Best practice to look up Java Enum

Question

We have a REST API where clients can supply parameters representing values defined on the server in Java Enums.

So we can provide a descriptive error, we add this lookup method to each Enum. Seems like we're just copying code (bad). Is there a better practice?

public enum MyEnum {     A, B, C, D;      public static MyEnum lookup(String id) {         try {             return MyEnum.valueOf(id);         } catch (IllegalArgumentException e) {             throw new RuntimeException("Invalid value for my enum blah blah: " + id);         }     } } 

Update: The default error message provided by valueOf(..) would be No enum const class a.b.c.MyEnum.BadValue. I would like to provide a more descriptive error from the API.

Answer 1

Probably you can implement generic static lookup method.

Like so

public class LookupUtil {    public static <E extends Enum<E>> E lookup(Class<E> e, String id) {          try {                    E result = Enum.valueOf(e, id);       } catch (IllegalArgumentException e) {          // log error or something here           throw new RuntimeException(            "Invalid value for enum " + e.getSimpleName() + ": " + id);       }        return result;    } } 

Then you can

public enum MyEnum {    static public MyEnum lookup(String id) {        return LookupUtil.lookup(MyEnum.class, id);    } } 

or call explicitly utility class lookup method.