Question

public class Base{
        protected String str;

    public static final Base ERROR = new Base("error");
...
}

public class Derived extends Base{
        public static final Derived OTHER = new DERIVED("other");
        public Derived(String str) {
        super(str);
        }
    }

Derived page = Derived.OTHER; //OK
page = (Drived)Derived.ERROR; //ClassCastException

So can I cast static member variable from Base to Derived class?

Answer 1

You can’t.

It is not possible to cast Derived.ERROR to Derived since it’s not an instance of Derived. It’s an instance of Base.

It may help clear up the confusion to realize that Base.ERROR and Derived.ERROR are two ways to refer to the same object.