Re: ENUMs

From:

Lew <lew@nospam.lewscanon.com>

Newsgroups:

comp.lang.java.help

Date:

Sat, 17 Feb 2007 11:35:51 -0500

Message-ID:

<_NqdnXIFc950s0rYnZ2dnUVZ_hisnZ2d@comcast.com>

Jeff Higgins wrote:

class TestPromotion{ // this is only a test.

  public static void main(String args){
    System.out.println(Rank.PFC.promote());
  }

  public static enum Rank {
    PRIVATE,
    PFC,
    CORPORAL,
    SERGENT,
    CAPTAIN,
    MAJOR,
    LT_COLONEL,
    COLONEL,
    GENERAL,
    ADMIRAL;

    Rank promote(){
      Rank ret = null;
      Rank[] r = Rank.values();
      if(!this.equals(r[r.length-1])){
        for(int i=0; i<r.length; i++)
          if(this.equals(r[i])){
            ret = r[i+1];
            return ret;
        }
      }
      return ret;
    }
  };
}

John wrote:

Fantastic. Question...why does the promote method have to be in the
enum? I would rather have the promote method in the Soldier class. Is
there a way to do this?

You call it from the Soldier class. A Soldier doesn't know the rank system,
the rank system does. The Soldier relies on the rank system to know its own
promotion order. It then simply assigns to its internal instance variable the
value of the promoted Rank.

"Ours is not to wonder why, ours is but to do and die." - Alfred, Lord Tennyson.

Otherwise every class that uses Rank would have to implement its own idea of
Rank order, which would be stupid for most purposes and possibly mutually
contradictory, a risk factor for bugs.

You could possibly kludge a method in Soldier to do what Rank should do, but
it would be terrible design to do so.

- Lew