Main

import java.util.List;

sealed interface ListState {}
interface Empty extends ListState { }
interface NonEmpty extends ListState { }

class MyList<ListStatus,E> {
    public List<E> getDelegate() {
        return delegate;
    }

    private List<E> delegate;

    private MyList(List<E> delegate) {
        this.delegate = delegate;
    }

    public static <E> MyList<Empty,E> of() {
        return new MyList<>(List.of());
    }

    public static <E> MyList<NonEmpty,E> of(E e1) {
        return new MyList<>(List.of(e1));
    }

    // other factory methods ...

    public static <E> MyList<Empty,E> addEmpty(MyList<Empty,E> one, MyList<Empty,E> two) {
        return one;
    }

    public static <E> MyList<NonEmpty,E> addToEmpty(MyList<Empty,E> one, MyList<NonEmpty,E> two) {
        return two;
    }

    public static <E> MyList<NonEmpty,E> addEmptyTo(MyList<NonEmpty,E> one, MyList<Empty,E> two) {
        return one;
    }

    public static void main(String[] args) {
        System.out.println(MyList.addEmpty(MyList.of(), MyList.of()));
        System.out.println(MyList.addToEmpty(MyList.of(), MyList.of(1)));
        System.out.println(MyList.addEmptyTo(MyList.of(1), MyList.of()));
    }

    // other methods which use delegate
}