Enum NullPointerException

Question

Could anyone explain why

public class Testabut{
    enum ThreeColors{RED, BLUE, green;
        public void woowoo(){
        System.out.println("woo");}
    }
     ThreeColors color;



    class Innerclass{
        Innerclass(){
             color.woowoo();
        }
    }

generates a null pointer exception at the invocation of woowoo() ? The instance of color should be reachable, no?

Answer 1

Because color is not initialized and it's default value is null.
Initialize it like

ThreeColors color = ThreeColors.RED;  //Or any other value

Answer 2

Your color variable is null. You have to initialize it to use it.