Breaking up a large Java enum

Question

What is the recommended practice for taking a Java enum that has say 1300 values and putting it into organized groups? I know you can't just extends the enum group, so are there other good alternatives?

Answer 1

I would use an interface which these instances all share, then you can use any number of enums or load them from another data source such as a file or database.

Answer 2

1300 values? Good god, who thought that was a good idea? Did it not occur to someone after 100 that it was getting too big?

There's no good way around it that I can see. Get a shovel and start combining them into more cohesive sub-enums.

Here's a question: How are they used? If they are part of your application configuration, I'd recommend moving them to a database rather than keeping them in code. They'll be more flexible that way.

Answer 3

you can break them up like:

import java.util.*;
interface Children {
    Set<Enum<?>> children();
}
enum Dog implements Children {
    myDog,yourDog;
    Dog() {
        this(null);
    }
    Dog(Set<Enum<?>> children) {
        this.children=children;
    }
    @Override public Set<Enum<?>> children() {
        return children!=null?Collections.unmodifiableSet(children):null;
    }
    Set<Enum<?>> children;
}
enum Animal implements Children {
    cat,dog(EnumSet.allOf(Dog.class));
    Animal() {
        this(null);
    }
    Animal(Set children) {
        this.children=children;
    }
    @Override public Set<Enum<?>> children() {
        return children!=null?Collections.unmodifiableSet(children):null;
    }
    Set<Enum<?>> children;
}
enum Thing implements Children {
    animal(EnumSet.allOf(Animal.class)),vegetable,mineral;
    Thing() {
        this(null);
    }
    Thing(Set children) {
        this.children=children;
    }
    @Override public Set<Enum<?>> children() {
        return children!=null?Collections.unmodifiableSet(children):null;
    }
    Set<Enum<?>> children;
}
public class So8671088 {
    static void visit(Class<?> clazz) {
        Object[] enumConstants = clazz.getEnumConstants();
        if (enumConstants[0] instanceof Children) for (Object o : enumConstants)
            visit((Children) o, clazz.getName());
    }
    static void visit(Children children, String prefix) {
        if (children instanceof Enum) {
            System.out.println(prefix + ' ' + children);
            if (children.children() != null) for (Object o : children.children())
                visit((Children) o, prefix + ' ' + children);
        } else
            System.out.println("other " + children.getClass());
    }
    public static void main(String[] args) {
        visit(Thing.animal," ");
        visit(Thing.class);
    }
}