EnumMap or HashMap if lookup key is a String

Question

I'm trying to weigh the pros and cons of using an EnumMap over a HashMap. Since, I will always be looking up using a String, it seems that a HashMap with a String key would be the right choice. However, an EnumMap seems like better design because it conveys my intent to restrict keys to a specific enumeration. Thoughts?

Here is a make-believe example, showing how I will be using the Map:

enum AnimalType { CAT, DOG } interface Animal {} class Cat implements Animal {} class Dog implements Animal {}  public class AnimalFactory {      private static final Map<AnimalType, Animal> enumMap              = new EnumMap<AnimalType, Animal>(AnimalType.class);     // versus     private static final Map<String, Animal> stringMap              = new HashMap<String, Animal>();      static {         enumMap.put(AnimalType.CAT, new Cat());         enumMap.put(AnimalType.DOG, new Dog());         stringMap.put("CAT", new Cat());         stringMap.put("DOG", new Dog());     }     public static Animal create(String type) {         Animal result = enumMap.get(AnimalType.valueOf(type));         Animal result2 = stringMap.get(type);         return result;     } } 

Assume that the AnimalType enum and map will ONLY be used by the AnimalFactory to create animals and nowhere else.

Which Map should I use?

Answer 1

If all valid keys can be enumerated, I would use that as it ensures you are always working with a valid value.

It can also avoid confusion as String can be used for lots of things and is easy to turn an "Animal" string into a string used for something else. As enum types are not interchangable with other types in general (unless you use a common interface), there is less chance of error in coding.