Java Enum.valueOf() efficiency when value does not exist

Question

Which would you consider more efficient?

The use of \'WeekDay\' is just an example:

public enum WeekDay {
    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDA         


        

Answer 1

Store the valid strings in a HashSet, and decide whether a string is a valid day or not based on Set.contains(...).

The set can be a static final Set, and you can wrap in an unmodifiable for good measure:

private static final Map WEEKDAY_STRINGS;
static {
  HashSet set = new HashSet();
  for (WeekDay d : WeekDay.values()) {
    set.add(d.toString());
  }
  WEEKDAY_STRINGS = Collections.unmodifiableSet(set);
}