Groups > comp.lang.java.programmer > #22045

Re: refactoring problem

From	Martin Gregorie <martin@address-in-sig.invalid>
Newsgroups	comp.lang.java.programmer
Subject	Re: refactoring problem
Date	2013-02-03 16:23 +0000
Organization	UK Free Software Network
Message-ID	<kem2t6$jah$1@localhost.localdomain> (permalink)
References	<7fssg8dakvofmv6pk3sfvp5jmaku55vgmm@4ax.com>

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On Sun, 03 Feb 2013 06:30:40 -0800, Roedy Green wrote:

> Consider the following refactoring problem.
> 
> There is a hunk of almost identical code that appears multiple times.
> It sets up 6 local variables.
> 
> I would like to encapsulate it.
> 
>
> I could create a separate class just to hold the values.  This is
> tedious, but it may be the only way.
>
...which you can return from a method. I keep wondering whether I should 
use this approach but so far haven't used it.

> I think, why can methods have multiple inputs, but only one output? I
> have been thinking that for about 50 years, and it ,seems unlikely to
> change soon.
> 
Formally true, but not necessarily so in practice. You can return a class 
instance containing as many variables as you need to return.

You can also pass the constructor a reference to a mutable object which 
contains the variables you want to change. I use this quite a lot: its 
particularly useful for letting logically separate sets of methods access 
and manipulate a collection: each set of methods forms a class that's 
handed a reference to the collection.

Example: I've just finished dealing with a way of handling a collection 
of geographical points: Each point forms a Waypoint that contains 
coordinates and descriptive attributes together with the methods needed 
to access its (immutable) attributes. The collection forms a WaypointList 
class that holds a set of Waypoints as an ArrayList plus two TreeMaps 
that give keyed access to Waypoints and methods needed to add, remove and 
retrieve individual Waypoints. There is a requirement to read a waypoint 
file into the WaypointList and to write it out to a file: there are 
currently five externally defined waypoint file formats I need to deal 
with so there is a set of classes, one per file format, that each 
implement a load() and a save() method. 

In addition there will be three programs that carry out more complex 
operations on one or more WaypointLists: only one of these has been 
written so far.

-- 
martin@   | Martin Gregorie
gregorie. | Essex, UK
org       |

Thread

refactoring problem Roedy Green <see_website@mindprod.com.invalid> - 2013-02-03 06:30 -0800
  Re: refactoring problem Martin Gregorie <martin@address-in-sig.invalid> - 2013-02-03 16:23 +0000
  Re: refactoring problem Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-02-03 12:27 -0400
    Re: refactoring problem Roedy Green <see_website@mindprod.com.invalid> - 2013-02-03 12:35 -0800
      Re: refactoring problem Arne Vajhøj <arne@vajhoej.dk> - 2013-02-03 15:37 -0500
    Re: refactoring problem Leif Roar Moldskred <leifm@dimnakorr.com> - 2013-02-03 15:21 -0600
      Re: refactoring problem Arved Sandstrom <asandstrom2@eastlink.ca> - 2013-02-03 17:38 -0400
      Re: refactoring problem Arne Vajhøj <arne@vajhoej.dk> - 2013-02-03 16:46 -0500
    Re: refactoring problem Lew <lewbloch@gmail.com> - 2013-02-03 14:36 -0800
  Re: refactoring problem Arne Vajhøj <arne@vajhoej.dk> - 2013-02-03 11:34 -0500
  Re: refactoring problem Joshua Cranmer <Pidgeot18@verizon.invalid> - 2013-02-03 11:54 -0600
    Re: refactoring problem Arne Vajhøj <arne@vajhoej.dk> - 2013-02-03 13:13 -0500
      Re: refactoring problem Knute Johnson <nospam@knutejohnson.com> - 2013-02-03 10:20 -0800
        Re: refactoring problem Arne Vajhøj <arne@vajhoej.dk> - 2013-02-03 13:32 -0500
          Re: refactoring problem Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-02-03 10:50 -0800
            Re: refactoring problem Robert Klemme <shortcutter@googlemail.com> - 2013-02-03 21:38 +0100
            Re: refactoring problem "Chris Uppal" <chris.uppal@metagnostic.REMOVE-THIS.org> - 2013-02-04 08:11 +0000
              Re: refactoring problem Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2013-02-04 03:56 -0800
      Re: refactoring problem Silvio <silvio@internet.com> - 2013-02-04 13:21 +0100
        Re: refactoring problem Lew <lewbloch@gmail.com> - 2013-02-04 12:35 -0800
          Re: refactoring problem Silvio <silvio@internet.com> - 2013-02-04 22:15 +0100
            Re: refactoring problem Lew <lewbloch@gmail.com> - 2013-02-04 13:49 -0800
              Re: refactoring problem Silvio <silvio@internet.com> - 2013-02-04 23:51 +0100
            Re: refactoring problem Lew <lewbloch@gmail.com> - 2013-02-04 13:53 -0800
              Re: refactoring problem Silvio <silvio@internet.com> - 2013-02-04 23:48 +0100
                Re: refactoring problem Lew <lewbloch@gmail.com> - 2013-02-04 17:08 -0800
                Re: refactoring problem Silvio <silvio@internet.com> - 2013-02-05 10:07 +0100
                Re: refactoring problem Lew <lewbloch@gmail.com> - 2013-02-05 13:13 -0800
                Re: refactoring problem Jim Gibson <jimsgibson@gmail.com> - 2013-02-05 13:20 -0800
                Re: refactoring problem Lew <lewbloch@gmail.com> - 2013-02-05 13:31 -0800
                Re: refactoring problem Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 21:42 -0500
            Re: refactoring problem Arne Vajhøj <arne@vajhoej.dk> - 2013-02-04 18:33 -0500
          Re: refactoring problem Arne Vajhøj <arne@vajhoej.dk> - 2013-02-04 18:32 -0500
            Re: refactoring problem Martin Gregorie <martin@address-in-sig.invalid> - 2013-02-05 01:50 +0000
          Re: refactoring problem Joshua Cranmer <Pidgeot18@verizon.invalid> - 2013-02-05 10:04 -0600
            Re: refactoring problem Gene Wirchenko <genew@telus.net> - 2013-02-05 10:38 -0800
              Re: refactoring problem Joshua Cranmer <Pidgeot18@verizon.invalid> - 2013-02-05 13:53 -0600
            Re: refactoring problem Arne Vajhøj <arne@vajhoej.dk> - 2013-02-05 21:43 -0500
              Re: refactoring problem markspace <markspace@nospam.nospam> - 2013-02-05 19:15 -0800
                Re: refactoring problem Arne Vajhøj <arne@vajhoej.dk> - 2013-02-08 23:58 -0500
  Re: refactoring problem Joerg Meier <joergmmeier@arcor.de> - 2013-02-05 11:09 +0100

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