Case-insensitive matching of a string to a Java enum

Question

Java provides a valueOf() method for every Enum<T> object, so given an enum like

public enum Day {   Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday } 

one can do a lookup like

Day day = Day.valueOf("Monday"); 

If the string passed to valueOf() does not match (case sensitive) an existing Day value, an IllegalArgumentException is thrown.

To do a case-insensitive matching, one can write a custom method inside the Day enum, e.g.

public static Day lookup(String day) {   for (Day d : Day.values()) {     if (d.name().equalsIgnoreCase(day)) {       return type;     }   }   return null; } 

Is there any generic way, without using caching of values or any other extra objects, to write a static lookup() method like the above only once (i.e., not for every enum), given that the values() method is implicitly added to the Enum<E> class at compile time?

The signature of such a "generic" lookup() method would be similar to the Enum.valueOf() method, i.e.:

public static <T extends Enum<T>> T lookup(Class<T> enumType, String name); 

and it would implement exactly the functionality of the Day.lookup() method for any enum, without the need to re-write the same method for each enum.

Answer 1

I found getting the special blend of generics a little tricky, but this works.

public static <T extends Enum<?>> T searchEnum(Class<T> enumeration,         String search) {     for (T each : enumeration.getEnumConstants()) {         if (each.name().compareToIgnoreCase(search) == 0) {             return each;         }     }     return null; } 

Example

public enum Horse {     THREE_LEG_JOE, GLUE_FACTORY };  public static void main(String[] args) {     System.out.println(searchEnum(Horse.class, "Three_Leg_Joe"));     System.out.println(searchEnum(Day.class, "ThUrSdAy")); }