Is it good practice to use ordinal of enum?

Question

I have an enum:

public enum Persons {

    CHILD,
    PARENT,
    GRANDPARENT;

}

Is there any problem with using ordinal() method to check "hierarchy" between enum members? I mean - is there any disadvantages when using it excluding verbosity, when somebody can change accidentally order in future.

Or is it better to do something like that:

public enum Persons {

    CHILD(0),
    PARENT(1),
    GRANDPARENT(2);

    private Integer hierarchy;

    private Persons(final Integer hierarchy) {
        this.hierarchy = hierarchy;
    }

    public Integer getHierarchy() {
        return hierarchy;
    }

}

Answer 1

TLDR: No, you should not!

If you refer to the javadoc for ordinal method in Enum.java:

Most programmers will have no use for this method. It is designed for use by sophisticated enum-based data structures, such as java.util.EnumSet and java.util.EnumMap.

Firstly - read the manual (javadoc in this case).

Secondly - don't write brittle code. The enum values may change in future and your second code example is much more clear and maintainable.

You definitely don't want to create problems for the future if a new enum value is (say) inserted between PARENT and GRANDPARENT.

Answer 2

As suggested by Joshua Bloch in Effective Java, it's not a good idea to derive a value associated with an enum from its ordinal, because changes to the ordering of the enum values might break the logic you encoded.

The second approach you mention follows exactly what the author proposes, which is storing the value in a separate field.

I would say that the alternative you suggested is definitely better because it is more extendable and maintainable, as you are decoupling the ordering of the enum values and the notion of hierarchy.