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Re: Substring changes (JDK 1.7)

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Chris Uppal schrieb:
>> For example I trapped myself doing things like:
>> >
>> >     int k = path.lastIndexOf('/');
>> >     while (k!=-1) {
>> >         String name = path.substring(k+1);
>> >         /* do something with name */
>> >         path = path.substring(0,k);
>> >         k = path.lastIndexOf('/');
>> >     }
>> >
> And what's wrong with that ?  Seems a sensible approach to me.
>
> If you mean that it's suddenly/significantly/  slower, then I don't believe
> you.  (Though I freely admit that there will be a tiny few cases where it
> /does/  matter -- in which cases I will be wrong.)
>
>      -- chris
>
>

With the sharing semantics, its complexity is O(n+m), where
n is the length of the string and m is the number of
backslashes. The m counts for the number of creation of
shared String shells.

Without the sharing semantics, when substring copies, its
complexity is O(n^2), assuming m is not too small. In each
of the m interation you do not anymore create a String shell,
but instead in the following statement

          path = path.substring(0,k);

you do copy a fair amount of path. JDK 1.7 Update 10 has not
anymore the sharing semantics. So when my m are not too small,
its probably a good idea to rewrite the code.

Bye

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Thread

Substring changes (JDK 1.7) Jan Burse <janburse@fastmail.fm> - 2013-01-10 14:38 +0100
  Re: Substring changes (JDK 1.7) markspace <markspace@nospam.nospam> - 2013-01-10 08:15 -0800
    Re: Substring changes (JDK 1.7) Joshua Cranmer <Pidgeot18@verizon.invalid> - 2013-01-10 10:48 -0600
      Re: Substring changes (JDK 1.7) markspace <markspace@nospam.nospam> - 2013-01-10 09:22 -0800
        Re: Substring changes (JDK 1.7) Lars Enderin <lars.enderin@telia.com> - 2013-01-10 19:35 +0100
  Re: Substring changes (JDK 1.7) Jan Burse <janburse@fastmail.fm> - 2013-01-10 20:08 +0100
    Re: Substring changes (JDK 1.7) Jan Burse <janburse@fastmail.fm> - 2013-01-10 20:12 +0100
  Re: Substring changes (JDK 1.7) Roedy Green <see_website@mindprod.com.invalid> - 2013-01-10 12:22 -0800
    Re: Substring changes (JDK 1.7) Robert Klemme <shortcutter@googlemail.com> - 2013-01-10 22:58 +0100
      Re: Substring changes (JDK 1.7) Roedy Green <see_website@mindprod.com.invalid> - 2013-01-10 15:20 -0800
      Re: Substring changes (JDK 1.7) Robert Klemme <shortcutter@googlemail.com> - 2013-01-11 07:29 +0100
        Re: Substring changes (JDK 1.7) Roedy Green <see_website@mindprod.com.invalid> - 2013-01-10 23:19 -0800
          Re: Substring changes (JDK 1.7) Robert Klemme <shortcutter@googlemail.com> - 2013-01-12 17:50 +0100
            Re: Substring changes (JDK 1.7) markspace <markspace@nospam.nospam> - 2013-01-12 09:59 -0800
              Re: Substring changes (JDK 1.7) Jan Burse <janburse@fastmail.fm> - 2013-01-12 19:14 +0100
                Re: Substring changes (JDK 1.7) markspace <markspace@nospam.nospam> - 2013-01-12 10:36 -0800
                Re: Substring changes (JDK 1.7) Jan Burse <janburse@fastmail.fm> - 2013-01-13 12:09 +0100
    Re: Substring changes (JDK 1.7) Jan Burse <janburse@fastmail.fm> - 2013-01-11 09:23 +0100
      Re: Substring changes (JDK 1.7) "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2013-01-11 08:29 +0000
        Re: Substring changes (JDK 1.7) Jan Burse <janburse@fastmail.fm> - 2013-01-11 10:56 +0100
          Re: Substring changes (JDK 1.7) Jan Burse <janburse@fastmail.fm> - 2013-01-11 14:30 +0100

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