package chapter11.eight; public class Person { public final String first; public final String last; public final String address; public Person(String first,String last,String address) { this.first=first; this.last=last; this.address=address; } @Override public String toString() { // TODO Auto-generated method stub return "Person:"+first+" "+last+" "+address; } public static class NullPerson extends Person implements Null{ public NullPerson() { super("none", "none", "none"); // TODO Auto-generated constructor stub } @Override public String toString() { // TODO Auto-generated method stub return "NullPerson"; } public static final Person NULL=new NullPerson(); } }