Can I assume that Java enumerations auto-increment by 1?

Question

Java states that the ordinal of the initial value is 0. Can I assume that when I create an enumeration like this :

public enum Direction {MONDAY, TUESDAY, WEDNESDAY, THURSDAY, ...}

That the ordinal of TUESDAY is always 1, that of WEDNESDAY always 2, ...?

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I'll be a bit more specific. I'm declaring an enumeration :

public enum Direction {UP,RIGHT,DOWN,LEFT}

Now there's a method to turn 90 degrees (clockwise). It's one line with ordinals :

direction = Direction.values()[direction.ordinal()+1 % Direction.values().length];

If I wouldn't use ordinals I would have to use switch statements or conditions :

switch (direction) {
    case LEFT:newdirection = Direction.UP;
    break;
  etc...
}

There are a couple advantages to using ordinals :

• shorter code
• faster code (negligeable)
• if a direction is added (for example DOWN_LEFT) the implementation doesn't necessarily have to change if you put the new direction at the right spot

What do you think?

Answer 1

Yes - see javadoc:

Returns the ordinal of this enumeration constant (its position in its enum declaration, where the initial constant is assigned an ordinal of zero).

Answer 2

Yes - but your code should not rely on it because then it will break when someone inserts Caturday.