Nick Heiner Nick Heiner - 4 months ago 16
Java Question

Java: Pick a random value from an enum?

If I have an enum like this:

public enum Letter {
A,
B,
C,
//...
}


What is the best way to pick one randomly? It doesn't need to be production quality bulletproof, but a fairly even distribution would be nice.

I could do something like this

private Letter randomLetter() {
int pick = new Random().nextInt(Letter.values().length);
return Letter.values()[pick];
}


But is there a better way? I feel like this is something that's been solved before.

Answer

The only thing I would suggest is caching the result of values() because each call copies an array. Also, don't create a Random every time. Keep one. Other than that what you're doing is fine. So:

public enum Letter {
  A,
  B,
  C,
  //...

  private static final List<Letter> VALUES =
    Collections.unmodifiableList(Arrays.asList(values()));
  private static final int SIZE = VALUES.size();
  private static final Random RANDOM = new Random();

  public static Letter randomLetter()  {
    return VALUES.get(RANDOM.nextInt(SIZE));
  }
}
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