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From: Eric Sosman <esosman@ieee-dot-org.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: Call by Result
Date: Fri, 10 Jun 2011 07:50:55 -0400
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On 6/10/2011 2:03 AM, Gene Wirchenko wrote:
> Dear Java'ers:
>
>       I wish to call by result with a method.  Is it possible?  If not,
> can it be easily simulated in an unnasty way?
>
>       I am writing a simple preprocessor.  I have a few spots where a
> string needs to be parsed.  I want to call something like this:
>            String ReturnString="";
>            boolean DidItWork=GetString(ReturnString);
>            if (!DidItWork)
>               // too bad
> It is not acceptable to have a special String value mean failure.  I
> want the method to be able to return any potential string.

     There are lots of ways to do what I think you want (the phrase
"call by result" is new to me).  One is

	class ResultHolder {
	    String returnString;
	    // ... other stuff, if desired
	};

	ResultHolder result = new ResultHolder();
	result.returnString = "";  // if desired
	boolean didItWork = getString(result);
	if (didItWork)
	    System.out.println("Result is " + result.returnString);
	else
	    System.err.println("Woe is me!");

     The same thing, really, in a quick-and-dirty form:

	String[] result = new String[1];
	boolean didItWork = getString(result);
	if (didItWork)
	    System.out.println("Result is " + result[0]);
	else
	    System.err.println("Woe is me!");

     Still another variation is to put the String and the boolean
in the same holder class (I'd be tempted to rename the boolean to
something like isValid).

     Of course, there's a completely different approach:

	try {
	    String result = getString();
	    System.out.println("Result is " + result);
	} catch (ItsNoGoodException ex) {
	    System.err.println("Woe is me!");
	}

... and I'm sure there are possibilities beyond these.

-- 
Eric Sosman
esosman@ieee-dot-org.invalid