java - add and share arraylist -

i'm trying create person class has getname() method, addfriend(person r) method, arraylist<person> getfriendlist()

string name; private arraylist person friend = new arraylist person ();  public person(string name) {  this.name=name;      }  public arraylist<person> getfriendlist(){      return friend;  }   public void addfriend(person r){  friend.add(r);  }  friendsoffriends(){         //list of friends of friends of person. }  public static int (p,q){          //return number of friends shared both r , q. } 

public static int numberofmutualfriends(person p, person q){     //return number of friends shared both r , q.       return intersection(p.friend,q.friend).size();  }  public list<person> intersection(list<person> list1, list<person> list2) {     list<person> list = new arraylist<person>();      (person t : list1) {         if(list2.contains(t)) {             list.add(t);         }     }      return list; } 

you'll need redefine hashcode , equals method in order make work.