Item 31 - Use instance fields instead of ordinals
From Effective Java 2/e by Joshua Bloch
Never derive a value associated with an enum from its ordinal; store it in an instance field instead
// Abuse of ordinal to derive an associated value - DON'T DO THIS
public enum Ensemble {
SOLO, DUET, TRIO, QUARTET, QUINTET,
SEXTET, SEPTET, OCTET, NONET, DECTET;
public int numberOfMusicians() {
return ordinal() + 1;
}
}
public enum Ensemble {
SOLO(1), DUET(2), TRIO(3), QUARTET(4), QUINTET(5),
SEXTET(6), SEPTET(7), OCTET(8), DOUBLE_QUARTET(8),
NONET(9), DECTET(10), TRIPLE_QUARTET(12);
private final int numberOfMusicians;
Ensemble(int size) {
this.numberOfMusicians = size;
}
public int numberOfMusicians() {
return numberOfMusicians;
}
}
Enum specification has this to say about ordinal
Most programmers will have no use for this method. It is designed for use by general-purpose enum- based data structures such as EnumSet and EnumMap.
