A one-to-one relationship between hibernate

There are two types of maintenance for one-to-one relationships, and there are two types of maintenance for one-to-one relationships between primary key associations and unique foreign Key associations: (bidirectional) Association of primary Key associations (bi-directional)  Person.javaPerson {     private string username;    //reference to the accused party     private  address address;    public string getusername ()  {         return username;    }     Public void setusername (String username)  {         this.username = username;    }    public address  GetAddress ()  {        return address;     }    public void setaddress (address address)  {    &NBSP;&NBSP;&NBSP;&NBSP;&NBSP;THIS.ADDRESS=&NBSP;ADDRESS;&NBSP;&NBSP;&NBSP;&NBSP}} (passive side)   Address.javaaddress{    private string addressname;    //reference to the main control party     private  Person person;    public string getaddressname ()  {         return addressname;    }    public  void setaddressname (String addressname)  {         this.addressname= addressname;    }    public person  Getperson ()  {        return person;    }     public void setperson (Person person)  {         this.person= person;    }    public  String tostring ()  {        return new  Tostringbuilder (this).  &nbsP;      append ("Addressname",  addressname) .         tostring ();     }        public  boolean equals (Object o)  {        if  (  ! (o instanceof address)   {             return false;           }         Address rhs =  (address)  o;           return new equalsbuilder ()                            .appendsuper (Super.equals (o))                           .append (This.addressname, rhs.getaddressname ())                            .isequals ();    }    public  Int hashcode ()  {        return new hashcodebuilder (17, 37).         append (Addressname) .         tohashcode ();    }}mapping  file <class name= "person"  table= "Person" ><id name= "id"  type= "long"  column= "id" ><generator class= " Native "/></id><property name=" "username"  column= "username"  type= "string"/>< One-to-onename= ' address ' class= ' address ' cascade= ' all ' constrained= ' false '/></class><class name= "Address"  table= "address" ><id name=" id " column=" id "><generator class=" foreign ">                        <param name= "Property" >person</param>                   </generator>         </id>        <one-to-one name= "Person"  class= "Person"  constrained= "true"/><property name= "Addressname"  column= "AddressName" " type=" string/></class>