Groovy and enum demo. Groovy 1.8.9 doesn't suport enum's abstract method, but static initializer and metaClass makes nealy likely enable it. This is a work arround for http://jira.codehaus.org/browse/GROOVY-4641

groovy_enum_metaClass_demo1.groovy

// tested on Groovy 1.8.9.

enum GreetEnum {
    MORNING("Good Morning"),
    AFTERNOON("Good Afternoon"),
    EVENING("Good Evening");
    static {
        MORNING.metaClass.greeting = { String you ->
            return delegate.emphasize() + " " + you + ", I'm sleeping..."
        }
        AFTERNOON.metaClass.greeting = { String you ->
            return delegate.greet + " " + you + ", let's coffee break!"
        }
    }

    String greet

    GreetEnum(String _greet) {
        this.greet = _greet
    }

    String greeting(String you) {
        throw new UnsupportedOperationException()
    }

    String emphasize() {
        return this.greet + "!!"
    }
}

assert GreetEnum.MORNING.greeting("abc") == "Good Morning!! abc, I'm sleeping..."
assert GreetEnum.AFTERNOON.greeting("abc") == "Good Afternoon abc, let's coffee break!"
//Caught: java.lang.UnsupportedOperationException
//assert GreetEnum.EVENING.greeting("abc") == "Good Evening abc"