Re: Enum Idiom Question

From:

=?ISO-8859-1?Q?Arne_Vajh=F8j?= <arne@vajhoej.dk>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 28 May 2010 20:08:20 -0400

Message-ID:

<4c005ae9$0$281$14726298@news.sunsite.dk>

On 28-05-2010 19:02, Rhino wrote:

I'm trying something Eric Sosman suggested on another thread but I have
doubts about one of the idioms so I thought I'd check here and see if there
was a better way.

A method name pad() returns a special class called PadResult. PadResult is
defined as follows:

public class PadResult {

CompletionStatus status;

String result;

The accessability level of package does not seem right.

public enum CompletionStatus {

/** Constant for ERROR. */

ERROR,

/** Constant for NO_ERROR */

NO_ERROR;

}

The method is then invoked as follows:

PadResult padResult = PadUtils.pad("Footsy", ' ', 't', 3); //Pad Footsy with
trailing blanks and make the final result 3 characters long

Since this should fail because the requested final length would truncate the
input string, pad() will return CompletionStatus.ERROR and an error message
via PadResult.

I'm checking the value of the CompletionStatus as follows:

if (padResult.getStatus()==CompletionStatus.ERROR) {

System.out.println(padResult.getResult());

}

It's the if statement that concerns me here. This code works fine (I can
test for CompletionStatus.NO_ERROR by simply changlng the right side of the
if) but it doesn't look right. It reminds me of mistakes I made when I was
new to Java comparing Strings to each other via the == operator to see if
they had the same VALUE but discovering that == doesn't determine equality
of value.

Is there a better way to do this if statement? If so, what is it?

I would compare with CompletionStatus.NO_ERROR, because it is
a lot more likely that you will have more than one error status
than more than one no error status.

I would seriously consider instead of the enum to have a boolean
plus a String, because true/false and a textual explanation is
really what you need.

If an error is something that warrants an exception then
you could simply the code by using an exception.

Some error situations could even warrant an uncheck
exception (deriving from RuntimException).

Arne