Re: Nested enums

From:
"ricky.clarkson@gmail.com" <ricky.clarkson@gmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
10 Sep 2006 09:20:21 -0700
Message-ID:
<1157905221.484484.112990@p79g2000cwp.googlegroups.com>
Definitely.

I've written an IP stack or two in Java, and it didn't help that on the
second one I was just starting to learn Java 1.5's features - it took
quite some messing around before I got it right (assuming I actually
did get it right!).

The IP stack is in IPSim ( http://www.ipsim.com ), FYI.

unomystEz wrote:

Hey ricky,

   Sorry for the delay in the reply.. good to know you are here as
well.

After reading your reply it does make sense to me to start from an
interface perspective and see where it ends up rather than trying to
leverage enums (I've been on an enum kick lately =))

Dealing with protocol suites can be quite messy, especially when you
try to design it cleanly, use it safely and synchronize it against its'
documentation.

regards

ricky.clarkson@gmail.com wrote:

I recognise that name..

Try not to design in terms of enums, but in terms of interfaces. If
the implementation ends up looking like an enum, then sure, for
clarity, make it an enum.

In this example, I would have something like:

interface MajorCommand
{
        Iterable<SubCommand> possibleValues();
}

interface SubCommand
{
}

enum Commands
{
        LOGON
        {
                public Iterable<SubCommand> possibleValues()
                {
                        return Collections.emptySet();
                }
        },
        QUIT
        {
                public Iterable<SubCommand> possibleValues()
                {
                        SubCommand[]
subCommands=QuitSubCommands.values();
                        return Arrays.asList(subCommands);
                }
        },
        LIGHT
        {
                public Iterable<SubCommand> possibleValues()
                {
                        SubCommand[]
subCommands=LightSubCommands.values();
                        return Arrays.asList(subCommands);
                }
        }
}

enum QuitSubCommands
{
        IMMEDIATELY,
        DELAY
}

enum LightSubCommands
{
        TURN_ON,
        TURN_OFF
}

unomystEz wrote:

I have a protocol structure that makes use of subcommands and I was
wondering if it's possible to do something like the following:

public enum MajorCommand {

    LOGON { public enum SubCommand { }; }

    QUIT { public enum SubCommand { IMMEDIATELY, DELAY }; }

    LIGHT { public enum SubCommand { TURN_ON, TURN OFF}; }

   public abstract enum SubCommand;

}

It would help a lot with the organization of the various combinations
possible.

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