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From: =?ISO-8859-1?Q?S=E9bastien_Lorber?= <lorber.sebastien@gmail.com>
Date: Thu, 18 Aug 2011 16:01:30 +0200
Message-ID: 
 <CADvQ-boXM9oacoO02avAF51jV1pv8vbqzjcOFDDFe1_vtSrNvQ@mail.gmail.com>
Subject: Re: [collections] Iterate over sublists of an original list
To: Commons Developers List <dev@commons.apache.org>
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That's true.

The grouped() method in scala do exactly that.

I agree, these functions are quite useful that's why i sent a mail: to see
if we can integrate them in apache libs


2011/8/18 Matthew Pocock <turingatemyhamster@gmail.com>

> The scala collections library has the grouped() method. From the scaladoc=
:
>
> defgrouped (size: Int <
> http://www.scala-lang.org/api/current/scala/Int.html>
> ): Iterator<
> http://www.scala-lang.org/api/current/scala/collection/Iterator.html>
> [List<
> http://www.scala-lang.org/api/current/scala/collection/immutable/List.htm=
l
> >
> [A]]
>
> Partitions elements in fixed size lists.
> size
>
> the number of elements per group
> returns
>
> An iterator producing lists of size size, except the last will be truncat=
ed
> if the elements don't divide evenly.
>
> I'm not suggesting you should jump to scala to use its collections librar=
y,
> or even use scala-library.jar from your Java app, but I do find this meth=
od
> together with groupBy() one of the more useful bits of functionality. Pit=
y
> something like it isn't supported by other 3rd party collections for Java=
.
>
> Matthew
>
> On 18 August 2011 13:48, S=E9bastien Lorber <lorber.sebastien@gmail.com
> >wrote:
>
> > Hello
> >
> > Actually if you look at my implementation, i use that List.sublist()
> > method.
> >
> > It's a little pain to use it to split because you must always take care
> of
> > an out of bound...
> > IMHO, people do not really like to play with array/list indexes... If
> they
> > just want to split a big list of a couple of small sublists,
> > they probably do not like to have to deal with calculating the good ind=
ex
> > positions, they just want the list to be splitted :)
> >
> > I've looked at some guava classes but wasn't able to find anything to d=
o
> > this: a convenient way to split a list
> >
> >
> >
> > 2011/8/18 David Karlsen <davidkarlsen@gmail.com>
> >
> > > Guava also has a lot of handy classes for working on collections.
> > >
> > > 2011/8/18 Simone Tripodi <simonetripodi@apache.org>
> > >
> > > > Salut S=E9bastien,
> > > > wouldn't the List#subList(int, int)[1] method be helpful for your
> > > purposes?
> > > > HTH,
> > > > Simo
> > > >
> > > > [1]
> > > >
> > >
> >
> http://download.oracle.com/javase/1.5.0/docs/api/java/util/List.html#subL=
ist(int
> > > > ,
> > > > int)
> > > >
> > > >
> > > > http://people.apache.org/~simonetripodi/
> > > > http://www.99soft.org/
> > > >
> > > >
> > > >
> > > > On Thu, Aug 18, 2011 at 2:26 PM, S=E9bastien Lorber
> > > > <lorber.sebastien@gmail.com> wrote:
> > > > > Hello,
> > > > >
> > > > >
> > > > > It's not the first time i have to split a big list of hibernate
> > > entities
> > > > > ID's to sublists of 100 items for exemple so that i could load al=
l
> > > these
> > > > > entities 100 in a single request (with a "where id in (<id
> sublist>")
> > > > >
> > > > > Thus I want to iterate easily on sublists of a list, with the
> > > possibility
> > > > to
> > > > > give the sublist a size...
> > > > > I though i would find the tool in apache collections but i didn't
> > find
> > > > it.
> > > > > Perhaps i've missed the class...
> > > > >
> > > > >
> > > > >
> > > > > If there's no tool to do that yet, i think it would be great to
> make
> > > one
> > > > in
> > > > > apache collections.
> > > > >
> > > > > The kinda simple implementation i use at work is the following:
> > > > > http://pastebin.com/CRitkWTG
> > > > >
> > > > >
> > > > > And you use it like that:
> > > > >
> > > > >        // We load vehicles 100 by 100
> > > > >         for ( List<String> idSublist : new
> > > > > SublistIterable<String>(allIds,100) ) {
> > > > >            List<Vehicle> vehiclesSublist =3D
> > > > vehicleDAO.findByIds(idSublist);
> > > > >            // blablabla
> > > > >        }
> > > > >
> > > >
> > > > -------------------------------------------------------------------=
--
> > > > To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
> > > > For additional commands, e-mail: dev-help@commons.apache.org
> > > >
> > > >
> > >
> > >
> > > --
> > > --
> > > David J. M. Karlsen - http://www.linkedin.com/in/davidkarlsen
> > >
> >
>
>
>
> --
> Dr Matthew Pocock
> Visitor, School of Computing Science, Newcastle University
> mailto: turingatemyhamster@gmail.com
> gchat: turingatemyhamster@gmail.com
> msn: matthew_pocock@yahoo.co.uk
> irc.freenode.net: drdozer
> tel: (0191) 2566550
> mob: +447535664143
>

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