Retrieving an enum using 'valueOf' throws RuntimeException - What to use instead?

You can use the getEnum Method vom the apache EnumUtils library. It returns the enum or null if not found.

EnumUtils.getEnum(Animal.class, "CAT");

How about creating a HashMap<String, Mammal>? You only need to do it once...

public class Foo {

  private static final Map<String, Mammal> NAME_TO_MAMMAL_MAP;

  static {
    NAME_TO_MAMMAL_MAP = new HashMap<String, Mammal>();
    for (Human human : EnumSet.allOf(Human.class)) {
      NAME_TO_MAMMAL_MAP.put(human.name(), human);
    }
    for (Animal animal : EnumSet.allOf(Animal.class)) {
      NAME_TO_MAMMAL_MAP.put(animal.name(), animal);
    }
  }

  public static Mammal bar(final String arg) {
    return NAME_TO_MAMMAL_MAP.get(arg);
  }
}

Notes:

• This will return null if the name doesn't exist
• This won't detect a name collision
• You may want to use an immutable map of some description (e.g. via Guava)
• You may wish to write a utility method to create an immutable name-to-value map for a general enum, then just merge the maps :)