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From: Robert Klemme <shortcutter@googlemail.com>
Newsgroups: comp.lang.java.programmer
Subject: Re: Good pattern for realizing the out-param capability in Java?
Date: Wed, 14 Sep 2016 18:43:24 +0200
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On 14.09.2016 18:17, sandeep6699@yahoo.com wrote:
> I want to solicit the opinion of the Java experts about realizing
> the  out-param capability in Java.

It's been quite a while since I have seen this asked but apparently some =

topics do not die.

> Suppose there is a method in a class where
> I would like to realize the following:
>
> class MyClass {
>     int myMethod(int inIntParam, int outIntParam, double outDoubleParam=
) {
>         // Accepts inIntParam as input
>         // Updates outIntParam and outDoubleParam
>         // Returns an int
>         =E2=80=A6
>     }
>     =E2=80=A6
> }
>
> Since primitive types are passed by values, and primitive type
> wrapper  classes are immutable, I am thinking of having outIntParam and=

> outDoubleParam as instance variables in the class, which get set prior
> to calling myMethod. Then myMethod can make do with only one parameter =
i.e.

This is a bad idea.  It will break under multithreaded usage.  Also,=20
design wise this state does not belong into the instance.  From the=20
instance's point of view this is purely transitional state which you now =

bind into the instance for ever.

> class MyClass {
>     protected int outIntParam;
>     protected double outDoubleParam;
>
>     int getOutIntParam() {
>         return outIntParam;
>     }
>
>     double getOutDoubleParam() {
>         return outDoubleParam;
>     }
>     //
>     // No Settors for these instance variables
>     // =E2=80=A6
>
>     int myMethod(int inIntParam) {
>         // Accepts inIntParam as input
>      // Updates instance variables in outIntParam and outDoubleParam
>     // Returns an int
>     =E2=80=A6
>     }
>     =E2=80=A6
> }
>
> Kindly suggest if there is a preferred way to realize the same.

Your example is pretty generic and does not say much about the real use=20
case.  In absence of more knowledge my advice is: create a class that=20
contains the necessary state and return an instance of that or receive=20
an instance of that class as parameter and manipulate it in the method - =

whichever is more appropriate for your use case.

Kind regards

	robert

--=20
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/