为什么Groovy Enums无法访问类变量？

Question

Could not find any documentation that explains why class variables are not accessible from within enums. Consider this example:

package groovy;

public class Universe {

    static String test = "test";

    enum Planet {

        EARTH {
            @Override
            void doSomething(){
                System.out.print(test);
            }
        };

        abstract void doSomething();
    }

    public static void main(String[] args) {
        Universe.Planet.EARTH.doSomething(); // No such property: test for class: groovy.Universe$Planet$1
    }
}

I am aware that this code is also perfect Java code. Though it works as expected using JRE but not with Groovy's runtime environment which makes me even more curious. Is there any proof for the difference? Thanks

Answer 1

Groovy needs some help to find Universe's variable. Here's a link to some official documentation if you want to read up on a few differences between Java and Groovy. Here's an email discussion that touches on this some. For anyone unfamiliar with enums, they're static objects, so no accessing instance objects or variables. Which leads us to our answer, static variable needs to be referenced in a static way (via class, not an instance).
Also, if you try to use inner classes before Groovy 1.7 you're going to have a bad time (you can't).

public class Universe {

static String test = "testing";

enum Planet {

    EARTH {
        @Override
        void doSomething(){
            System.out.print(Universe.test);
        }
    };

    abstract void doSomething();
}

public static void main(String[] args) {
    Universe.Planet.EARTH.doSomething(); // No such property: test for class: groovy.Universe$Planet$1
}
}