In Java you can define abstract methods for an enum type to override it with a concrete method in a constant-specific class body (see Effective Java, 2nd Ed., page 152). When I try to do the same in Groovy I get a compilation error:
Can't have an abstract method in a non-abstract class. The class 'Day' must be declared abstract or the method 'java.lang.String getAction()' must be implemented.
This compilation error can be reproduced with this enum:
An enum in Groovy should provide the same behavior for enums as Java.