How to add element to a list, inside another list?

Question

I have a class named Utilizador created with the following attributes:

private String nome;
private String email;
private String cidadeAtual;
private List<String> checkins = new ArrayList<String>();
private List<String> amigos = new ArrayList<String>();

In my main class I have a list of Utilizadores with the followinf format:

Nickname: Daniel | Email: dd | Cidade atual: Maia | Checkins: [Maia] | Amigos: []
Nickname: Maria | Email: dd2 | Cidade atual: Porto | Checkins: [Porto] | Amigos: []

What I'm trying to do is, type one name and then the other and add a friendship. For example:

I type Daniel, press enter. I type Maria, press enter. The list amigos must now have each others name like this:

Nickname: Daniel | Email: dd | Cidade atual: Maia | Checkins: [Maia] | Amigos: [Maria]
Nickname: Maria | Email: dd2 | Cidade atual: Porto | Checkins: [Porto] | Amigos: [Daniel]

But the method I developed puts both names inside the list Amigos like this:

Nickname: Daniel | Email: dd | Cidade atual: Maia | Checkins: [Maia] | Amigos: [Maria, Daniel]
Nickname: Maria| Email: dd2 | Cidade atual: Porto | Checkins: [Porto] | Amigos: [Maria, Daniel]

Here is the method:

public static void adicionarAmizade() {
    Scanner cu = new Scanner(System.in);
    System.out.println("Introduza o nome dos utilizadores!");
    System.out.println("\n1º:");
    String amigo1 = cu.next();
    System.out.println("\n2º:");
    String amigo2 = cu.next();

    for (Utilizador u : listaUtilizadores) {
        if ((u.getNome()).equals(amigo1)) {
            u.getAmigos().add(amigo2);
            System.out.println("Adicionou");
            System.out.println(u.toString());
            break;
        }
    }

    for (Utilizador u : listaUtilizadores) {
        if ((u.getNome()).equals(amigo2)) {
            u.getAmigos().add(amigo1);
            System.out.println("Adicionou");
            System.out.println(u.toString());
            break;
        }
    }
}

Answer 1

Something like this is a start.

HashMap<String, String> Amigos = new HashMap<>();

//Create Friendship between Marian and Daniel.
Amigos.put("Maria", "Daniel");

//Get Maria's Friend.
System.out.println(Amigos.get("Maria"))

Answer 2

You can also take an object approach.

Person Object

import java.util.ArrayList;


public class Person {
    String name;
    ArrayList<String> friends = new ArrayList();

    Person(String name)
    {
        this.name = name;
    }

    String getName()
    {
        return this.name;
    }

    void addFriend(String friendName)
    {
        friends.add(friendName);
    }

    boolean isFriend(String friendName)
    {
        for(String friend : this.friends)
        {
            if(friend.equals(friendName))
            {
                return true;
            }
        }
        return false;
    }

    String getFriendInPosition(int position)
    {
        return this.friends.get(position);
    }

    int getFriendPosition(String friendName)
    {
        int i = 0;
        for(String friend : this.friends)
        {
            if(friend.equals(friendName))
            {
                return i;
            }
            i++;
        }
        return -1;
    }

    ArrayList<String> getAllFriends()
    {
        return this.friends;
    }
}

Main Class

public static void main(String[] args) {       

  Person maria = new Person("Maria");
  Person daniel = new Person("Daniel");

  maria.addFriend(daniel.getName());
  daniel.addFriend("Maria");//You could create this to add Person objects as friends

  maria.addFriend("me");//You could create this to add Person objects as friends
  maria.addFriend("you");//You could create this to add Person objects as friends

  System.out.println(maria.getFriendInPosition(0));

  System.out.print("Are Maria and Daniel friends? ");
  System.out.println(maria.isFriend(daniel.getName()));

  for(String friend : maria.getAllFriends())
  {
      System.out.println("Maria's friend: " + friend);
  }

  for(String friend : daniel.getAllFriends())
  {
      System.out.println("Daniel's friend: " + friend);
  }
}