package persons;

import java.io.Serializable;

interface Person extends Serializable {
   String getFirstName();
   String getLastName();
  }

public final class PersonImpl {
   private PersonImpl() throws UnsupportedOperationException {
    throw new UnsupportedOperationException();
 }

public static Person getPerson(final String firstName
, final String lastName)
throws NullPointerException {
   if(firstName == null || lastName == null) {
   throw new NullPointerException();
   }
   else {
   return new _Person(firstName, lastName);
   }
   }

private static final class _Person implements Person {
   private final String firstName;
   private final String lastName;

_Person(final String firstName, final String lastName) {
   this.firstName = firstName;
   this.lastName = lastName;
  }

public String getFirstName() {
   return firstName;
  }

public String getLastName() {
   return lastName;
  }

@Override
  public boolean equals(final Object o) {
  if(this == o) {
  return true;
 }
 else if(!(o instanceof Person)) {
   return false;
 }
 else {
   final Person p = (Person)o;
   return firstName.equals(p.getFirstName()) && lastName.equals(p.getLastName());
 }
}

@Override
  public int hashCode() {
  // let's make it simple... don't know about you, but I'm out of breath :)
  return firstName.hashCode() ^ lastName.hashCode();
   } 
 }
}