question: public boolean is_same ( Object obj ) { if ( this == obj ) return true ; if ( obj == null ) return false ; if ( getClass ( ) != obj . getClass ( ) ) return false ; HouseNumber other = ( HouseNumber ) obj ; if ( number == null ) { if ( name == null ) { if ( other . name != null ) return false ; } else if ( ! name . equals ( other . name ) ) return false ; } else if ( ! number . equals ( other . number ) ) return false ; if ( street == null ) { if ( other . street != null ) return false ; } else if ( ! street . equals ( other . street ) ) return false ; return true ; }
target:  check if address are content identical If number are equals and street (if number is null, we look at the name)