How can i use enum in an inner class?

Question

I have a PhoneContact class which is an inner class and i need to define an enum for a phone operator. When i try to define it inside the PhoneContact class i get an error. What is the correct way to do this? Code:

public class Contacts {
    class Contact {
        private String date;
        private String type;

        public Contact(String date, String type) {
            LocalDate ld = LocalDate.now();
            String fd = ld.toString();
            this.date = fd;
            this.type = type;
        }

        public boolean isNewerThan(Contact c) {
            if(this.date.compareTo(c.date) <= 0) {
                return true;
            } else {
                return false;
            }
        }

        public String getType() {
            return type;
        }



    }


    class PhoneContact extends Contact {

        private String phone;

        public PhoneContact(String date, String type, String phone) {
            super(date, type);
            this.phone = phone;
        }

        public String getPhone() {
            return phone;
        }
    }


    public static void main(String[] args) {

    }
}