ad hoc compilation which 
comes to haunt you later on every method invocation.

> My personal philosophy for this kind of thing:
> Correct first, easy second, fast third.

+1

Kind regards

	robert

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Keeping the split token in a Java regular expression laredotornado <laredotornado@zipmail.com> - 2012-03-26 11:54 -0700
  Re: Keeping the split token in a Java regular expression Lew <lewbloch@gmail.com> - 2012-03-26 12:22 -0700
    Re: Keeping the split token in a Java regular expression Robert Klemme <shortcutter@googlemail.com> - 2012-03-26 22:01 +0200
      Re: Keeping the split token in a Java regular expression Arne Vajhøj <arne@vajhoej.dk> - 2012-03-26 21:46 -0400
        Re: Keeping the split token in a Java regular expression Robert Klemme <shortcutter@googlemail.com> - 2012-03-27 23:01 +0200
          Re: Keeping the split token in a Java regular expression Arne Vajhøj <arne@vajhoej.dk> - 2012-03-27 17:18 -0400
          Re: Keeping the split token in a Java regular expression Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-27 14:21 -0700
            Re: Keeping the split token in a Java regular expression Robert Klemme <shortcutter@googlemail.com> - 2012-03-28 07:38 +0200
              Re: Keeping the split token in a Java regular expression Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-28 10:24 -0700
  Re: Keeping the split token in a Java regular expression markspace <-@.> - 2012-03-26 13:49 -0700
  Re: Keeping the split token in a Java regular expression laredotornado@gmail.com - 2012-03-26 14:21 -0700
    Re: Keeping the split token in a Java regular expression markspace <-@.> - 2012-03-26 15:02 -0700
    Re: Keeping the split token in a Java regular expression Knute Johnson <nospam@knutejohnson.com> - 2012-03-26 15:56 -0700
      Re: Keeping the split token in a Java regular expression markspace <-@.> - 2012-03-26 16:02 -0700
        Re: Keeping the split token in a Java regular expression Knute Johnson <nospam@knutejohnson.com> - 2012-03-26 17:33 -0700
          Re: Keeping the split token in a Java regular expression Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-27 01:17 +0000
            Re: Keeping the split token in a Java regular expression Martin Gregorie <martin@address-in-sig.invalid> - 2012-03-27 21:57 +0000
    Re: Keeping the split token in a Java regular expression Gene Wirchenko <genew@ocis.net> - 2012-03-26 18:26 -0700
      Re: Keeping the split token in a Java regular expression Lew <lewbloch@gmail.com> - 2012-03-26 19:07 -0700
        Re: Keeping the split token in a Java regular expression Knute Johnson <nospam@knutejohnson.com> - 2012-03-26 20:40 -0700
          Re: Keeping the split token in a Java regular expression Gene Wirchenko <genew@ocis.net> - 2012-03-27 09:10 -0700
            Re: Keeping the split token in a Java regular expression Lew <lewbloch@gmail.com> - 2012-03-27 11:09 -0700
              Re: Keeping the split token in a Java regular expression Gene Wirchenko <genew@ocis.net> - 2012-03-27 13:32 -0700
                Re: Keeping the split token in a Java regular expression Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-27 14:29 -0700
                Re: Keeping the split token in a Java regular expression Gene Wirchenko <genew@ocis.net> - 2012-03-27 16:22 -0700
                Re: Keeping the split token in a Java regular expression Gene Wirchenko <genew@ocis.net> - 2012-03-27 18:20 -0700
                Re: Keeping the split token in a Java regular expression Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-27 18:27 -0700
                Re: Keeping the split token in a Java regular expression Gene Wirchenko <genew@ocis.net> - 2012-03-27 21:31 -0700
                Re: Keeping the split token in a Java regular expression Robert Klemme <shortcutter@googlemail.com> - 2012-03-28 07:41 +0200
                Re: Keeping the split token in a Java regular expression Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-28 10:28 -0700
  Re: Keeping the split token in a Java regular expression Lew <lewbloch@gmail.com> - 2012-03-26 16:26 -0700
    Re: Keeping the split token in a Java regular expression Knute Johnson <nospam@knutejohnson.com> - 2012-03-26 17:36 -0700
    Re: Keeping the split token in a Java regular expression Robert Klemme <shortcutter@googlemail.com> - 2012-03-27 23:27 +0200
      Re: Keeping the split token in a Java regular expression Robert Klemme <shortcutter@googlemail.com> - 2012-03-28 07:28 +0200
  Re: Keeping the split token in a Java regular expression "John B. Matthews" <nospam@nospam.invalid> - 2012-03-26 20:49 -0400
  Re: Keeping the split token in a Java regular expression Arne Vajhøj <arne@vajhoej.dk> - 2012-03-26 21:58 -0400
    Re: Keeping the split token in a Java regular expression Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-26 21:14 -0700
      Re: Keeping the split token in a Java regular expression Arne Vajhøj <arne@vajhoej.dk> - 2012-03-27 17:21 -0400
        Re: Keeping the split token in a Java regular expression Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-27 15:20 -0700
          Re: Keeping the split token in a Java regular expression Arne Vajhøj <arne@vajhoej.dk> - 2012-03-27 18:48 -0400
            Re: Keeping the split token in a Java regular expression Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-27 17:07 -0700
          Re: Keeping the split token in a Java regular expression Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-03-27 21:49 -0300
            Re: Keeping the split token in a Java regular expression Arne Vajhøj <arne@vajhoej.dk> - 2012-03-27 20:56 -0400
              Re: Keeping the split token in a Java regular expression Arved Sandstrom <asandstrom3minus1@eastlink.ca> - 2012-03-27 22:01 -0300
                Re: Keeping the split token in a Java regular expression Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-27 18:27 -0700
  Re: Keeping the split token in a Java regular expression Jim Janney <jjanney@shell.xmission.com> - 2012-03-27 08:15 -0600
    Re: Keeping the split token in a Java regular expression laredotornado <laredotornado@zipmail.com> - 2012-03-27 07:58 -0700
      Re: Keeping the split token in a Java regular expression Jim Janney <jjanney@shell.xmission.com> - 2012-03-27 09:21 -0600
        Re: Keeping the split token in a Java regular expression Daniel Pitts <newsgroup.nospam@virtualinfinity.net> - 2012-03-27 09:43 -0700
          Re: Keeping the split token in a Java regular expression Robert Klemme <shortcutter@googlemail.com> - 2012-03-28 07:51 +0200

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