Digital Analogue

Ok, geek time

I just read the niftiest new thing I've seen in a while. I've hated certain aspects of Java pretty much since it came out in the mid-90s, but for several years now we've known the feature list of Java 1.5, and it addressed my complaints, and threw in a few other nice things that I hadn't complained about, but appreciate the improvement.

So for maybe three years now, I've been raving about Java 1.5 despite not actually being able to write anything in it—it's been out quite a while now, but not on all platforms, and general adoption has been slow in some areas. Anyway, in helping a student decide how to implement a certain aspect of his project, I wanted to check out how Java 1.5 implemented the enumerated types I'd heard about.

They're so cool!

The basic enumerated type has been around for decades: in Pascal, for instance, you could say

type Month = (Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec);
var m: Month;
m := May;

So I figured Java's enums were out of this mould, probably more like Pascal than C but still just slightly fancy numbers. No, no, no. Java enums are quite a high-level construct, in fact; while you can treat them like Pascal enums, they can also carry data and behaviours just like any other object. Because in Java, an "enumerated type" is just a class whose instances are all known at compile time. So if you have a limited list of things, like notes on a scale or planets in a solar system or items in a pull-down menu, regardless of how complex those objects are, you get to use an enumerated type.

And a few things come for free when you define an enum, like values() and toString(), which along with the "for-each" loop (another grand new construct in Java 1.5) lets you write stuff like

  public enum Suit { SPADES, HEARTS, DIAMONDS, CLUBS }
  ...
  for (Suit s: Suit.values() ) {
    System.out.println (s);
  }

The Joys of Finnish:
"Kokko, Kokoon koko kokko." ("Kokko, gather together the whole bonfire.")
"Kokoko kokko?" ("The whole bonfire?")
"Koko kokko, Kokko." ("The whole bonfire, Kokko.") --Eric Dahlman