Re: Call by Result

From:

Nigel Wade <nmw-news@ion.le.ac.uk>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 10 Jun 2011 10:03:26 +0100

Message-ID:

<95e4uuF3cvU1@mid.individual.net>

On 10/06/11 08:33, Andreas Leitgeb wrote:

Gene Wirchenko <genew@ocis.net> wrote:

     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's three basic ways to do it:

1) Return null to indicate failure.

2) instead of the string, pass a mutable container of a string:

3) encode the String: e.g.: prepend a particular text to "success"-

Are 1) and 3) not precluded by the proviso "It is not acceptable to have
a special String value mean failure".

A fourth way would be to return a class/object containing both the
boolean and the String. To me, this would be the natural OO way of
returning more information than a primitive type.

And a 5th way could be to return the String and throw an Exception if it
did not work. Some purists may argue that failure to work is not
strictly an exception, but if it gets the job done...

--
Nigel Wade