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From: Eric Sosman <esosman@comcast-dot-net.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: Good pattern for realizing the out-param capability in Java?
Date: Wed, 14 Sep 2016 17:25:01 -0400
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On 9/14/2016 3:54 PM, Eric Douglas wrote:
> On Wednesday, September 14, 2016 at 12:17:37 PM UTC-4, sande...@yahoo.com wrote:
>> I want to solicit the opinion of the Java experts about realizing the out-param capability in Java.  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
>>         …
>>     }
>>     …
>> }
>
> Methods don't normally need to pass out more than one value, so when they do I either create a custom object or pass out an array.  What advantage would you get from creating a generic custom class to pass out 2 values?

     I disagree with the premise: It is fairly common for a computation
to generate more than one result.  On the other hand, I agree with the
approach: It is (I feel) better to return the multiple results in a
single instance of a "holder" class.  java.awt.Shape's getBounds()
method returns its *four* outputs in a java.awt.Rectangle instance,
and there are many similar examples among the standard classes.

     Occasionally, though, the "out-param" simply cannot be avoided.
The various sort() methods of java.util.Arrays, for example, would be
a good deal less attractive if they left their argument arrays
unmodified and instead returned brand-new arrays as method results ...

-- 
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